MFS SERIES TRUST IV
485BPOS, 1998-11-30
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<PAGE>   1
   
       As filed with the Securities and Exchange Commission on November 30, 1998
                                                       1933 Act File No. 2-54607
                                                      1940 Act File No. 811-2594
    


                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549
                               ------------------

   
                                    FORM N-1A
                             REGISTRATION STATEMENT
                                      UNDER
                           THE SECURITIES ACT OF 1933
                         POST-EFFECTIVE AMENDMENT NO. 33
                                       AND
                             REGISTRATION STATEMENT
                                      UNDER
                       THE INVESTMENT COMPANY ACT OF 1940
                                AMENDMENT NO. 29
    

                               MFS SERIES TRUST IV
               (Exact Name of Registrant as Specified in Charter)

                500 Boylston, Street, Boston, Massachusetts 02116
                    (Address of Principal Executive Offices)

        Registrant's Telephone Number, Including Area Code: 617-954-5000
           Stephen E. Cavan, Massachusetts Financial Services Company,
                500 Boylston Street, Boston, Massachusetts 02116
                     (Name and Address of Agent for Service)

                  APPROXIMATE DATE OF PROPOSED PUBLIC OFFERING:
  It is proposed that this filing will become effective (check appropriate box)

   
         |_| immediately upon filing pursuant to paragraph (b)
         |X| on December 29, 1998 pursuant to paragraph (b)
         |_| 60 days after filing pursuant to paragraph (a)(i)
         |_| on [date] pursuant to paragraph (a)(i)
         |_| 75 days after filing pursuant to paragraph (a)(ii)
         |_| on [date] pursuant to paragraph (a)(ii) of rule 485.
    

         If appropriate, check the following box:

         |_| this post-effective amendment designates a new effective date for a
         previously filed post-effective amendment
<PAGE>   2
                               MFS SERIES TRUST IV

                              MFS MONEY MARKET FUND
                        MFS GOVERNMENT MONEY MARKET FUND
                             MFS MUNICIPAL BOND FUND
                 MFS MID CAP GROWTH FUND (FORMERLY MFS OTC FUND)



                              CROSS REFERENCE SHEET


(Pursuant to Rule 404 showing location in Prospectus and/or Statement of
Additional Information of the responses to the Items in Parts A and B of Form
N-1A)

   
<TABLE>
<CAPTION>
                                                                                    STATEMENT OF
  ITEM NUMBER                                                                        ADDITIONAL
FORM N-1A, PART A                 PROSPECTUS CAPTION                             INFORMATION CAPTION
- -----------------                 ------------------                             -------------------
<S>                              <C>                                             <C>
      1     (a), (b)             Cover Page                                             *

      2     (a)                  Expense Summary                                        *

            (b), (c)                        *                                           *

      3     (a)                  Condensed Financial Information                        *

            (b)                             *                                           *

            (c)                  Information Concerning Shares                          *
                                   of the Fund - Performance
                                   Information

            (d)                  Condensed Financial Information                        *

      4     (a)                  The Fund; Investment Objective                         *
                                   and Policies

            (b), (c)             Investment Objective and                               *
                                   Policies; Year 2000 Issues

      5     (a)                  The Fund; Management of the                            *
                                   Fund - Investment Adviser
</TABLE>
    
<PAGE>   3
<TABLE>
<CAPTION>
                                                                                            STATEMENT OF
  ITEM NUMBER                                                                                ADDITIONAL
FORM N-1A, PART A                   PROSPECTUS CAPTION                                   INFORMATION CAPTION
- -----------------                   ------------------                                   -------------------
<S>                              <C>                                                     <C>
            (b)                  Front Cover Page; Management                                       *
                                   of the Fund - Investment Adviser;
                                   Back Cover Page

            (c)                  Management of the Fund -                                           *
                                   Investment Adviser

            (d)                  Management of the Fund -                                           *
                                   Administrator

            (e)                  Management of the Fund -                                           *
                                   Shareholder Servicing Agent;
                                   Back Cover Page

            (f)                  Expense Summary; Condensed                                         *
                                   Financial Information; Expenses

            (g)                  Investment Objective and                                           *
                                   Policies - Portfolio Trading

            (h)                                 *                                                   *

      5A    (a), (b), (c)                       **                                                 **

      6     (a)                  Information Concerning Shares of                                   *
                                   the Fund - Description of Shares,
                                   Voting Rights and Liabilities;
                                   Information Concerning Shares of
                                   the Fund - Redemptions and
                                   Repurchases; Information
                                   Concerning Shares of the Fund -
                                   Purchases; Information Concerning
                                   Shares of the Fund - Exchanges

            (b), (c), (d)                           *                                               *

            (e)                  Shareholder Services                                               *

            (f)                  Information Concerning Shares of                                   *
                                   the Fund - Distributions; Shareholder
                                 Services - Distribution Options
</TABLE>
<PAGE>   4
   
<TABLE>
<CAPTION>
                                                                                    STATEMENT OF
      ITEM NUMBER                                                                    ADDITIONAL
    FORM N-1A, PART A                PROSPECTUS CAPTION                           INFORMATION CAPTION
    -----------------                ------------------                           -------------------
<S>                              <C>                                              <C>
            (g)                  Information Concerning Shares of                        *
                                   the Fund - Tax Status;
                                   Information Concerning Shares
                                   of the Fund - Distributions

            (h)                                     *                                    *

      7     (a)                  Front Cover Page; Management                            *
                                   of the Fund - Distributor; Back
                                   Cover Page

            (b)                  Information Concerning Shares of                        *
                                   the Fund - Purchases; Information
                                   Concerning Shares of the Fund -
                                   Net Asset Value; Year 2000 Issue

            (c)                  Information Concerning Shares of                        *
                                   the Fund - Purchases; Information
                                   Concerning Shares of the Fund -
                                   Exchanges; Shareholder Services

            (d)                  Front Cover Page; Information                           *
                                   Concerning Shares of the Fund -
                                   Purchases; Shareholder Services

            (e)                  Information Concerning Shares of                        *
                                   the Fund - Distribution Plan;
                                   Expense Summary; Information
                                   Concerning Shares of the Fund -
                                   Purchases

            (f)                  Information Concerning Shares of                        *
                                   the Fund - Distribution Plan
</TABLE>
    
<PAGE>   5
<TABLE>
<CAPTION>
                                                                                        STATEMENT OF
       ITEM NUMBER                                                                        ADDITIONAL
    FORM N-1A, PART A              PROSPECTUS CAPTION                                 INFORMATION CAPTION
    -----------------              ------------------                                 -------------------
<S>                              <C>                                                  <C>
            (g)                  Expense Summary; Information                                 *
                                   Concerning Shares of the Fund -
                                   Purchases; Information Concerning
                                   Shares of the Fund - Exchanges; Information
                                   Concerning Shares of the Fund - Redemptions
                                   and Repurchases; Information Concerning
                                   Shares of the Fund Distribution Plan;
                                   Information Concerning Shares of the Fund
                                   Distributions; Information Concerning Shares
                                   of the Fund Performance Information;
                                   Shareholder Services

      8     (a)                  Information Concerning Shares of                             *
                                   the Fund - Redemptions and
                                   Repurchases; Information
                                   Concerning Shares of the Fund -
                                   Purchases

            (b), (c), (d)        Information Concerning Shares of                             *
                                   the Fund - Redemptions and
                                   Repurchases

      9                                             *                                         *
</TABLE>
<PAGE>   6
<TABLE>
<CAPTION>
                                                                                STATEMENT OF
      ITEM NUMBER                                                                 ADDITIONAL
   FORM N-1A, PART B                       PROSPECTUS CAPTION                   INFORMATION CAPTION
   -----------------                       ------------------                   -------------------
<S>                             <C>                                            <C>
     10     (a), (b)                                *                            Front Cover Page

     11                                             *                            Front Cover Page

     12                                             *                            Definitions

     13     (a), (b), (c)                           *                            Investment Objective,
                                                                                 Policies and Restrictions

            (d)                                     *                                      *

     14     (a), (b)                                *                            Management of the Fund -
                                                                                  Trustees and Officers

            (c)                                     *                            Management of the Fund -
                                                                                  Trustees and Officers;
                                                                                  Trustee Compensation
                                                                                  Table

     15     (a)                                     *                                     *

            (b), (c)                                *                            Management of the Fund -
                                                                                  Trustees and Officers

     16     (a)                  Management of the Fund -                        Management of the Fund -
                                   Investment Adviser                             Investment Adviser;
                                                                                   Management of the Fund -
                                                                                  Trustees and Officers

            (b)                  Management of the Fund -                        Management of the Fund -
                                   Investment Adviser                             Investment Adviser

            (c)                                     *                                     *

            (d)                                     *                            Management of the Fund -
                                                                                  Investment Adviser;
                                                                                  Administrator


            (e)                                     *                            Portfolio Transactions
                                                                                  and Brokerage Commissions
</TABLE>
<PAGE>   7
<TABLE>
<CAPTION>
                                                                                  STATEMENT OF
      ITEM NUMBER                                                                  ADDITIONAL
    FORM N-1A, PART B                    PROSPECTUS CAPTION                     INFORMATION CAPTION
    -----------------                    ------------------                     -------------------
<S>                             <C>                                            <C>
            (f)                       Information Concerning Shares             Distribution Plan
                                       of the Fund - Distribution
                                        Plan

            (g)                                 *                                          *

            (h)                                 *                               Management of the Fund -
                                                                                  Custodian; Independent
                                                                                  Auditors and Financial
                                                                                  Statements; Back Cover
                                                                                  Page

            (i)                                 *                               Management of the Fund -
                                                                                  Shareholder Servicing
                                                                                  Agent

     17     (a), (b), (c),                      *                               Portfolio Transactions
            (d), (e)                                                              and Brokerage
                                                                                  Commissions

     18     (a)                  Information Concerning Shares                  Description of Shares,
                                   of the Fund - Description of                   Voting Rights and
                                   Shares, Voting Rights and                      Liabilities
                                   Liabilities

            (b)                                 *                                          *

     19     (a)                  Information Concerning Shares                  Shareholder Services
                                   of the Fund - Purchases;
                                   Shareholder Services

            (b)                  Information Concerning Shares                  Management of the Fund -
                                   of the Fund - Net Asset Value;                 Distributor;
                                   Information Concerning Shares                  Determination of Net
                                   of the Fund - Purchases                        Asset Value and
                                                                                  Performance - Net Asset
                                                                                  Value

            (c)                                 *                                          *

     20                                         *                               Tax Status
</TABLE>
<PAGE>   8
<TABLE>
<CAPTION>
                                                                             STATEMENT OF
    ITEM NUMBER                                                               ADDITIONAL
  FORM N-1A, PART B                   PROSPECTUS CAPTION                 INFORMATION CAPTION
  -----------------                   ------------------                 -------------------
<S>                                   <C>                                <C>
     21     (a), (b)                        *                            Management of the Fund -
                                                                          Distributor; Distribution
                                                                          Plan

            (c)                             *                                    *

     22     (a)                             *                                    *

            (b)                             *                            Determination of Net
                                                                          Asset Value and
                                                                          Performance; Appendix A

     23                                     *                            Independent Auditors
                                                                         and Financial Statements
</TABLE>

- -------------
*    Not Applicable
**   Contained in Annual Report
<PAGE>   9
 
MFS(R) MONEY MARKET FUND
MFS(R) GOVERNMENT MONEY
MARKET FUND
 
(Members of the MFS Family of Funds(R))
                                                                      PROSPECTUS
   
                                                                 JANUARY 1, 1999
    
                                                   SHARES OF BENEFICIAL INTEREST
 
- --------------------------------------------------------------------------------
500 Boylston Street, Boston, Massachusetts 02116      (617) 954-5000
 
   
This Prospectus pertains to the MFS Money Market Fund and the MFS Government
Money Market Fund (collectively referred to as either the "Money Market Funds"
or the "Funds"), each a series of MFS Series Trust IV (the "Trust"). The Trust
presently consists of four series of shares, each of which represents a separate
portfolio with separate investment policies. The investment objective of each of
the Money Market Funds is to seek as high a level of current income as is
considered consistent with the preservation of capital and liquidity. The MFS
Money Market Fund seeks to achieve its investment objective by investing
primarily in short-term money market instruments, including U.S. Government
securities and repurchase agreements collateralized by such securities,
obligations of the larger banks, prime commercial paper and high quality
corporate obligations. The MFS Government Money Market Fund seeks to achieve its
investment objective by investing only in short-term securities issued or
guaranteed by the U.S. Treasury or agencies or instrumentalities of the U.S.
Government and repurchase agreements collateralized by such securities. See
"Investment Objective and Policies." The minimum initial investment in a Fund is
generally $1,000 per account (see "Information Concerning Shares of the Funds --
Purchases").
    
 
The investment adviser and distributor for each Fund is Massachusetts Financial
Services Company ("MFS" or the "Adviser") and MFS Fund Distributors, Inc.
("MFD"), respectively, both of which are located at 500 Boylston Street, Boston,
Massachusetts 02116.
                                                        (continued on next page)
 
INVESTMENTS IN THE FUNDS ARE NEITHER INSURED NOR GUARANTEED BY THE U.S.
GOVERNMENT AND THERE IS NO ASSURANCE THAT THE FUNDS WILL BE ABLE TO MAINTAIN A
STABLE NET ASSET VALUE OF $1.00 PER SHARE.

  THESE SECURITIES HAVE NOT BEEN APPROVED OR DISAPPROVED BY THE SECURITIES AND
 EXCHANGE COMMISSION OR ANY STATE SECURITIES COMMISSION NOR HAS THE SECURITIES
   AND EXCHANGE COMMISSION OR ANY STATE SECURITIES COMMISSION PASSED UPON THE
          ACCURACY OR ADEQUACY OF THIS PROSPECTUS. ANY REPRESENTATION
                     TO THE CONTRARY IS A CRIMINAL OFFENSE.
 
   INVESTORS SHOULD READ THIS PROSPECTUS AND RETAIN IT FOR FUTURE REFERENCE.
<PAGE>   10
 
(continued from previous page)
 
   
This Prospectus sets forth concisely the information concerning the Funds that a
prospective investor ought to know before investing. The Funds have filed with
the Securities and Exchange Commission (the "SEC") a Statement of Additional
Information, dated January 1, 1999, as amended or supplemented from time to time
(the "SAI"), which contains more detailed information about each of the Funds.
The SAI is incorporated into this Prospectus by reference. See page 21 for a
further description of the information set forth in the SAI. A copy of the SAI
may be obtained without charge by contacting the Shareholder Servicing Agent
(see back cover for address and phone number). The SEC maintains an Internet
World Wide Web site (http://www.sec.gov) that contains the SAI, materials that
are incorporated by reference into this Prospectus and the SAI, and other
information regarding the Funds. This Prospectus is available on the Adviser's
Internet World Wide Web site at http://www.mfs.com.
    
 
TABLE OF CONTENTS
 
   
<TABLE>
<CAPTION>
                                                                   PAGE
                                                                   ----
<S>  <C>                                                           <C>
1.   Expense Summary.............................................     3
2.   Condensed Financial Information.............................     4
3.   The Funds...................................................     8
4.   Investment Objective and Policies...........................     8
5.   Management of the Funds.....................................    10
6.   Year 2000 Issues............................................    11
7.   Information Concerning Shares of the Funds..................    11
     Purchases...................................................    11
     Exchanges...................................................    13
     Redemptions.................................................    14
     Determination of Net Asset Value............................    16
     Distributions...............................................    17
     Tax Status..................................................    17
     Description of Shares, Voting Rights and Liabilities........    18
     Performance Information.....................................    18
     Provision of Annual and Semiannual Reports..................    19
8.   Shareholder Services........................................    19
     Appendix A..................................................   A-1
</TABLE>
    
 
                                        2
<PAGE>   11
 
1.  EXPENSE SUMMARY
 
SHAREHOLDER TRANSACTION EXPENSES FOR EACH FUND:
 
    Maximum Sales Load Imposed on Purchases of Shares...................None
    Maximum Contingent Deferred Sales Charge....................See Below(1)
 
ANNUAL OPERATING EXPENSES OF THE FUNDS (AS A PERCENTAGE OF AVERAGE NET ASSETS):
 
   
<TABLE>
<CAPTION>
                                         MFS MONEY      MFS GOVERNMENT
                                        MARKET FUND    MONEY MARKET FUND
                                        -----------    -----------------
<S>                                     <C>            <C>
Management Fees.......................     0.47%             0.50%
Other Expenses(2).....................     0.27%             0.38%
                                           ----              ----
Total Operating Expenses..............     0.74%             0.88%
</TABLE>
    
 
- ---------------
(1) A contingent deferred sales charge ("CDSC") of 1% will be imposed with
    respect to the redemption of Fund shares in the event that (i) the shares
    redeemed were exchanged from another fund in the MFS Family of Funds which
    carried a CDSC which carried over to the Fund shares redeemed, and (ii) the
    CDSC period had not expired at the time of the redemption of Fund shares
    (see "Exchanges" and "Redemptions" below).
(2) Each Fund has an expense offset arrangement which reduces the Fund's
    custodian fee based upon the amount of cash maintained by the Fund with its
    custodian and dividend disbursing agent, and may enter into other such
    arrangements and directed brokerage arrangements (which would also have the
    effect of reducing the Fund's expenses). Any such fee reductions are not
    reflected under "Other Expenses."
 
                              EXAMPLE OF EXPENSES
 
An investor would pay the following dollar amounts of expenses on a hypothetical
$1,000 investment in a Fund, assuming (1) a 5% annual return and (2) redemption
at the end of each of the time periods indicated:
 
   
<TABLE>
<CAPTION>
                                               1 YEAR   3 YEARS   5 YEARS   10 YEARS
                                               ------   -------   -------   --------
<S>                                            <C>      <C>       <C>       <C>
MFS MONEY MARKET
  FUND                                           $8       $24       $41       $ 92
MFS GOVERNMENT
  MONEY MARKET FUND                              $9       $28       $49       $108
</TABLE>
    
 
    The purpose of the expense table provided above is to assist investors in
understanding the various costs and expenses that a shareholder in a Fund will
bear directly or indirectly. A more complete description of management fees of
the Funds is set forth in "Management of the Funds -- Investment Adviser."
 
THE "EXAMPLE" SET FORTH ABOVE SHOULD NOT BE CONSIDERED A REPRESENTATION OF PAST
OR FUTURE EXPENSES OF A FUND; ACTUAL EXPENSES MAY BE GREATER OR LESS THAN THOSE
SHOWN.
 
                                        3
<PAGE>   12
 
2.  CONDENSED FINANCIAL INFORMATION
 
The following information has been audited for at least the latest five fiscal
years of the Funds and should be read in conjunction with the financial
statements included in the Funds' Annual Report to Shareholders which are
incorporated by reference into the SAI in reliance upon the report of the Funds'
independent auditors, given upon their authority as experts in accounting and
auditing. Each Fund's current independent auditors are Deloitte & Touche LLP.
 
   
                              FINANCIAL HIGHLIGHTS
    
   
                             MFS MONEY MARKET FUND
    
 
   
<TABLE>
<CAPTION>
                                                                                TEN MONTHS
                                             YEAR ENDED AUGUST 31,                ENDED      YEAR ENDED
                                  -------------------------------------------   AUGUST 31,   OCTOBER 31,
                                     1998        1997       1996       1995        1994         1993
                                     ----        ----       ----       ----     ----------   -----------
<S>                               <C>          <C>        <C>        <C>        <C>          <C>
Per share data (for a share
 outstanding throughout each
 period):
Net asset value -- beginning of
 period.........................  $     1.00   $   1.00   $   1.00   $   1.00    $   1.00     $   1.00
                                  ----------   --------   --------   --------    --------     --------
Income from investment
 operations --
   Net investment income........  $     0.05   $   0.05   $   0.05   $   0.05    $   0.02     $   0.02
Less distributions declared to
 shareholders from net
 investment income..............       (0.05)     (0.05)     (0.05)     (0.05)      (0.02)       (0.02)
                                  ----------   --------   --------   --------    --------     --------
Net asset value -- end of
 period.........................  $     1.00   $   1.00   $   1.00   $   1.00    $   1.00     $   1.00
                                  ==========   ========   ========   ========    ========     ========
Total return....................       5.03%      4.61%      4.86%      5.04%       2.91%+       2.39%
Ratios (to average net assets)/
 Supplemental data:
   Expenses##...................       0.74%      0.80%      0.79%      0.76%       0.78%+       0.83%
   Net investment income........       4.88%      4.71%      4.78%      4.92%       2.95%+       2.39%
Net assets at end of period (000
 omitted).......................  $1,071,113   $634,240   $644,205   $410,798    $435,780     $350,316
</TABLE>
    
 
- ---------------
 
   
<TABLE>
<C>  <S>
  +  Annualized.
 ##  For fiscal years ending after September 1, 1995, the Fund's
     expenses are calculated without reduction for fees paid
     indirectly.
</TABLE>
    
 
                                        4
<PAGE>   13
 
   
                              FINANCIAL HIGHLIGHTS
    
   
                             MFS MONEY MARKET FUND
    
 
   
<TABLE>
<CAPTION>
                                                       YEAR ENDED OCTOBER 31,
                                        ----------------------------------------------------
                                          1992       1991       1990       1989       1988
                                          ----       ----       ----       ----       ----
<S>                                     <C>        <C>        <C>        <C>        <C>
Per share data (for a share
  outstanding throughout each period):
Net asset value -- beginning of
  period..............................  $   1.00   $   1.00   $   1.00   $   1.00   $   1.00
                                        --------   --------   --------   --------   --------
Income from investment operations --
    Net investment income.............  $   0.03   $   0.06   $   0.07   $   0.08   $   0.07
Less distributions declared to
  shareholders from net investment
  income..............................     (0.03)     (0.06)     (0.07)     (0.08)     (0.07)
                                        --------   --------   --------   --------   --------
Net asset value -- end of period......  $   1.00   $   1.00   $   1.00   $   1.00   $   1.00
                                        ========   ========   ========   ========   ========
Total return..........................     3.35%      6.07%      7.99%      8.84%      7.12%
Ratios (to average net
  assets)/Supplemental data:
    Expenses..........................     0.87%      0.82%      0.76%      0.83%      0.83%
    Net investment income.............     3.36%      5.94%      7.60%      8.45%      6.72%
Net assets at end of period (000
  omitted)............................  $448,825   $541,945   $677,164   $676,382   $664,895
</TABLE>
    
 
                                        5
<PAGE>   14
 
   
                              FINANCIAL HIGHLIGHTS
    
   
                        MFS GOVERNMENT MONEY MARKET FUND
    
 
   
<TABLE>
<CAPTION>
                                                                            TEN MONTHS
                                            YEAR ENDED AUGUST 31,             ENDED      YEAR ENDED
                                    -------------------------------------   AUGUST 31,   OCTOBER 31,
                                     1998      1997      1996      1995        1994         1993
                                     ----      ----      ----      ----     ----------   -----------
<S>                                 <C>       <C>       <C>       <C>       <C>          <C>
Per share data (for a share
  outstanding throughout each
  period):
Net asset value -- beginning of
  period..........................  $  1.00   $  1.00   $  1.00   $  1.00    $  1.00       $  1.00
                                    -------   -------   -------   -------    -------       -------
Income from investment
  operations --
    Net investment income.........  $  0.05   $  0.05   $  0.05   $  0.05    $  0.02       $  0.02
Less distributions declared to
  shareholders from net investment
  income..........................    (0.05)    (0.05)    (0.05)    (0.05)     (0.02)        (0.02)
                                    -------   -------   -------   -------    -------       -------
Net asset value -- end of
  period..........................  $  1.00   $  1.00   $  1.00   $  1.00    $  1.00       $  1.00
                                    =======   =======   =======   =======    =======       =======
Total return......................    4.85%     4.81%     4.73%     4.92%      2.64%+        2.33%
Ratios (to average net assets)/
  Supplemental data:
    Expenses##....................    0.88%     0.85%     0.89%     0.84%      1.05%+        0.99%
    Net investment income.........    4.70%     4.02%     4.64%     4.82%      2.64%+        2.20%
Net assets at end of period (000
  omitted)........................  $44,843   $38,387   $42,499   $38,440    $38,347       $35,576
</TABLE>
    
 
- ---------------
 
   
<TABLE>
<C>  <S>
  +  Annualized.
 ##  For fiscal years ending after September 1, 1995, the Fund's
     expenses are calculated without reduction for fees paid
     indirectly.
</TABLE>
    
 
                                        6
<PAGE>   15
 
   
                              FINANCIAL HIGHLIGHTS
    
   
                        MFS GOVERNMENT MONEY MARKET FUND
    
 
   
<TABLE>
<CAPTION>
                                                         YEAR ENDED OCTOBER 31,
                                             -----------------------------------------------
                                              1992      1991      1990      1989      1988
                                              ----      ----      ----      ----      ----
<S>                                          <C>       <C>       <C>       <C>       <C>
Per share data (for a share outstanding
  throughout each period):
Net asset value -- beginning of period.....  $  1.00   $  1.00   $  1.00   $  1.00   $  1.00
                                             -------   -------   -------   -------   -------
Income from investment operations --
    Net investment income..................  $  0.03   $  0.06   $  0.07   $  0.08   $  0.06
Less distributions declared to shareholders
  from net investment income...............    (0.03)    (0.06)    (0.07)    (0.08)    (0.06)
                                             -------   -------   -------   -------   -------
Net asset value -- end of period...........  $  1.00   $  1.00   $  1.00   $  1.00   $  1.00
                                             =======   =======   =======   =======   =======
Total return...............................    3.27%     5.68%     7.55%     8.61%     6.47%
Ratios (to average net assets)/Supplemental
  data:
    Expenses...............................    0.87%     0.83%     0.80%     0.85%     0.74%
    Net investment income..................    3.28%     5.53%     7.34%     8.29%     6.29%
Net assets at end of period (000
  omitted).................................  $47,629   $50,655   $53,701   $51,619   $50,343
</TABLE>
    
 
                                        7
<PAGE>   16
 
3.  THE FUND
 
The Funds are diversified series of the Trust, an open-end management investment
company which was organized as a business trust under the laws of The
Commonwealth of Massachusetts in 1975. The Trust presently consists of four
series of shares, each of which represents a portfolio with separate investment
policies. Shares of the Funds are continuously sold to the public and the Funds
use the proceeds to buy money market instruments for the Fund for which such
shares were sold. The Trust's Board of Trustees provides board supervision over
the affairs of the Trust. A majority of the Trustees of the Trust are not
affiliated with the Adviser. The Adviser is responsible for the management of
each Fund's assets and the officers of the Trust are responsible for the
operations of each Fund. The Adviser manages each Fund from day to day in
accordance with the investment objective and the investment policies of that
Fund. The selection of investments and the way they are managed depend on the
conditions and trends in the economy and the financial marketplaces. Each Fund
also offers to buy back (redeem) its shares from its shareholders at any time at
net asset value.
 
4.  INVESTMENT OBJECTIVE AND POLICIES
 
INVESTMENT OBJECTIVE -- The investment objective of each Fund is to seek as high
a level of current income as is considered consistent with the preservation of
capital and liquidity. The investment objective of a Fund will not be changed
without first obtaining shareholder approval from the shareholders of that Fund.
Any investment involves risk and there can be no assurance that either Fund will
achieve its investment objective.
 
INVESTMENT POLICIES -- The MFS Money Market Fund seeks to achieve its investment
objective by investing primarily (i.e., at least 80% of its assets under normal
circumstances) in the following instruments:
 
        (i) obligations issued or guaranteed as to interest and principal by the
    U.S. Government or any agency or instrumentality thereof (including
    repurchase agreements collateralized by such securities);
 
        (ii) obligations of banks (including certificates of deposit and
    bankers' acceptances) which at the date of investment have capital, surplus,
    and undivided profits (as of the date of their most recently published
    financial statements) in excess of $100,000,000; and obligations of other
    banks or savings and loan associations if such obligations are insured by
    the Federal Deposit Insurance Corporation, provided that not more than 10%
    of the total assets of the MFS Money Market Fund will be invested in such
    insured obligations;
 
   
        (iii) commercial paper which at the date of investment is rated A-1 by
    Standard & Poor's Ratings Services ("S&P"), F1 by Fitch IBCA ("Fitch") or
    P-1 by Moody's Investors Service, Inc. ("Moody's"), or, if not rated, is
    issued or guaranteed as to payment of principal and interest by companies
    which at the date of investment have an outstanding debt issue rated AA or
    better by S&P or Fitch or Aa or better by Moody's; and
    
 
        (iv) short-term (maturing in 13 months or less) corporate obligations
    which at the date of investment are rated AA or better by S&P or Fitch or Aa
    or better by Moody's.
 
The MFS Money Market Fund may also invest up to 20% of its assets in debt
instruments not specifically described in (i) through (iv) above, provided that
such instruments are deemed by the Trustees of the Trust to be of comparable
high quality and liquidity. The MFS Money Market



                                        8
<PAGE>   17
 
Fund may invest its assets in the securities of foreign issuers and in the
securities of foreign branches of U.S. banks such as negotiable certificates of
deposit (Eurodollars). Since the portfolio of the MFS Money Market Fund may
contain such securities, an investment therein may involve a greater degree of
risk than an investment in the MFS Government Money Market Fund or in a fund
which invests only in debt obligations of U.S. domestic issuers, due to the
possibility that there may be less publicly available information concerning
foreign issuers, more volatile markets, less securities regulation, less
favorable tax provisions, war or expropriation.
 
In addition, the MFS Money Market Fund may invest up to 75% of its assets in all
finance companies as a group, all banks and bank holding companies as a group
and all utility companies as a group when in the opinion of management yield
differentials and money market conditions suggest such investments are advisable
and when cash is available for such investments and instruments are available
for purchase which fulfill the Fund's objective in terms of quality and
marketability.
 
The MFS Government Money Market Fund seeks to achieve its investment objective
by investing only in securities issued or guaranteed as to principal and
interest by the U.S. Treasury or agencies or instrumentalities of the U.S.
Government (including repurchase agreements collateralized by such securities).
                            ------------------------
 
For a description of the instruments discussed above and the risks associated
with investments in repurchase agreements, see Appendix A to this Prospectus.
For a description of the ratings discussed above see Appendix A to the SAI.
 
All the assets of both the MFS Money Market Fund and the MFS Government Money
Market Fund will be invested in obligations which mature in 13 months or less
and substantially all of these investments will be held to maturity; however,
securities collateralizing repurchase agreements may have maturities in excess
of 13 months. Both the MFS Money Market Fund and the MFS Government Money Market
Fund will, to the extent feasible, make portfolio investments primarily in
anticipation of or in response to changing economic and money market conditions
and trends. Currently, the dollar weighted average maturity of the investments
of either Fund may not exceed 90 days.
 
The SAI includes a discussion of specific investment restrictions which govern
the investment policies of each Fund. The specific investment restrictions
listed in the SAI may be changed without shareholder approval unless indicated
otherwise. See "Investment Objective, Policies and Restrictions -- Investment
Restrictions" in the SAI. Except with respect to each Fund's policy on
borrowing, each Fund's investment limitations, policies and rating standards are
adhered to at the time of purchase or utilization of assets subject to
compliance with the Investment Company Act of 1940, as amended, and rules
adopted thereunder (the "1940 Act"); a subsequent change in circumstances will
not be considered to result in a violation of policy.
 
                                        9
<PAGE>   18
 
5.  MANAGEMENT OF THE FUNDS
 
   
INVESTMENT ADVISER -- MFS manages each Fund pursuant to an Investment Advisory
Agreement dated August 1, 1993 (the "Advisory Agreement"). Under the Advisory
Agreement, the Adviser provides each Fund with overall investment advisory
services. Subject to such policies as the Trustees may determine, the Adviser
makes investment decisions for each Fund. For these services and facilities, the
Adviser receives a management fee computed and paid monthly at an annual rate
equal to 0.5% of the first $300 million of the average aggregate daily net
assets of the MFS Government Money Market Fund and the MFS Money Market Fund;
0.45% of the next $400 million of such assets; 0.4% of the next $300 million of
such assets; and 0.35% of such assets in excess of $1 billion. For the Trust's
fiscal year ended August 31, 1998, MFS received fees under the Advisory
Agreement of $3,293,238 and $238,557 from the MFS Money Market Fund and MFS
Government Money Market Fund, respectively, the total of which is equivalent, on
an annualized basis, to 0.47% and 0.50% of the MFS Money Market Fund's and MFS
Government Money Market Fund's average daily net assets, respectively.
    
 
   
MFS also serves as investment adviser to the other funds in the MFS Family of
Funds (the "MFS Funds"), to MFS(R) Municipal Income Trust, MFS Multimarket
Income Trust, MFS Government Markets Income Trust, MFS Intermediate Income
Trust, MFS Charter Income Trust, MFS Special Value Trust, MFS Institutional
Trust, MFS Variable Insurance Trust, MFS/Sun Life Series Trust and seven
variable accounts, each of which is a registered investment company established
by Sun Life Assurance Company of Canada (U.S.), a subsidiary of Sun Life
Assurance Company of Canada ("Sun Life") in connection with the sale of various
fixed/variable annuity contracts. MFS and its wholly owned subsidiary, MFS
Institutional Advisors, Inc., provide investment advice to substantial private
clients.
    
 
   
MFS is America's oldest mutual fund organization. MFS and its predecessor
organizations have a history of money management dating from 1924 and the
founding of the first mutual fund in the United States, Massachusetts Investors
Trust. Net assets under the management of the MFS organization were
approximately $83.1 billion on behalf of approximately 3.5 million investor
accounts as of September 30, 1998. As of such date, the MFS organization managed
approximately $20.6 billion of assets in fixed income securities and
approximately $54.6 billion of assets in equity securities. MFS is a subsidiary
of Sun Life of Canada (U.S.) Financial Services Holdings, Inc., which in turn is
an indirect wholly owned subsidiary of Sun Life. The Directors of MFS are John
W. Ballen, Thomas J. Cashman, Joseph W. Dello Russo, John D. McNeil, Kevin R.
Parke, Arnold D. Scott, William W. Scott, Jr., Jeffrey L. Shames and Donald A.
Stewart. Mr. Shames is the Chairman and Chief Executive Officer of MFS, Mr.
Ballen is the President and the Chief Investment Officer of MFS, Mr. Cashman is
an Executive Vice President of MFS, Mr. Dello Russo is the Chief Financial
Officer and an Executive Vice President of MFS, Mr. Parke is the Chief Equity
Officer, Director of Equity Research and an Executive Vice President of MFS, Mr.
Arnold Scott is the Secretary and a Senior Executive Vice President of MFS and
Mr. William Scott is the President of MFS Fund Distributors Inc., the
distributor of MFS Funds. Messrs. McNeil and Stewart are the Chairman and
President, respectively, of Sun Life. Sun Life, a mutual life insurance company,
is one of the largest international life insurance companies and has been
operating in the U.S. since 1895, establishing a headquarters office here in
1973. The executive officers of MFS report to the Chairman of Sun Life.
    
 
                                       10
<PAGE>   19
 
   
Mr. Shames, the Chairman of MFS, is also a Trustee of the Trust. W. Thomas
London, Stephen E. Cavan, James O. Yost, James R. Bordewick, Jr., Geoffrey L.
Kurinsky, Ellen Moynihan and Mark E. Bradley, all of whom are officers of MFS,
are officers of the Trust.
    
 
In certain instances there may be securities which are suitable for the Fund's
portfolio as well as for portfolios of other clients of MFS. Some simultaneous
transactions are inevitable when several clients receive investment advice from
MFS, particularly when the same security is suitable for more than one client.
While in some cases this arrangement could have a detrimental effect on the
price or availability of the security as far as the Fund is concerned, in other
cases, it may produce increased investment opportunities for the Fund.
 
ADMINISTRATOR -- MFS provides each Fund with certain financial, legal,
compliance, shareholder communications and other administrative services
pursuant to a Master Administrative Services Agreement dated March 1, 1997, as
amended. Under this Agreement, each Fund pays MFS an administrative fee of up to
0.015% per annum of the Fund's average daily net assets. This fee reimburses MFS
for a portion of the costs it incurs to provide such services.
 
DISTRIBUTOR -- MFD, a wholly owned subsidiary of MFS, is the distributor of the
shares of each Fund and also serves as distributor for each of the other MFS
Funds.
 
SHAREHOLDER SERVICING AGENT -- MFS Service Center, Inc. ("Shareholder Servicing
Agent"), a wholly owned subsidiary of MFS, performs transfer agency, certain
dividend disbursing agency and other services for the Funds.
 
   
6.  YEAR 2000 ISSUES
    
 
   
Each Fund could be adversely affected if the computer systems used by MFS, each
Fund's other service providers or the companies in which each Fund invests do
not properly process date-related information from and after January 1, 2000
(the "Year 2000 Issue"). MFS recognizes the importance of the Year 2000 Issue
and, to address Year 2000 compliance, created a Year 2000 Program Management
Office in 1996, which is separately funded, has a specialized staff and reports
directly to MFS senior management. The Office, with the help of external
consultants, is responsible for ascertaining that all internal systems, data
feeds and third party applications are Year 2000 compliant. While MFS is
confident that all MFS systems will be Year 2000 compliant before the turn of
the century, there are significant systems interdependencies in the domestic and
foreign markets for securities, the business environments in which companies
held by the Fund operate and in MFS' own business environment. MFS has been
actively working with each Fund's other service providers to identify and
respond to potential problems in an effort to ensure Year 2000 compliance or
develop contingency plans. Year 2000 compliance is also one of the factors
considered by MFS in its ongoing assessment of companies in which each Fund
invests. There can be no assurance, however, that these steps will be sufficient
to avoid any adverse impact on the Funds.
    
 
   
7.  INFORMATION CONCERNING SHARES OF THE FUNDS
    
 
PURCHASES
 
Shares of each Fund may be purchased without a sales charge at net asset value.
It is anticipated that the net asset value of $1.00 per share will remain
constant and the Trust will employ specific investment policies and procedures
to accomplish this result, although no assurance can be
 
                                       11
<PAGE>   20
 
given that it will be able to do so on a continuing basis (see "Net Income and
Distributions"). Except as described below, the minimum initial investment in
either Fund is $1,000 per account and the minimum additional investment is $50
per account. While there is no sales charge, brokers may charge for their
services in connection with a purchase of shares.
 
Accounts being established for monthly automatic investments and under payroll
savings programs and tax-deferred retirement programs (other than Individual
Retirement Accounts ("IRAs")) involving the submission of investments by means
of group remittal statements are subject to a $50 minimum on initial and
additional investments per account. The minimum initial investment for IRAs is
$250 per account and the minimum additional investment is $50 per account. There
are also other limited exceptions to these minimums for certain tax-deferred
programs. The minimum initial investment per account for participation in the
Automatic Transfer Plan is $5,000. Any minimums may be changed at any time at
the discretion of the Trust.
 
All investments in each Fund are credited to the shareholder's account in the
form of full and fractional shares of that Fund at the rate of one share for
each dollar invested. The Trust does not issue share certificates for either
Fund, but the Shareholder Servicing Agent maintains an account for each
shareholder and mails to each shareholder a confirmation of purchases or sales
in his account.
 
Each shareholder may purchase additional shares of any MFS Fund by telephoning
the Shareholder Servicing Agent toll-free at (800) 225-2606. The minimum
purchase amount is $50 and the maximum purchase amount is $100,000. Shareholders
wishing to avail themselves of this telephone purchase privilege must so elect
on their Account Application and designate thereon a bank and account number
from which purchases will be made. If a telephone purchase request is received
by the Shareholder Servicing Agent on any business day prior to the close of
regular trading on the Exchange (generally, 4:00 p.m., Eastern time), the
purchase will occur at the closing net asset value of the shares purchased on
that day. The Shareholder Servicing Agent may be liable for any losses resulting
from unauthorized telephone transactions if it does not follow reasonable
procedures designed to verify the identity of the caller. The Shareholder
Servicing Agent will request personal or other information from the caller, and
will normally also record calls. Shareholders should verify the accuracy of
confirmation statements immediately after their receipt.
 
   
RIGHT TO REJECT PURCHASE ORDERS/MARKET TIMING.  Purchases and exchanges should
be made for investment purposes only. Each Fund and MFD reserve the right to
reject or restrict any specific purchase or exchange request. Because an
exchange request involves both a request to redeem shares of one fund and to
purchase shares of another fund, each Fund considers the underlying redemption
request conditioned upon the acceptance of the underlying purchase request.
Therefore, in the event that a Fund or MFD rejects an exchange request, neither
the redemption nor the purchase side of the exchange will be processed.
    
 
   
The MFS Family of Funds is not designed for professional market timing
organizations or other entities using programmed or frequent exchanges. The MFS
Family of Funds defines a "market timer" as an individual or organization acting
on behalf of one or more individuals, if (i) the individual or organization
makes six or more exchange requests among the MFS Family of Funds or three or
more exchange requests out of any of the MFS high yield bond funds or MFS
municipal bond funds per calendar year and (ii) any one of such exchange
requests represents
    
 
                                       12
<PAGE>   21
 
   
shares equal in value to $1 million or more. Accounts under common ownership or
control, including accounts administered by market timers, will be aggregated
for purposes of this definition.
    
 
   
As noted above, each Fund and MFD reserves the right to reject or restrict any
specific purchase and exchange request and, in addition, may impose specific
limitations with respect to market timers, including (i) delaying for up to
seven days the purchase side of an exchange request by market timers, (ii)
rejecting or otherwise restricting purchase or exchange requests by market
timers; and (iii) permitting exchanges by market timers only into certain MFS
Funds.
    
 
OPENING AN ACCOUNT:
 
  BY MAIL
 
Payment may be made by check or other negotiable bank draft payable to the order
of MFS Service Center, Inc., and mailed with the Account Application Form to the
Shareholder Servicing Agent:
 
  MFS Service Center, Inc.
  P.O. Box 2281
  Boston, Massachusetts 02107-9906.
 
The Fund to be purchased should be designated on the Account Application Form.

  BY WIRE
 
Payment may be wired in federal funds to the Custodian of the Trust as follows:
State Street Bank and Trust Company, Boston, MA, Attn: Mutual Funds Division,
For the Account of: [Shareholder's name], Re: MFS Money Market Fund (4423-744-4)
or MFS Government Money Market Fund (4423-710-5) and Wire Number: [assigned by
telephone]. Information on how to wire federal funds is available at any
national bank or any state bank which is a member of the Federal Reserve System.
A SHAREHOLDER CHOOSING THIS METHOD FOR AN INVESTMENT SHOULD FIRST TELEPHONE THE
SHAREHOLDER SERVICING AGENT TOLL-FREE AT (800) 225-2606 TO ADVISE OF HIS
INTENDED ACTION AND THE FUND TO BE PURCHASED, AND TO OBTAIN A WIRE ORDER NUMBER.
 
EXCHANGES
 
Shares of either Fund which are acquired through direct purchase for which
payment has been received by the Trust (i.e., an established account) may be
exchanged at net asset value for shares of the other Fund without the imposition
of a sales charge. Shares of either Fund may be exchanged for Class A shares of
any of the other MFS Funds at net asset value plus their normal sales charge (if
available for sale). However, this charge will not apply to: (i) shares
exchanged from either Fund acquired by an exchange from any other MFS Fund; (ii)
shares exchanged from either Fund acquired by automatic investment of dividends
from any other MFS Fund paid after June 1, 1992; or (iii) shares exchanged from
either Fund where the shares being exchanged would have, at the time of
purchase, been eligible for purchase at net asset value without the imposition
of a sales charge had the shareholder made a direct investment in the MFS Fund
into which the exchange is being made. In addition, shares of the Money Market
Fund previously acquired through an exchange from Class C shares or Class I
shares of a MFS Fund may be exchanged for Class C shares or Class I shares,
respectively, of any of the other MFS Funds at net asset value (if available for
sale and if the purchaser is eligible to purchase that class of
 
                                       13
<PAGE>   22
 
shares). In the event that shares of either Fund are acquired through an
exchange from shares of any other MFS Fund bearing a CDSC, the CDSC will be
unaffected by the exchange and the holding period for purposes of calculating
the CDSC will carry over to the acquired shares. Exchanges will be made only
after instructions in writing or by telephone (an "Exchange Request") are
received for an established account by the Shareholder Servicing Agent in proper
form (i.e., if in writing -- signed by the record owner(s) exactly as the shares
are registered; if by telephone -- proper account identification is given by the
dealer or shareholder of record), and each exchange must involve shares having
an aggregate value of at least $1,000 ($50 in the case of retirement plan
participants whose sponsoring organizations subscribe to the MFS FUNDamental
401(k) Plan or another similar 401(k) recordkeeping system made available by the
Shareholder Servicing Agent) or all the shares in the account. If an Exchange
Request is received by the Shareholder Servicing Agent in writing or by
telephone on any business day prior to the close of regular trading on the New
York Stock Exchange (the "Exchange"), the exchange will usually occur that day
if all the requirements set forth above have been complied with at that time. No
more than five exchanges may be made in any one Exchange Request by telephone.
Exchanges by telephone are automatically available to most non-retirement plan
accounts and certain retirement plan accounts. For further information regarding
exchanges by telephone see "Redemptions By Telephone." The exchange privilege
(or any aspect of it) may be changed or discontinued and is subject to certain
limitations, including certain restrictions on purchases by market timers.
 
REDEMPTIONS
 
A shareholder in either Fund may withdraw all or any portion of the amount in
his account on any date on which the Trust is open for business by redeeming
shares at their net asset value, normally $1.00 per share. The redemption
proceeds will be reduced by any applicable CDSC. For the convenience of
shareholders and to enable them to continue earning daily dividends for as long
as possible, the Trust has arranged for several different procedures for
redemption. The proceeds of a redemption will normally be available within one
business day or, in any event, within seven days (except, in certain cases,
redemptions of shares purchased by check -- see below).
 
Shares of either Fund which are purchased directly (i.e., are not exchanged from
any other MFS Fund) will not bear a CDSC upon redemption. However, as noted
above under "Exchanges," in the event that shares of either Fund are acquired
through an exchange from shares of any other MFS Fund bearing a CDSC, the CDSC
will be unaffected by the exchange and the holding period for purposes of
calculating the CDSC will carry over to the acquired shares. The maximum CDSC
applicable to shares of other MFS Funds which are eligible for exchange into
either Fund is 1%, and this CDSC expires after shares have been held for
approximately one year. Any applicable CDSC is assessed against the lesser of
the value of the shares redeemed (exclusive of reinvested dividends and capital
gain distributions) or the total cost of such shares. For further information on
the CDSC, see the "Redemption and Repurchases" section of the prospectus of the
MFS Fund from which the exchange is made.
 
A.  BY CHECK -- State Street Bank and Trust Company (the "Bank") will provide
each shareholder, upon request, with forms of checks drawn on the Bank. Checks
may be payable in any amount not less than $500. Shareholders wishing to avail
themselves of this redemption by
                                       14
<PAGE>   23
 
check privilege must so elect on their Account Application Form and must execute
signature cards (for additional information, see the reverse side of the
signature card) with signature guaranteed in the manner set forth under the
caption "Signature Guarantee" below. Additional documentation will be required
from corporations, partnerships, fiduciaries or other institutional investors.
All checks must be signed by the shareholder(s) of record exactly as the account
is registered before the Bank will honor them. The shareholders of joint
accounts may authorize each shareholder to redeem by check. Shareholders who
purchase shares by check (including certified checks or cashiers checks) may
write checks against those shares only after they have been on the Fund's books
for 15 days. When such a check is presented to the Bank for payment, a
sufficient number of full and fractional shares will be redeemed to cover the
amount of the check, any applicable CDSC and the amount of any income tax
required to be withheld. If the amount of the check, plus any applicable CDSC
and the amount of any income tax required to be withheld is greater than the
value of the shares held in the shareholders' account, the check will be
returned unpaid, and the shareholder may be subject to extra charges. The check
may not draw on month-to-date dividends which have been declared but not
distributed. To avoid dishonor of checks due to fluctuations in the value of
each account, shareholders are advised against closing accounts by means of a
check. Checks should not be used to close a Fund account because when the check
is written, the shareholder will not know the exact total value of the account
on the day the check clears. There is presently no charge to the shareholder for
the maintenance of this special checking account or for the clearance of any
checks, but the Trust reserves the right to impose such charges or to modify or
terminate the redemption by check privilege at any time.
 
B.  BY MAIL -- Each shareholder has the right to redeem all or any portion of
the shares in his account by mailing or delivering to the Shareholder Servicing
Agent (see back cover for address) a stock power, together with a written
request for redemption, or a letter of instructions, all in "good order" for
transfer. "Good order" generally means that a stock power, written request for
redemption, or letter of instruction must be endorsed by the record owner(s)
exactly as the shares are registered and the signature(s) must be guaranteed in
the manner set forth below under the caption "Signature Guarantee" below. In
addition, in some cases, "good order" may require the furnishing of additional
documents.
 
C.  BY TELEPHONE -- Each shareholder may redeem an amount from his account by
telephoning the Shareholder Servicing Agent toll-free at (800) 225-2606.
Shareholders wishing to avail themselves of this telephone redemption privilege
must so elect on their Account Application Form, designate thereon a commercial
bank and account number to receive the proceeds of such redemption, and sign the
Account Application Form with the signature(s) guaranteed in the manner set
forth below under the caption "Signature Guarantee" below. The proceeds of such
a redemption are mailed by check to the designated account, without charge. As a
special service, investors may arrange to have proceeds in excess of $1,000
wired in federal funds to the designated account. Subject to the conditions
described in this section, proceeds of a redemption are normally mailed or wired
on the next business day following the date of receipt of the order for
redemption. During times of drastic economic or market changes, a shareholder
may experience delays in reaching the above telephone number. This redemption
privilege (or any aspect of it) may be changed or discontinued without notice to
shareholders. The Shareholder Servicing Agent will not be responsible for any
losses resulting from unauthorized telephone
 
                                       15
<PAGE>   24
 
transactions if it follows reasonable procedures designed to verify the identity
of the caller. The Shareholder Servicing Agent will request personal or other
information from the caller, and will normally also record calls. Shareholders
should verify the accuracy of confirmation statements immediately after their
receipt.
 
   
D.  GENERAL -- When a shareholder withdraws an amount from his account, the
shareholder is deemed to have tendered for redemption a sufficient number of
full and fractional shares in his account to cover the amount withdrawn. For
shares purchased, or received in exchange for shares purchased, by check
(including certified checks or cashier's checks), payment of redemption proceeds
may be delayed for up to 15 days from the purchase date in an effort to insure
that such check has cleared.
    
 
Due to the relatively high cost of maintaining small accounts, each Fund
reserves the right to redeem shares in any account for their then-current value
(which will be promptly paid to the shareholder) if at any time the total
investment in such account drops below $500 because of redemptions or exchanges,
except in the case of accounts established for monthly automatic investments and
certain payroll savings programs and tax-deferred retirement plans, for which
the minimum investment requirement is either $250 or $50. Shareholders will be
notified that the value of their account is less than the minimum investment
requirement and allowed 60 days to make an additional investment before the
redemption is processed.
 
The right of redemption can be suspended and the payment of the redemption
proceeds deferred during any period in which the Exchange is closed or trading
on the Exchange is restricted or to the extent otherwise permitted by the 1940
Act if an emergency exists.
 
The Shareholder Servicing Agent may make certain de minimis exceptions to the
requirements for redemption.
 
IN-KIND DISTRIBUTIONS:  The Trust agrees to redeem shares of the Fund solely in
cash up to the lesser of $250,000 or 1% of the net asset value of the Fund
during any 90-day period for any one shareholder. Each Fund has reserved the
right to pay other redemptions, either totally or partially, by a distribution
in-kind of securities (instead of cash) from such Fund's portfolio. The
securities distributed in such a distribution would be valued at the same amount
as that assigned to them in calculating the net asset value for the shares being
sold. If a shareholder received a distribution in-kind, the shareholder could
incur brokerage or transaction charges when converting the securities to cash.
 
SIGNATURE GUARANTEE:  In order to protect shareholders against fraud, the Trust
requires in certain instances as indicated above that the shareholder's
signature be guaranteed. In these cases the shareholder's signature must be
guaranteed by an eligible bank, broker, dealer, credit union, national
securities exchange, registered securities association, clearing agency or
savings association. Signature guarantees shall be accepted in accordance with
policies established by the Shareholder Servicing Agent.
 
DETERMINATION OF NET ASSET VALUE
 
Securities are valued at amortized cost, which the Trustees have determined in
good faith constitutes fair value for the purposes of complying with the 1940
Act. This valuation method will continue to be used until such time as the
Trustees determine that it does not constitute fair value for such purposes.
Since the Net Income, as defined in the SAI, of each Fund is declared as
 
                                       16
<PAGE>   25
 
a dividend each time the Net Income of that Fund is determined, the net asset
value per share of that Fund (i.e., the value of the net assets of that Fund
divided by the number of shares of that Fund outstanding) remains at $1.00 per
share immediately after each such determination and dividend declaration. Any
increase in the value of a shareholder's investment in either Fund, representing
the reinvestment of dividend income, is reflected by an increase in the number
of shares of that Fund in his account.
 
It is expected that each Fund will have a positive Net Income at the time of
each determination thereof. If for any reason the Net Income of either Fund
determined at any time is a negative amount, that Fund will first offset the
negative amount with respect to each shareholder account in that Fund from the
dividends declared during the month with respect to such account. Then, to the
extent necessary, such Fund will reduce the number of its outstanding shares by
treating each of its shareholders as having contributed to its capital that
number of full and fractional shares in the account of such shareholder which
represents his proportion of such excess. Each shareholder of that Fund will be
deemed to have agreed to such contribution in these circumstances by his
investment in that Fund. This procedure will permit the net asset value per
share of each Fund to be maintained at a constant $1.00 per share.
 
DISTRIBUTIONS
 
The Net Income of each Fund is determined each day during which the Exchange is
open for trading. This determination is made once during each such day as of the
close of regular trading. All the Net Income of each Fund so determined is
declared in shares of the respective Fund at the time of such determination.
Shares purchased become entitled to dividends declared as of the first day
following the date of investment. Dividends are generally distributed on the
last business day of each month in the form of additional shares of the
respective Fund at the rate of one share (and fraction thereof) for each one
dollar (and fraction thereof) of dividend income attributable to that Fund, or,
at the election of the shareholder, in cash; except that if a shareholder
redeems the entire amount in his account with that Fund at any time during the
month, all dividends declared on that series during the month through the date
of redemption will be paid to him at the same time as the proceeds from the
redemption of his shares. The Fund may make one or more distributions during the
calendar year to its shareholders from any long-term capital gains, and may also
make one or more distributions during the calendar year to its shareholders from
short-term capital gains.
 
TAX STATUS
 
   
Each Fund is treated as an entity separate from the other series of the Trust
for federal income tax purposes. In order to minimize the taxes each Fund would
otherwise be required to pay, each Fund intends to qualify each year as a
"regulated investment company" under Subchapter M of the Internal Revenue Code
of 1986, as amended (the "Code"). Because each Fund intends to distribute all of
its net investment income and net realized capital gains to its shareholders in
accordance with the timing requirements set out in the Code, it is not expected
that the Funds will be required to pay any entity level federal income or excise
taxes, although foreign source income earned by the MFS Money Market Fund may be
subject to foreign withholding taxes.
    
 
   
Shareholders of each Fund normally will have to pay federal income taxes and any
state or local taxes on the dividends and capital gain distributions they
receive from the Fund, whether paid in
    
 
                                       17
<PAGE>   26
 
   
cash or reinvested in additional shares. The Funds expect that none of their
distributions will be eligible for the dividends received deduction for
corporations. Shareholders may not have to pay state or local taxes on dividends
derived from interest on U.S. Government obligations. Investors should consult
with their tax advisers in this regard. Shortly after the end of each calendar
year, each shareholder will be sent a statement setting forth the federal income
tax status of all dividends and distributions for that year, including the
portion taxable as ordinary income, the portion, if any, taxable as long-term
capital gain (as well as the rate category or categories under which such gain
is taxable), the portion, if any, representing a return of capital (which is
generally free of current taxes but which results in a basis reduction), the
portion representing interest on U.S. Government obligations, and the amount, if
any, of federal income tax withheld.
    
 
Each Fund intends to withhold U.S. federal income tax at the rate of 30% (or any
lower rate permitted under an applicable treaty) on taxable dividends and other
payments that are subject to such withholding and that are made to persons who
are neither citizens nor residents of the U.S. Each Fund is also required in
certain circumstances to apply backup withholding at the rate of 31% on taxable
dividends paid to any shareholder (including a shareholder who is neither a
citizen nor a resident of the U.S.) who does not furnish to the Fund certain
information and certifications or who is otherwise subject to backup
withholding. Backup withholding will not, however, be applied to payments that
have been subject to 30% withholding.
 
Prospective investors should read the Funds' Account Application for additional
information regarding backup withholding of federal income tax and should
consult their own tax advisers as to the tax consequences to them of an
investment in a Fund.
 
DESCRIPTION OF SHARES, VOTING RIGHTS AND LIABILITIES
 
Each Fund has only one class of shares, entitled Shares of Beneficial Interest
(without par value). The Trust presently has four series of shares and has
reserved the right to create and issue additional series of shares. Each share
of a series represents an equal proportionate interest in that series with each
other share of that series. The shares of each series participate equally in the
earnings, dividends and assets of the particular series. Shares have no
pre-emptive or conversion rights. Shares when issued are fully paid and
non-assessable. Shareholders are entitled to one vote for each share held.
Shares of each series vote separately to approve investment advisory agreements
or changes in investment objective or restrictions, but shares of all series
vote together in the election or selection of Trustees and accountants.
Shareholders of each series would be entitled to share pro rata in the net
assets of their respective portfolio available for distribution to shareholders
upon liquidation of the Trust or that series.
 
The Trust is an entity of the type commonly known as a "Massachusetts business
trust." Under Massachusetts law, shareholders of such a trust may, under certain
circumstances, be held personally liable as partners for its obligations.
However, the risk of a shareholder incurring financial loss on account of
shareholder liability is limited to circumstances in which both inadequate
insurance (e.g., fidelity bonding and errors and omissions insurance) existed
and the Trust itself was unable to meet its obligations.
 
PERFORMANCE INFORMATION
 
From time to time, each Fund may advertise its yield and effective yield. Both
yield and effective yield are based on historical earnings and are not intended
to indicate future performance. The
 
                                       18
<PAGE>   27
 
yield of a Fund refers to the income generated by an investment in that series
over a seven-day period (which period will be stated in the advertisement). This
income is then annualized; that is, the amount of income generated by the
investment during that week is assumed to be generated each week over a 52-week
period and is shown as a percentage of the investment. The effective yield is
calculated similarly but, when annualized, the income earned by an investment in
a Fund is assumed to be reinvested. The effective yield will be slightly higher
than the yield because of the compounding effect of this assumed reinvestment.
 
The yield of each Fund will vary based on the type, quality, and maturities of
the securities held in the portfolio of the particular series, fluctuations in
short-term interest rates and changes in the Trust's expenses. For a discussion
of the manner in which each Fund will calculate its yield, see the SAI. In
addition to information provided in shareholder reports, the Fund may, in its
discretion, from time to time, make a list of all or a portion of its holdings
available to investors upon request.
 
   
PROVISION OF ANNUAL AND SEMIANNUAL REPORTS
    
 
   
To avoid sending duplicate copies of materials to households, effective
September 15, 1998, only one copy of each Fund's annual and semiannual report
may be mailed to shareholders having the same residential address on the Fund's
records. However, any shareholder may call the Shareholder Servicing Agent at
1-800-225-2606 to request that copies of such reports be sent personally to that
shareholder.
    
 
   
8.  SHAREHOLDER SERVICES
    
 
Shareholders with questions concerning the shareholder services described below
or concerning other aspects of the Funds, should contact the Shareholder
Servicing Agent (see back cover for address and phone number). The Shareholder
Servicing Agent, which is a wholly owned subsidiary of the Adviser, performs
transfer agency, certain dividend disbursing agency and other services for the
Trust.
 
ACCOUNT AND CONFIRMATION STATEMENTS -- Each shareholder will receive a
confirmation statement showing the activity in his account. At the end of each
calendar year, each shareholder will receive income tax information regarding
distributions made by the Fund for that year and the amount, if any, of federal
income tax withheld.
 
DISTRIBUTION OPTIONS -- The following options are available to all accounts
(except Systematic Withdrawal Plan accounts described below) and may be changed
as often as desired by notifying the Shareholder Servicing Agent:
 
         -- Dividends reinvested in additional shares (this option will be
            assigned if no other option is specified); or
 
         -- Dividends in cash.
 
Dividends in amounts less than $10 will automatically be reinvested in
additional shares of the applicable Fund. If a shareholder has elected to
receive dividends in cash, and the postal or other delivery service is unable to
deliver checks to the shareholder's address of record, or the shareholder does
not respond to mailings from the Shareholder Servicing Agent with regard to
uncashed distribution checks, such shareholder's distribution option will
automatically be converted to having all dividends reinvested in additional
shares. Any request to change a
                                       19
<PAGE>   28
 
distribution option must be received by the Shareholder Servicing Agent by the
record date for a dividend in order to be effective for that dividend. No
interest will accrue on amounts represented by uncashed distribution or
redemption checks.
 
INVESTMENT OR WITHDRAWAL PROGRAMS -- For the convenience of shareholders, the
Funds make available the following programs designed to enable shareholders to
add to their investment in an account with the Funds or withdraw from it with a
minimum of paper work. The programs involve no extra charge to shareholders
(other than a sales charge in the case of certain share purchases) and may be
changed or discontinued at any time by a shareholder or the Fund.
 
    DISTRIBUTION INVESTMENT PROGRAM:  Dividend distributions made by either Fund
may be automatically invested in shares of one of the other MFS Funds, if shares
of the particular fund are available for sale.
 
    SYSTEMATIC WITHDRAWAL PLAN:  A shareholder may direct the Shareholder
Servicing Agent to send him (or anyone he designates) regular periodic payments
based upon the value of his account. Each payment under a Systematic Withdrawal
Plan must be at least $100, except in certain limited circumstances.
 
DOLLAR COST AVERAGING PROGRAMS
 
    AUTOMATIC INVESTMENT PLAN:  Cash investments of $50 or more may be made
through a shareholder's checking account on any day of the month. If the
shareholder does not specify a date, the investment will automatically occur on
the first business day of the month. Required forms are available from the
Shareholder Servicing Agent or investment dealers.
 
    AUTOMATIC EXCHANGE PLAN:  Shareholders having account balances of at least
$5,000 in any MFS Fund, may exchange their shares for the same class of shares
of other MFS Funds under the Automatic Exchange Plan. The Automatic Exchange
Plan provides for automatic monthly or quarterly exchanges of funds from the
shareholder's account in an MFS Fund for investment in the same class of shares
of other MFS Funds selected by the shareholder. Under the Automatic Exchange
Plan, exchanges of at least $50 each may be made to up to six different funds. A
shareholder should consider the differences in objectives and policies of a fund
and review its prospectus before electing to exchange money into such fund
through the Automatic Exchange Plan. No transaction fee is imposed in connection
with exchange transactions under the Automatic Exchange Plan. HOWEVER, EXCHANGES
FROM EITHER OF THE MONEY MARKET FUNDS WILL BE SUBJECT TO ANY APPLICABLE SALES
CHARGE. For Federal and (generally) state income tax purposes, an exchange is
treated as a sale of the shares exchanged and, therefore, could result in a
capital gain or loss to the shareholder making the exchange. See the SAI for
further information concerning the Automatic Exchange Plan. Investors should
consult their tax advisers for information regarding the potential capital gain
and loss consequences of transactions under the Automatic Exchange Plan.
 
TAX-DEFERRED RETIREMENT PLANS -- Shares of either Fund may be purchased by all
types of tax-deferred retirement plans, including IRAs; SEP-IRAs; 401(k) plans;
403(b) plans and other qualified pension and profit-sharing plans. Investors
should consult with their tax advisers before establishing any of the
tax-deferred retirement plans described above.
 
                                       20
<PAGE>   29
 
                            ------------------------
 
   
The Fund's SAI, dated January 1, 1999, contains more detailed information about
the Funds, including information related to (i) the Funds' investment
objectives, policies and restrictions, (ii) Trustees, officers and investment
adviser, (iii) portfolio transactions, (iv) the Funds' shares, including rights
and liabilities of shareholders, (v) the method used to calculate the yield and
effective yield of each Fund, and (vi) various services and privileges provided
by the Funds for the benefit of their shareholders.
    
 
                                       21
<PAGE>   30
 
                                   APPENDIX A
 
DESCRIPTION OF CERTAIN FUND INVESTMENTS:
 
U.S. GOVERNMENT OBLIGATIONS -- are issued by the U.S. Treasury and include
bills, certificates of indebtedness, notes and bonds. Agencies and
instrumentalities of the U.S. Government are established under the authority of
an act of Congress and include, but are not limited to, the Government National
Mortgage Association ("GNMA"), the Tennessee Valley Authority, the Bank for
Cooperatives, the Farmers Home Administration, Federal Home Loan Banks ("FHLB"),
Federal Intermediate Credit Banks, Federal Land Banks, and the Federal National
Mortgage Association ("FNMA").
 
REPURCHASE AGREEMENTS -- may be entered into by each Fund in order to earn
additional income on available cash or as a temporary defensive measure. Under a
repurchase agreement, the Fund acquires securities subject to the seller's
agreement to repurchase at a specified time and price. If the seller becomes
subject to a proceeding under the bankruptcy laws or its assets are otherwise
subject to a stay order, the Fund's right to liquidate the securities may be
restricted (during which time the value of the securities could decline). As
discussed in the SAI, the Trust has adopted certain procedures intended to
minimize risk.
 
CERTIFICATES OF DEPOSIT -- are certificates issued against funds deposited in a
bank (including eligible foreign branches of U.S. banks), are for a definite
period of time, earn a specified rate of return, and are normally negotiable.
 
BANKERS' ACCEPTANCES -- are short-term credit instruments used to finance the
import, export, transfer or storage of goods. They are termed "accepted" when a
bank guarantees their payment at maturity.
 
COMMERCIAL PAPER -- refers to promissory notes issued by corporations in order
to finance their short-term credit needs.
 
CORPORATE OBLIGATIONS -- include bonds and notes issued by corporations in order
to finance long-term credit needs. The MFS Money Market Fund will invest only in
corporate obligations which have a maturity when purchased of 13 months or less.
 
                                       A-1
<PAGE>   31
 
Investment Adviser
Massachusetts Financial
Services Company
500 Boylston Street
Boston, MA 02116
(617) 954-5000

Distributor
MFS Fund Distributors, Inc.
500 Boylston Street
Boston, MA 02116
(617) 954-5000

Custodian and Dividend
Disbursing Agent
State Street Bank and Trust Company
225 Franklin Street
Boston, MA 02110
 
Shareholder Servicing Agent
MFS Service Center, Inc.
500 Boylston Street
Boston, MA 02116
Toll-free: (800) 225-2606

Mailing Address:
P.O. Box 2281
Boston, MA 02107-9906
 
Independent Auditors
Deloitte & Touche LLP
125 Summer Street
Boston, MA 02110
<PAGE>   32
 
[MFS LOGO]
MFS(R) MONEY MARKET FUND
MFS(R) GOVERNMENT MONEY
MARKET FUND
 
(Members of the MFS Family of Funds(R))
                                             STATEMENT OF
                                             ADDITIONAL INFORMATION
 
   
                                             January 1, 1999
    
 
- --------------------------------------------------------------------------------
 
<TABLE>
<CAPTION>
                                                                     Page
                                                                     ----
<C>    <S>                                                           <C>
   1.  Definitions.................................................     2
   2.  Investment Objective, Policies and Restrictions.............     2
   3.  Management of the Funds.....................................     3
       Trustees....................................................     3
       Officers....................................................     4
       Trustee Compensation Table..................................     5
       Investment Adviser..........................................     7
       Administrator...............................................     8
       Distributor.................................................     8
       Custodian...................................................     8
       Shareholder Servicing Agent.................................     8
   4.  Portfolio Transactions and Brokerage Commissions............     8
   5.  Shareholder Services........................................     9
       Investment and Withdrawal Programs..........................     9
       Exchange Privilege..........................................    10
       Tax-Deferred Retirement Plans...............................    11
   6.  Tax Status..................................................    11
   7.  Description of Shares, Voting Rights and Liabilities........    12
   8.  Net Income and Distributions................................    12
   9.  Performance Information.....................................    13
  10.  Independent Auditors and Financial Statements...............    14
       Appendix A (Commercial Paper and Bond Ratings)..............   A-1
</TABLE>
 
MFS MONEY MARKET FUND
MFS GOVERNMENT MONEY MARKET FUND
Series of MFS Series Trust IV
500 Boylston Street, Boston, Massachusetts 02116
(617) 954-5000
 
   
This Statement of Additional Information, as amended or supplemented from time
to time (the "SAI"), sets forth information which may be of interest to
investors but which is not necessarily included in the Funds' Prospectus, dated
January 1, 1999. This SAI should be read in conjunction with the Prospectus, a
copy of which may be obtained without charge by contacting the Shareholder
Servicing Agent (see last page for address and phone number).
    
 
THIS SAI IS NOT A PROSPECTUS AND IS AUTHORIZED FOR DISTRIBUTION TO PROSPECTIVE
INVESTORS ONLY IF PRECEDED OR ACCOMPANIED BY A CURRENT PROSPECTUS.
<PAGE>   33
 
1. DEFINITIONS
 
   
<TABLE>
<S>                        <C>   <C>
"Trust"                    --    MFS Series Trust IV, a
                                 Massachusetts business
                                 trust. The Trust was known
                                 as Massachusetts Cash
                                 Management Trust prior to
                                 August 27, 1993.
"Money Market Funds"       --    The MFS Money Market Fund
  or "Funds"                     and the MFS Government
                                 Money Market Fund, both of
                                 which are diversified
                                 series of the Trust.
"MFS" or the "Adviser"     --    Massachusetts Financial
                                 Services Company, a
                                 Delaware corporation.
"Prospectus"               --    The Prospectus of the
                                 Funds, dated January 1,
                                 1999, as amended or
                                 supplemented from time to
                                 time.
</TABLE>
    
 
2. INVESTMENT OBJECTIVE, POLICIES AND RESTRICTIONS
 
INVESTMENT OBJECTIVE. The investment objective of each Money Market Fund is to
seek as high a level of current income as is considered consistent with the
preservation of capital and liquidity. The investment objective of a Fund will
not be changed without first obtaining shareholder approval from the
shareholders of that Fund. Any investment involves risk and there can be no
assurance that either Money Market Fund will achieve its investment objective.
 
INVESTMENT POLICIES. The investment policies of the Funds are described in the
Prospectus. In addition, certain of the Funds' investment policies are described
in greater detail below.
 
REPURCHASE AGREEMENTS: Each Fund may enter into repurchase agreements with
sellers who are member firms (or a subsidiary thereof) of the New York Stock
Exchange (the "Exchange") or members of the Federal Reserve System, recognized
primary U.S. Government securities dealers or institutions which the Adviser has
determined to be of comparable creditworthiness. The securities that a Fund
purchases and holds through its agent are U.S. Government securities, the values
of which are equal to or greater than the repurchase price agreed to be paid by
the seller. The repurchase price may be higher than the purchase price, the
difference being income to the Fund, or the purchase and repurchase prices may
be the same, with interest at a standard rate due to the Fund together with the
repurchase price on repurchase. In either case, the income to the Fund is
unrelated to the interest rate on the U.S. Government securities.
 
The repurchase agreement provides that in the event the seller fails to pay the
price agreed upon on the agreed upon delivery date or upon demand, as the case
may be, the applicable Fund will have the right to liquidate the securities. If,
at the time the Fund is contractually entitled to exercise its right to
liquidate the securities, the seller is subject to a proceeding under the
bankruptcy laws or its assets are otherwise subject to a stay order, the series'
exercise of its right to liquidate the securities may be delayed and result in
certain losses and costs to the Fund. The Trust has adopted and follows
procedures which are intended to minimize the risk of repurchase agreements. For
example, a Fund only enters into repurchase agreements after the Adviser has
determined that the seller is creditworthy, and the Adviser monitors the
seller's creditworthiness on an ongoing basis. Moreover, under such agreements,
the value of the securities (which are marked to market every business day) is
required to be greater than the repurchase price, and the Fund has the right to
make margin calls at any time if the value of the securities falls below the
agreed upon margin.
 
INVESTMENT RESTRICTIONS. The Trust has adopted the following investment
restrictions which apply to each of the Funds and which cannot be changed with
respect to either Fund without the approval of the holders of a majority of the
shares of that Fund (which, as used in this SAI, means the lesser of (i) more
than 50% of the outstanding shares of that Fund, or (ii) 67% or more of the
outstanding shares of that Fund present at a meeting if holders of more than 50%
of the outstanding shares of that Fund are represented at such meeting in person
or by proxy):
 
Neither Fund may:
 
    (1) Borrow money or pledge, mortgage or hypothecate its assets, except as a
  temporary measure in an amount not to exceed one-third of its total assets
  (taken at current value) to facilitate redemptions (a loan limitation in
  excess of 5% is generally associated with a leveraged fund, but, since neither
  Fund anticipates paying interest on borrowed money at rates comparable to its
  yield, neither Fund has any intention of attempting to increase its net income
  by means of borrowing. Each Fund will borrow money only to accommodate
  requests for the repurchase of its shares while effecting an orderly
  liquidation of portfolio securities); and except that either Fund may enter
  into repurchase agreements (see description above);
 
    (2) Underwrite securities except insofar as the Trust may technically be
  deemed an underwriter under the Securities Act of 1933 in selling a portfolio
  security;
 
    (3) Purchase voting securities of any issuer or purchase the securities of
  any issuer if, as a result thereof, more than 25% of that Fund's total assets
  (taken at current value) would be concentrated in any one industry; provided,
  however, that (a) there is no limitation in respect to investments in
  obligations issued or guaranteed by the U.S. Government or its agencies or
  instrumentalities, and (b) each Fund may invest up to 75% of its assets in all
  finance companies as a group, all banks and bank holding companies as a group
  and all utility companies as a group when in the opinion of management yield
  differentials and money market conditions suggest and when cash is available
  for such investment and instruments are available for purchase which fulfill
  the Fund's objective in terms of quality and marketability;
 
    (4) Purchase or retain real estate (including limited partnership interests
  but excluding securities of companies which deal in real estate or interests
  therein), mineral leases, commodities or commodity contracts;
 
                                        2
<PAGE>   34
 
    (5) Make loans to other persons except by the purchase of obligations in
  which that Fund is authorized to invest and by entering into repurchase
  agreements (see description above); not more than 10% of the total assets of
  either Fund (taken at current value) will be subject to repurchase agreements
  maturing in more than seven days;
 
    (6) Purchase the securities of any issuer if such purchase, at the time
  thereof, would cause more than 5% of that Fund's total assets (taken at
  current value) to be invested in the securities of such issuer, other than
  securities issued or guaranteed by the U.S. Government or its agencies or
  instrumentalities;
 
    (7) Purchase securities of any issuer (other than securities issued or
  guaranteed by the U.S. Government or its agencies or instrumentalities) if
  such purchase at the time thereof would cause that Fund to hold more than 10%
  of any class of securities of such issuer; for this purpose all debt
  obligations of an issuer maturing in less than one year shall be deemed a
  single class;
 
    (8) Invest in companies for the purpose of exercising control or management;
 
    (9) Purchase securities issued by any registered investment company except
  by purchase in the open market where no commission or profit to a sponsor or
  dealer results from such purchase other than the customary broker's
  commission, or except when such purchase, though not made in the open market,
  is part of a plan of merger or consolidation; provided, however, that neither
  Fund will purchase the securities of any registered investment company if such
  purchase at the time thereof would cause more than 10% of the total assets of
  that Fund (taken at current value) to be invested in the securities of such
  issuers; and provided, further, that neither Fund will purchase securities
  issued by any open-end investment company;
 
    (10) Invest more than 5% of its total assets (taken at current value) in
  companies which, including predecessors, have a record of less than three
  years' continuous operation;
 
    (11) Purchase or retain securities of any issuer any of whose officers,
  directors, or security-holders is a Trustee or officer of the Trust, or is an
  officer or Director of the Adviser, if or so long as one or more of such
  persons owns beneficially more than 1/2 of 1% of any class of securities,
  taken at market value, of such issuer, and such persons owning more than 1/2
  of 1% of such securities together own beneficially more than 5% of any class
  of securities, taken at market value;
 
    (12) Purchase securities on margin except that either Fund may obtain such
  credits as may be necessary for the clearance of purchases and sales of
  securities;
 
    (13) Make short sales of securities;
 
    (14) Write or purchase any put or call option; or
 
    (15) Invest in securities which are restricted as to disposition under
  federal securities laws, or securities with other legal or contractual
  restrictions on resale, except for repurchase agreements.
 
As a matter of non-fundamental policy, neither Fund may invest 25% or more of
the market value of its total assets in securities of issuers in any one
industry.
 
Except with respect to Investment Restriction (1), these investment restrictions
are adhered to at the time of purchase or utilization of assets; a subsequent
change in circumstances will not be considered to result in a violation of
policy.
 
3. MANAGEMENT OF THE FUNDS
 
The Board of Trustees provides broad supervision over the affairs of the Trust.
The Adviser is responsible for the investment management of each Fund, and the
officers of the Trust are responsible for its operations. The Trustees and
officers of the Trust are listed below, together with their principal
occupations during the past five years. (Their titles may have varied during
that period.)
 
TRUSTEES
 
   
RICHARD B. BAILEY* (born 9/14/26)
    
Private Investor; Massachusetts Financial Services Company, former Chairman
  (prior to September 30, 1991); Cambridge Bancorp, Director; Cambridge Trust
  Company, Director
 
PETER G. HARWOOD (born 4/3/26)
Private Investor
Address: 211 Lindsay Pond Road, Concord, Massachusetts
 
J. ATWOOD IVES (born 5/1/36)
   
Eastern Enterprises (diversified services company), Chairman, Trustee and Chief
  Executive Officer
    
Address: 9 Riverside Road, Weston, Massachusetts
 
LAWRENCE T. PERERA (born 6/23/35)
Hemenway & Barnes (attorneys), Partner
Address: 60 State Street, Boston, Massachusetts
 
WILLIAM J. POORVU (born 4/10/35)
Harvard University Graduate School of Business Administration, Adjunct
  Professor; CBL & Associates Properties, Inc. (a real estate investment trust),
  Director; The Baupost Fund (a registered investment company), Vice Chairman
  (since November 1993), Chairman and Trustee (prior to November 1993)
Address: Harvard Business School, Soldiers Field Road, Cambridge, Massachusetts
 
CHARLES W. SCHMIDT (born 3/18/28)
   
Private Investor; International Technology Corporation, Director; Mohawk Paper
  Company, Director
    
Address: 30 Colpitts Road, Weston, Massachusetts
 
ARNOLD D. SCOTT* (born 12/16/42)
Massachusetts Financial Services Company, Senior Executive Vice President,
  Secretary and Director
 
JEFFREY L. SHAMES* (born 6/2/55)
   
Massachusetts Financial Services Company, Chairman and Chief Executive Officer
    
 
                                        3
<PAGE>   35
 
ELAINE R. SMITH (born 4/25/46)
   
Independent Consultant
    
Address: Weston, Massachusetts
 
DAVID B. STONE (born 9/2/27)
North American Management Corp. (investment adviser), Chairman and Director;
  Eastern Enterprises, Trustee
Address: 10 Post Office Square, Suite 300, Boston, Massachusetts
 
OFFICERS
 
W. THOMAS LONDON,* Treasurer (born 3/1/44)
Massachusetts Financial Services Company, Senior Vice President
 
STEPHEN E. CAVAN,* Secretary and Clerk (born 11/6/53)
Massachusetts Financial Services Company, Senior Vice President, General Counsel
  and Assistant Secretary
 
JAMES R. BORDEWICK, JR.,* Assistant Secretary (born 3/6/59)
   
Massachusetts Financial Services Company, Senior Vice President and Associate
  General Counsel
    
 
GEOFFREY L. KURINSKY,* Vice President (born 7/7/53)
Massachusetts Financial Services Company, Senior Vice President
 
JAMES O. YOST,* Assistant Treasurer (born 6/12/60)
Massachusetts Financial Services Company, Vice President
 
MARK E. BRADLEY,* Assistant Treasurer (born 11/23/59)
   
Massachusetts Financial Services Company, Vice President (since March 1997);
  Putnam Investments, Vice President (from September 1994 until March 1997);
  Ernst & Young, Senior Tax Manager (until September 1994)
    
 
   
ELLEN MOYNIHAN,* Assistant Treasurer (born 11/13/57)
    
Massachusetts Financial Services Company, Vice President (since September 1996);
  Deloitte & Touche LLP, Senior Manager (until September 1996)
- ---------------
*"Interested persons" (as defined in the Investment Company Act of 1940, as
amended (the "1940 Act")) of the Adviser, whose address is 500 Boylston Street,
Boston, Massachusetts 02116.
 
   
Each Trustee and officer holds comparable positions with certain MFS affiliates
or with certain other funds of which MFS or a subsidiary of MFS is the
investment adviser or distributor. Messrs. Shames, Scott, and Cavan, are the
Chairman, a Director and the Secretary, respectively, of MFD, and hold similar
positions with certain other MFS affiliates. Mr. Bailey is a Director of Sun
Life Assurance Company of Canada (U.S.), a subsidiary of Sun Life Assurance
Company of Canada ("Sun Life").
    
 
   
Each Fund pays the compensation of non-interested Trustees and Mr. Bailey (who
currently receive a fee of $2,500 and $250 per year plus $135 and $25 per
meeting and $100 and $20 per committee meeting attended, from the MFS Money
Market Fund and the MFS Government Money Market Fund, respectively, together
with such Trustee's out-of-pocket expenses) and has adopted a retirement plan
for non-interested Trustees and Mr. Bailey. Under this plan, a Trustee will
retire upon reaching age 73 and if the Trustee has completed at least 5 years of
service, he would be entitled to annual payments during his lifetime of up to
50% of such Trustee's average annual compensation (based on the three years
prior to his retirement) depending on his length of service. A Trustee may also
retire prior to age 73 and receive reduced payments if he has completed at least
5 years of service. Under the plan, a Trustee (or his beneficiaries) will also
receive benefits for a period of time in the event the Trustee is disabled or
dies. These benefits will also be based on the Trustee's average annual
compensation and length of service. There is no retirement plan provided by the
Trust for Messrs. Scott and Shames. The Trust will accrue its allocable share of
compensation expenses each year to cover current years service and amortize past
service costs.
    
 
                                        4
<PAGE>   36
 
                              TRUSTEE COMPENSATION
 
                             MFS MONEY MARKET FUND
 
   
<TABLE>
<CAPTION>
                                                                      RETIREMENT BENEFIT                     TOTAL TRUSTEE
                                                       TRUSTEE FEES       ACCRUED AS         ESTIMATED         FEES FROM
                                                           FROM          PART OF FUND      CREDITED YEARS      FUND AND
                       TRUSTEE                           FUND(1)          EXPENSE(1)       OF SERVICE(2)    FUND COMPLEX(3)
                       -------                         ------------   ------------------   --------------   ---------------
<S>                                                    <C>            <C>                  <C>              <C>
Richard B. Bailey....................................     $4,160            $1,017                8            $242,022
Peter G. Harwood.....................................      4,980               796                5             121,105
J. Atwood Ives.......................................      4,230             1,017               17             108,720
Lawrence T. Perera...................................      4,250             1,560               26             127,055
William Poorvu.......................................      4,575             1,580               25             121,105
Charles W. Schmidt...................................      4,170             1,572               20             121,105
Arnold D. Scott......................................          0                 0              N/A                   0
Jeffrey L. Shames....................................          0                 0              N/A                   0
Elaine R. Smith......................................      4,940             1,133               27             132,035
David B. Stone.......................................      4,965             1,650               12             127,055
</TABLE>
    
 
- ---------------
 
   
(1) For fiscal year ended August 31, 1998.
    
 
(2) Based on normal retirement age of 73. See the table below for the estimated
     annual benefits payable upon retirement by the Fund to a Trustee based on
     his or her estimated credited years of service.
 
   
(3) For calendar year 1997. All Trustees receiving compensation served as
     Trustees of 27 funds within the MFS fund complex (having aggregate net
     assets at December 31, 1997, of approximately $29 billion) except Mr.
     Bailey, who served as Trustee of 69 funds within the MFS fund complex
     (having aggregate net assets at December 31, 1997, of approximately $47.8
     billion).
    
 
          ESTIMATED ANNUAL BENEFITS PAYABLE BY FUND UPON RETIREMENT(4)
 
   
<TABLE>
<CAPTION>
                                  YEARS OF SERVICE
    AVERAGE         --------------------------------------------
  TRUSTEE FEES       3          5           7         10 OR MORE
  ------------       -          -           -         ----------
  <S>               <C>       <C>         <C>         <C>
     $3,744         $562      $  936      $1,310        $1,872
      4,091          614       1,023       1,432        $2,045
      4,438          666       1,109       1,553        $2,219
      4,784          718       1,196       1,675        $2,392
      5,131          770       1,283       1,796        $2,566
      5,478          822       1,370       1,917        $2,739
</TABLE>
    
 
- ---------------
 
(4) Other funds in the MFS fund complex provide similar retirement benefits to
     the Trustees.
 
                                        5
<PAGE>   37
 
                              TRUSTEE COMPENSATION
 
                        MFS GOVERNMENT MONEY MARKET FUND
 
   
<TABLE>
<CAPTION>
                                                                      RETIREMENT BENEFIT                     TOTAL TRUSTEE
                                                       TRUSTEE FEES       ACCRUED AS         ESTIMATED         FEES FROM
                                                           FROM          PART OF FUND      CREDITED YEARS      FUND AND
                       TRUSTEE                           FUND(1)          EXPENSE(1)       OF SERVICE(2)    FUND COMPLEX(3)
                       -------                         ------------   ------------------   --------------   ---------------
<S>                                                    <C>            <C>                  <C>              <C>
Richard B. Bailey....................................      $477              $137                  8           $242,022
Peter G. Harwood.....................................       617               111                  5            121,105
J. Atwood Ives.......................................       512               140                 17            108,720
Lawrence T. Perera...................................       487               211                 26            127,055
William Poorvu.......................................       542               219                 25            121,105
Charles W. Schmidt...................................       467               219                 19            121,105
Arnold D. Scott......................................         0                 0                N/A                  0
Jeffrey L. Shames....................................         0                 0                N/A                  0
Elaine R. Smith......................................       622               157                 27            132,035
David B. Stone.......................................       612               209                 11            127,055
</TABLE>
    
 
- ---------------
 
   
(1) For fiscal year ended August 31, 1998.
    
 
(2) Based on normal retirement age of 73. See the table below for the estimated
     annual benefits payable upon retirement by the Fund to a Trustee based on
     his or her estimated credited years of service.
 
   
(3) For calendar year 1997. All Trustees receiving compensation served as
     Trustees of 27 funds within the MFS fund complex (having aggregate net
     assets at December 31, 1997, of approximately $29 billion) except Mr.
     Bailey, who served as Trustee of 69 funds within the MFS fund complex
     (having aggregate net assets at December 31, 1997, of approximately $47.8
     billion.
    
 
          ESTIMATED ANNUAL BENEFITS PAYABLE BY FUND UPON RETIREMENT(4)
 
   
<TABLE>
<CAPTION>
                               YEARS OF SERVICE
    AVERAGE         ---------------------------------------
  TRUSTEE FEES       3        5         7        10 OR MORE
  ------------       -        -         -        ----------
  <S>               <C>      <C>       <C>       <C>
      $420          $63      $105      $147         $210
       473           71       118       166         $237
       526           79       131       184         $263
       579           87       145       203         $289
       631           95       158       221         $316
       684          103       171       239         $342
</TABLE>
    
 
- ---------------
 
(4) Other funds in the MFS fund complex provide similar retirement benefits to
     the Trustees.
 
                                        6
<PAGE>   38
 
   
As of October 30, 1997, all Trustees and officers as a group owned less than 1%
of the shares of the MFS Money Market Fund, and owned 9.6% of the shares of the
MFS Government Money Market Fund (not including 4,056,836 shares representing
approximately 9.5% of the outstanding shares of the MFS Government Money Market
Fund owned of record by certain employee benefit plans of MFS of which Messrs.
Scott and Shames are Trustees).
    
 
   
As of October 30, 1998, Nationwide Life Insurance Company, Dept. 1748, P.O. Box
16786, Columbus, OH 43216-6786, was the record holder of approximately 7.08% of
the outstanding shares of the MFS Money Market Fund, which it held for the
benefit of its policy holders.
    
 
   
As of October 30, 1998, MFS Defined Contribution Plan, c/o Massachusetts
Financial Services Company, 500 Boylston Street, Boston, MA 02116-3740, was the
record owner of approximately 7.94% of the outstanding shares of MFS Government
Money Market Fund.
    
 
The Trust's Declaration of Trust provides that it will indemnify its Trustees
and officers against liabilities and expenses incurred in connection with
litigation in which they may be involved because of their offices with the
Trust, unless, as to liabilities to the Trust or its shareholders, it is finally
adjudicated that they engaged in willful misfeasance, bad faith, gross
negligence or reckless disregard of the duties involved in their offices, or
with respect to any matter, unless it is adjudicated that they did not act in
good faith in the reasonable belief that their actions were in the best interest
of the Trust. In the case of settlement, such indemnification will not be
provided unless it has been determined by a court or other body approving the
settlement or other disposition or by a reasonable determination based upon a
review of readily available facts by vote of a majority of disinterested
Trustees or in a written opinion of independent counsel, that such officers or
Trustees have not engaged in willful misfeasance, bad faith, gross negligence or
reckless disregard of their duties.
 
INVESTMENT ADVISER
 
   
MFS and its predecessor organizations have a history of money management dating
from 1924. MFS is a subsidiary of Sun Life of Canada (U.S.) Financial Services
Holdings, Inc., which in turn is an indirect wholly owned subsidiary of Sun
Life. The Prospectus contains information with respect to the management of the
Adviser and other investment companies for which MFS serves as investment
adviser.
    
 
The Adviser manages each Fund pursuant to an Amended and Restated Investment
Advisory Agreement dated August 1, 1993 (the "Advisory Agreement"). Under the
Advisory Agreement, the Adviser provides each Fund with overall investment
advisory services. Subject to such policies as the Trustees may determine, the
Adviser makes investment decisions for each Fund. For these services and
facilities, the Adviser receives a management fee computed and paid monthly at
the annual rate of 0.5% of the first $300 million of the average aggregate net
assets of the MFS Money Market Fund and the MFS Government Money Market Fund;
0.45% of the next $400 million of such assets; 0.4% of the next $300 million of
such assets; and 0.35% of such assets in excess of $1 billion.
 
   
For the years ended August 31, 1998, 1997 and 1996, MFS received management fees
under the Funds' Advisory Agreement of $3,293,238, $2,793,401 and $2,374,567,
respectively, from the MFS Money Market Fund, and $238,557, $188,007 and
$205,023, respectively, from the MFS Government Money Market Fund. The Trust's
advisory fee is allocated between the MFS Money Market Fund and the MFS
Government Money Market Fund in the ratio each fund's average daily net assets
bears to the aggregate average daily net assets of the Trust.
    
 
   
Each Fund pays all of its expenses (other than those assumed by MFS) including:
Trustees fees discussed above; governmental fees; interest charges; taxes;
membership dues in the Investment Company Institute allocable to the Trust; fees
and expenses of independent auditors, of legal counsel, and of any transfer
agent, registrar or dividend disbursing agent of the Trust; expenses of
repurchasing and redeeming shares; expenses of preparing, printing and mailing
prospectuses, shareholder reports, notices, proxy statements and reports to
governmental officers and commissions; expenses connected with the execution,
recording and settlement of portfolio security transactions; insurance premiums;
fees and expenses of State Street Bank and Trust Company, each Fund's Custodian,
for all services to each Fund, including safekeeping of funds and securities and
maintaining required books and accounts; expenses of calculating the net asset
value of shares of each Fund; expenses of shareholder meetings; and expenses
relating to the issuance, registration and qualification of shares of each Fund.
Such expenses are allocated between the MFS Money Market Fund and the MFS
Government Money Market Fund in a manner believed to be fair and equitable to
each. For a list of the Trust's expenses, including the compensation paid to
Trustees who are not officers of MFS, during the Trust's fiscal year ended
August 31, 1998, see the financial statements included in the Funds' Annual
Report to Shareholders which is incorporated by reference into this SAI.
    
 
   
The Adviser pays the compensation of the Trust's officers and of the Trustees
who are officers of the Adviser. The Adviser also furnishes at its own expense
all necessary administrative services, including office space, equipment,
clerical personnel, investment advisory facilities, and all executive and
supervisory personnel necessary for managing the Trust's investments, effecting
its portfolio transactions.
    
 
   
The Advisory Agreement will remain in effect until August 1, 1999, and will
continue in effect thereafter only if such continuance is specifically approved
at least annually by the Board of Trustees or by vote of a majority of the
Fund's outstanding voting securities and, in either case, by a majority of the
Trustees who are not parties to the Advisory Agreement or interested persons of
any such party. The Advisory Agreement terminates automatically if it is
assigned and may be terminated without penalty by vote of a majority of a Fund's
outstanding voting securities or by either party on not more than 60 days' nor
less than 30 days' written notice. The Advisory Agreement
    
 
                                        7
<PAGE>   39
 
further provides that the Adviser may render services to others and that neither
the Adviser nor its personnel shall be liable for any error of judgment or
mistake of law or for any loss arising out of any investment or for any act or
omission in the execution and management of the Fund, except for willful
misfeasance, bad faith or gross negligence in the performance of its or their
duties or by reason of reckless disregard of its or their obligations and duties
under the Advisory Agreement.
 
ADMINISTRATOR
 
   
MFS provides each Fund with certain financial, legal, compliance, shareholder
communications and other administrative services pursuant to a Master
Administrative Services Agreement dated March 1, 1997, as amended. Under the
Agreement, each Fund pays MFS an administrative fee up to 0.015% per annum of
the Fund's average daily net assets. This fee reimburses MFS for a portion of
the costs it incurs to provide such services. For the period from March 1, 1997
through August 31, 1997 and for fiscal year ended August 31, 1998, MFS received
fees under the Agreement of $45,890 and $98,748 for MFS Money Market Fund and
$2,916, and $6,702 for MFS Government Money Market Fund, respectively.
    
 
DISTRIBUTOR
 
   
MFD, a wholly owned subsidiary of MFS, serves as distributor for the continuous
offering of shares of each Fund pursuant to a Distribution Agreement, dated
January 1, 1995 (the "Distribution Agreement").
    
 
   
The Distribution Agreement will remain in effect until August 1, 1999, and will
continue in effect thereafter only of such continuance is specifically approved
at least annually by the Board of Trustees or by vote of a majority of the
Trust's shares (as defined in "Investment Restrictions") and, in either case, by
a majority of the Trustees who are not parties to the Distribution Agreement or
interested persons of any such party. The Distribution Agreement terminates
automatically if it is assigned and may be terminated without penalty by either
party on not more than 60 days' nor less than 30 days' notice.
    
 
CUSTODIAN
 
State Street Bank and Trust Company (the "Custodian") is the custodian of each
Fund's assets. The Custodian's responsibilities include safekeeping and
controlling the Funds' cash and securities, handling the receipt and delivery of
securities, determining income and collecting interest and dividends on the
Funds' investments, maintaining books of original entry for portfolio and fund
accounting and other required books and accounts, and calculating the daily net
income on shares of the Funds. The Custodian does not determine the investment
policies of the Funds or decide which securities the Funds will buy or sell. The
Funds may, however, invest in securities of the Custodian and may deal with the
Custodian as principal in securities transactions. The Custodian also acts as
the dividend disbursing agent of the Trust.
 
SHAREHOLDER SERVICING AGENT
 
   
MFS Service Center, Inc. (the "Shareholder Servicing Agent" or the "Agent"), a
wholly owned subsidiary of MFS, is the Trust's shareholder servicing agent,
pursuant to a Shareholder Servicing Agreement, effective August 1, 1985, as
amended (the "Agency Agreement") with the Trust. The Agent's responsibilities
under the Agency Agreement include administering and performing transfer
functions and keeping records in connection with the issuance, transfer and
redemption of the shares of the Trust. For these services, the Agent will
receive a fee calculated as a percentage of the average daily net assets of each
Fund at an effective annual rate of 0.1125%. In addition, the Agent will be
reimbursed by the Trust for certain expenses incurred by the Agent on behalf of
the Trust. State Street Bank and Trust Company, the dividend disbursing agent of
the Trust, has contracted with the Shareholder Servicing Agent to administer and
perform certain dividend and distribution disbursing agent functions for the
Trust.
    
 
4. PORTFOLIO TRANSACTIONS AND
   BROKERAGE COMMISSIONS
 
Specific decisions to purchase or sell securities for each Fund are made by the
Funds' portfolio manager who is an employee of the Adviser and who is appointed
and supervised by its senior officers. Changes in the Funds' investments are
reviewed by the Board of Trustees. The Funds' portfolio manager may serve other
clients of the Adviser or any subsidiary of the Adviser in a similar capacity.
 
The primary consideration in placing portfolio security transactions for each
series is "best execution," i.e., execution at the most favorable prices and in
the most effective manner possible. The Adviser at all times attempts to achieve
"best execution," and it has complete freedom as to the markets in and the
broker-dealers through which it seeks this result. It is expected that most
transactions will be with the issuer or with major dealers acting for their own
account and not as brokers. Subject to the requirement of seeking "best
execution," securities may be bought from or sold to broker-dealers who have
furnished research and investment services to the Adviser. Such research and
investment services are those which brokerage houses customarily provide to
institutional investors and include statistical and economic data and research
reports on particular companies and industries. In placing orders with such
broker-dealers the Adviser will, where possible, take into account the
comparative usefulness of such research and investment services. Such research
and investment services are useful to the Adviser even though their dollar value
may be indeterminable and their receipt or availability generally does not
reduce the Adviser's normal research activities or expenses. From time to time,
the Adviser may also direct certain portfolio transactions to broker-dealer
firms which, in turn, have agreed to pay a portion of the Funds' operating
expenses (e.g., fees charged by the Custodian of the Funds' assets).
 
Consistent with the foregoing primary consideration, the Conduct Rules of the
National Association of Securities Dealers,
 
                                        8
<PAGE>   40
 
Inc., and such other policies as the Trustees may determine, the Adviser may
consider sales of shares of the Trust and of other investment company clients of
MFS as a factor in the selection of broker-dealers to execute the Trust's
portfolio transactions.
 
   
For each Fund's fiscal years ended August 31, 1998, 1997 and 1996, neither Fund
paid brokerage commissions.
    
 
   
During the period ended August 31, 1998, the MFS Money Market Fund acquired
securities issued by Merrill Lynch & Co., J.P. Morgan & Co., Nationsbank & Co.,
Goldman Sachs & Co., and Associates Corp. of N. America, regular broker-dealers
of the Fund, which securities had a value of $19,955,358, $19,204,389,
$25,729,987, $19,974,945 and $50,000,000, respectively, as of August 31, 1998.
    
 
   
During the period ended August 31, 1998, the MFS Government Money Market Fund
acquired securities issued by Goldman Sachs & Co., a regular broker-dealer of
the Fund, which had a value of $3,740,000 as of August 31, 1998.
    
 
In certain instances there may be securities which are suitable for one or both
of the Trust's portfolios as well as for that of one or more of the other
clients of the Adviser or any subsidiary of the Adviser. Investment decisions
for each Fund and for such other clients are made with a view to achieving their
respective investment objectives. It may develop that a particular security is
bought or sold for only one client even though it might be held by, or bought or
sold for, other clients. Likewise, a particular security may be bought for one
or more clients when one or more other clients are selling that same security.
Some simultaneous transactions are inevitable when several clients receive
investment advice from the same investment adviser, particularly when the same
security is suitable for the investment objectives of more than one client. When
two or more clients are simultaneously engaged in the purchase or sale of the
same security, the securities are allocated among clients in a manner believed
by the Adviser to be equitable to each. It is recognized that in some cases this
system could have a detrimental effect on the price or volume of the security as
far as either Fund is concerned. In other cases, however, the Trust believes
that the ability of each Fund to participate in volume transactions will produce
better executions for that Fund.
 
5. SHAREHOLDER SERVICES
 
INVESTMENT AND WITHDRAWAL PROGRAMS: Each Fund makes available the following
programs designed to enable shareholders to add to their investment or withdraw
from it with a minimum of paper work. The programs involve no extra charge to
shareholders other than a sales charge in the case of certain share purchases
and may be changed or discontinued at any time by a shareholder or the Fund.
 
SUBSEQUENT INVESTMENT BY TELEPHONE: Each shareholder may purchase additional
shares of any MFS Fund by telephoning the Shareholder Servicing Agent toll-free
at (800) 225-2606. The minimum purchase amount is $50 and the maximum purchase
amount is $100,000. Shareholders wishing to avail themselves of this telephone
purchase privilege must so elect on their Account Application and designate
thereon a bank and account number from which purchases will be made. If a
telephone purchase request is received by the Shareholder Servicing Agent on any
business day prior to the close of regular trading on the Exchange (generally,
4:00 p.m., Eastern time), the purchase will occur at the closing net asset value
of the shares purchased on that day. The Shareholder Servicing Agent may be
liable for any losses resulting from unauthorized telephone transactions if it
does not follow reasonable procedures designed to verify the identity of the
caller. The Shareholder Servicing Agent will request personal or other
information from the caller, and will normally also record calls. Shareholders
should verify the accuracy of confirmation statements immediately after their
receipt.
 
DISTRIBUTION INVESTMENT PROGRAM: Distributions of dividends made by either Fund
may be automatically invested in shares of one of the other funds in the MFS
Family of Funds (the "MFS Funds"), if shares of the fund are available for sale.
Such investments will be subject to initial investment minimums, as well as
additional purchase minimums. Distributions invested in one of the other MFS
Funds will be invested at net asset value (exclusive of any sales charge).
Distributions will be invested at the close of business on the payable date for
the distribution. A shareholder considering the Distribution Investment Program
should obtain and read the prospectus of the other fund and consider the
differences in objectives and policies before making any investment.
 
SYSTEMATIC WITHDRAWAL PLAN: A shareholder may direct the Shareholder Servicing
Agent to send him (or anyone he designates) regular monthly, quarterly or
semi-annual payments based upon the value of his account. Each payment under a
Systematic Withdrawal Plan ("SWP") must be at least $100, except in certain
limited circumstances. Such payments are drawn from the proceeds of the
redemption of shares held in the shareholder's account. To the extent that
redemptions for such periodic withdrawals exceed dividend income reinvested in
the account, such redemptions will reduce and may eventually exhaust the number
of shares in the shareholder's account. To initiate this service, a shareholder
must own 5,000 or more shares of the Fund. The shareholder may deposit into the
account additional shares of the Fund, change the payee or change the dollar
amount of each payment. The Fund may terminate any SWP for an account if the
number of shares in the account falls below 5,000 as a result of share
redemptions (other than as a result of a SWP) or an exchange of shares of the
Fund for shares of another MFS Fund. Any such plan may be terminated at any time
by either the shareholder or the Fund.
 
AUTOMATIC EXCHANGE PLAN: Shareholders having account balances of at least $5,000
in any MFS Fund may exchange their shares for the same class of shares of other
MFS Funds under the Automatic Exchange Plan. The Automatic Exchange Plan
provides for automatic monthly or quarterly exchanges of funds from the
shareholder's Fund account for investment in the same class of shares of other
MFS Funds selected by the shareholder. Under the Automatic Exchange Plan,
exchanges of at least $50 each may be made to up to six different funds
effective on the
 
                                        9
<PAGE>   41
 
seventh day of each month or of every third month, depending on whether monthly
or quarterly exchanges are elected by the shareholder. If the seventh day of the
month is not a business day, the transaction will be processed on the next
business day. Generally, the initial exchange will occur after receipt and
processing by the Shareholder Servicing Agent of an application in good order.
Exchanges will continue to be made from a shareholder's account in the Fund as
long as the balance of the account is sufficient to complete the exchanges.
Additional payments made to a shareholder's account will extend the period that
exchanges will continue to be made under the Automatic Exchange Plan. However,
if additional payments are added to an account subject to the Automatic Exchange
Plan shortly before an exchange is scheduled, such funds may not be available
for exchanges until the following month; therefore, care should be used to avoid
inadvertently terminating the Automatic Exchange Plan through exhaustion of the
account balance.
 
No transaction fee for exchanges will be charged in connection with the
Automatic Exchange Plan. However, exchanges of shares of the Funds will be
subject to any applicable sales charge. Changes in amounts to be exchanged to
each fund, the funds to which exchanges are to be made, and the timing of
exchanges (monthly or quarterly), or the termination of a shareholder's
participation in the Automatic Exchange Plan, will be made after instructions in
writing or by telephone (an "Exchange Change Request") are received by the
Shareholder Servicing Agent in proper form (i.e., if in writing -- signed by the
record owner(s) exactly as shares are registered; if by telephone -- proper
account identification is given by the dealer or shareholder of record). Each
Exchange Change Request (other than termination of participation in the program)
must involve at least $50. Generally, if an Exchange Change Request is received
by telephone or in writing before the close of business on the last business day
of a month, the Exchange Change Request will be effective for the following
month's exchange.
 
A shareholder's right to make additional investments in any of the MFS Funds, to
make exchanges of shares from one MFS Fund to another and to withdraw from an
MFS Fund, as well as a shareholder's other rights and privileges are not
affected by a shareholder's participation in the Automatic Exchange Plan.
 
The Automatic Exchange Plan is part of the Exchange Privilege. For additional
information regarding the Automatic Exchange Plan, see "Exchange Privilege"
below.
 
INVEST BY MAIL OR WIRE: Additional investments of $50 or more may be made at any
time either by mailing a check payable to the Fund directly to the Shareholder
Servicing Agent or by wire, as described in the Funds' Prospectus under the
caption "Information Concerning Shares of the Funds -- Opening an Account: By
Wire." The shareholder's account number must be included with each investment.
 
REINSTATEMENT PRIVILEGE: Shareholders of the Funds who have redeemed their
shares (other than shares acquired through direct purchase or reinvested
dividends) and shareholders of the other MFS Funds who have redeemed their
shares have a one-time right to reinvest the redemption proceeds in shares of
any of the MFS Funds (if shares of the fund are available for sale) at net asset
value (without a sales charge) and, if applicable, with credit for any CDSC
paid. In the case of proceeds reinvested in the money market funds, the
shareholder has the right to exchange such shares for shares of another MFS Fund
at net asset value pursuant to the exchange privilege described below. Such a
reinvestment must be made within 90 days of the redemption and is limited to the
amount of the redemption proceeds. If the shares credited for any CDSC paid are
then redeemed within 12 months of the initial purchase, such CDSC will be
imposed upon redemption. Although redemptions and repurchases of shares are
taxable events, a reinvestment within such 90-day period in the same fund may be
considered a "wash sale" and may result in the inability to recognize currently
all or a portion of any loss realized on the original redemption for federal
income tax purposes. Please see your tax advisor for further information.
 
EXCHANGE PRIVILEGE:  Shares of either Fund which are acquired through direct
purchase for which payment has been received by the Fund (i.e., an established
account) may be exchanged at net asset value for shares of the other Fund.
However, shares of either Fund may be redeemed and shares of any of the other
MFS Funds acquired at net asset value plus their normal sales charge. Shares of
either Fund acquired by an exchange from any of the other MFS Funds or by
automatic reinvestment of Fund dividends paid after June 1, 1992, may be
exchanged for shares of any of such other MFS Funds (if available for sale).
 
Exchanges will be made only after instructions in writing or by telephone (an
"Exchange Request") are received for an established account by the Shareholder
Servicing Agent in proper form (i.e., if in writing -- signed by the record
owner(s) exactly as the shares are registered; if by telephone -- proper account
identification is given by the dealer or shareholder of record), and each
exchange must involve shares having an aggregate value of at least $1,000 ($50
in the case of retirement plan participants whose sponsoring organizations
subscribe to the MFS FUNDamental 401(k) Plan or another similar 401(k)
recordkeeping system made available by the Shareholder Servicing Agent) or all
the shares in the account. If the Exchange Request is received by the
Shareholder Servicing Agent in writing or by telephone on any business day prior
to the close of regular trading on the Exchange, the exchange will usually occur
that day if all the requirements set forth above have been complied with at that
time. No more than five exchanges may be made in any one Exchange Request by
telephone. The exchange privilege (or any aspect of it) may be changed or
discontinued and is subject to certain limitations, including certain
restrictions on purchases by market timer accounts (see "Purchases" in the
Prospectus). Required forms are available from the Shareholder Servicing Agent
or investment dealers.
 
Additional information with respect to any of the MFS Funds, including a copy of
its current prospectus, may be obtained from investment dealers or the
Shareholder Servicing Agent. A shareholder should obtain and read the prospectus
of the other MFS
                                       10
<PAGE>   42
 
Fund and consider the differences in objectives and policies before making any
exchange. Unitholders of the MFS Fixed Fund (a bank collective investment fund)
have the right to exchange their units (except units acquired through direct
purchases) for shares of either Fund, subject to the conditions, if any, imposed
upon such unitholders by the MFS Fixed Fund.
 
Any state income tax advantage for investment in shares of each portfolio of MFS
Municipal Series Trust and may only benefit residents of such states. Investors
should consult with their own tax advisers to be sure this is an appropriate
investment, based on their residency and each state's income tax laws.
 
   
TAX-DEFERRED RETIREMENT PLANS -- Shares of either Fund may be purchased by all
types of tax-deferred retirement plans. MFD makes available, through investment
dealers, plans and/or custody agreements, the following:
    
 
   
  Traditional Individual Retirement Accounts (IRAs) (for individuals who desire
  to make limited contributions to a tax-deferred retirement program and, if
  eligible, to receive a federal income tax deduction for amounts contributed);
    
 
   
  Roth Individual Retirement Accounts (Roth IRAs) (for individuals who desire to
  make limited contributions to a tax-favored retirement program);
    
 
  Simplified Employee Pension (SEP-IRA) Plans;
 
  403(b) Plans (deferred compensation arrangements for employees of public
  school systems and certain non-profit organizations); and
 
  Certain other qualified pension and profit-sharing plans.
 
The plan documents provided by MFD designate The First National Bank of Boston
as trustee or custodian (unless another trustee or custodian is designated by
the individual or group establishing the plan) and contain specific information
about the plans. Each plan provides that dividends and distributions will be
reinvested automatically. For further details with respect to any plan,
including fees charged by The First National Bank of Boston or MFD, tax
consequences and redemption information, see the specific documents for that
plan. Plan documents other than those provided by MFD may be used to establish
any of the plans described above. Third party administrative services, available
for some corporate plans, may limit or delay the processing of transactions.
 
Investors should consult with their tax advisers before establishing any of the
tax-deferred retirement plans described above.
 
6. TAX STATUS
 
   
Each Fund has elected to be treated and intends to qualify year as a "regulated
investment company" under Subchapter M of the Internal Revenue Code of 1986, as
amended, (the "Code") by meeting all applicable requirements of Subchapter M,
including requirements as to the nature of each Fund's gross income, the amount
of each Fund's distributions, and the composition of each Fund's portfolio
assets. Because each Fund intends to distribute all of its net investment income
and net realized capital gains to shareholders in accordance with the timing
requirements imposed by the Code, it is not expected that either Fund will be
required to pay any federal income or excise taxes, although the MFS Money
Market Fund's foreign source income may be subject to foreign withholding taxes.
If a Fund should fail to qualify as a "regulated investment company" in any
year, that Fund would incur a regular corporate federal income tax upon its
taxable income and its distributions would generally be taxable as ordinary
dividend income to its shareholders.
    
 
   
Shareholders of each Fund will normally have to pay federal income taxes, and
any state or local income taxes, on the dividends they receive from that Fund.
Dividends from ordinary income are taxable to shareholders as ordinary income
for federal income tax purposes, whether the distributions are paid in cash or
reinvested in additional shares. Because the Funds expect to earn primarily
interest income, it is expected that no Fund dividends will qualify for the
dividends received deduction for corporations. Any Fund dividend that is
declared in October, November or December of any calendar year, that is payable
to shareholders of record in such a month, and that is paid the following
January will be treated as if received by the shareholders on December 31 of the
year in which the dividend is declared. Each Fund will notify shareholders
regarding the federal tax status of its distributions after the end of each
calendar year.
    
 
Each Fund's current dividend and accounting policies will affect the amount,
timing and character of distributions to shareholders.
 
Special tax considerations apply with respect to foreign investments of the MFS
Money Market Fund. Foreign exchange gains and losses realized by that Fund will
generally be treated as ordinary income and losses. Investment income received
by the MFS Money Market Fund from foreign securities may be subject to foreign
income taxes withheld at the source; the Fund does not expect to be able to pass
through to shareholders foreign tax credits with respect to such foreign taxes.
The United States has entered into tax treaties with many foreign countries that
may entitle the MFS Money Market Fund to a reduced rate of tax or an exemption
from tax on such income; the Fund intends to qualify for treaty reduced rates
where available. It is not possible, however, to determine the Fund's effective
rate of foreign tax in advance since the amounts of the Fund's assets to be
invested within various countries are not known.
 
Dividends and certain other payments to persons who are not citizens or
residents of the United States or U.S. entities ("Non-U.S. Persons") are
generally subject to U.S. tax withholding at the rate of 30%. The Funds intend
to withhold U.S. federal income tax payments at the rate of 30% (or any lower
rate permitted under an applicable treaty) on taxable dividends and other
payments to Non-U.S. Persons that are subject to such withholding. Any amounts
overwithheld may be recovered by such persons by filing a claim for refund with
the U.S. Internal Revenue Service within the time period appropriate to such
claims. Distributions received from a Fund by Non-U.S. Persons also may be
subject to tax under the laws of their own
 
                                       11
<PAGE>   43
 
jurisdictions. Each Fund is also required in certain circumstances to apply
backup withholding at the rate of 31% on taxable dividends paid to any
shareholder (including a Non-U.S. Person) who does not furnish to the Fund
certain information and certifications or who is otherwise subject to backup
withholding. Backup withholding will not, however, be applied to payments that
have been subject to 30% withholding.
 
As long as a Fund qualifies as a regulated investment company under the Code, it
will not be required to pay Massachusetts income or excise taxes.
 
   
Distributions of each Fund that are derived from interest on obligations of the
U.S. Government and certain of its agencies and instrumentalities (but generally
not from capital gains realized upon the disposition of such obligations) may be
exempt from state and local taxes. Each Fund intends to advise shareholders of
the extent, if any, to which its distributions consist of such interest.
Residents of certain states may be subject to an intangibles tax or a personal
property tax on all or a portion of the value of their shares. Shareholders are
urged to consult their tax advisers regarding the possible exclusion of such
portion of their dividends for state and local income tax purposes as well as
regarding the tax consequences of an investment in the Fund.
    
 
7. DESCRIPTION OF SHARES, VOTING RIGHTS AND LIABILITIES
 
The Trust presently has four series of shares and has reserved the right to
create additional series of shares. The Trustees have authorized the issuance of
one class of shares for each of the Funds, Class A and Class B shares of a third
series, and Class A, Class B, Class C and Class I shares of a fourth series of
the Trust. Each share of a series represents an equal proportionate interest in
that series with each other share of that series. The shares of each series
participate equally in the earnings, dividends and assets of the particular
portfolio. Shares have no pre-emptive or conversion rights. Shares when issued
are fully paid and non-assessable. Shareholders are entitled to one vote for
each share held. Shares of each series vote separately to approve investment
advisory agreements or changes in investment objective or restrictions, but
shares of all series vote together in the election of Trustees and the selection
of accountants. Although Trustees are not elected annually by the shareholders,
shareholders have under certain circumstances the right to remove one or more
Trustees. Shareholders of each series would be entitled to share pro rata in the
net assets of their respective portfolio available for distribution to
shareholders upon liquidation of the Trust or that series.
 
The Trust may merge or consolidate with another organization or sell all or
substantially all its assets, if approved by the vote of the holders of
two-thirds of the outstanding shares of the Trust, except that if the Trustees
recommend such merger, consolidation or sale, the approval by vote of the
holders of a majority of the Trust's outstanding shares will be sufficient. The
Trust may be terminated upon liquidation and distribution of the assets of the
Trust, if approved by the vote of the holders of two-thirds of the outstanding
shares of the Trust. If not so terminated, the Trust will continue indefinitely.
 
The Trust is an entity of the type commonly known as a "Massachusetts business
trust." Under Massachusetts law, shareholders of such a trust may, under certain
circumstances, be held personally liable as partners for its obligations.
However, the Declaration of Trust contains an express disclaimer of shareholder
liability for acts or obligations of the Trust and provides for indemnification
and reimbursement of expenses out of the Trust property for any shareholder held
personally liable for the obligations of the Trust. The Declaration of Trust
also provides that the Trust shall maintain appropriate insurance (for example,
fidelity bonding and errors and omissions insurance) for the protection of the
Trust, its shareholders, Trustees, officers, employees and agents covering
possible tort and other liabilities. Thus, the risk of a shareholder incurring
financial loss on account of shareholder liability is limited to circumstances
in which both inadequate insurance existed and the Trust itself was unable to
meet its obligations.
 
The Declaration of Trust further provides that obligations of the Trust are not
binding upon the Trustees individually but only upon the property of the Trust
and that the Trustees will not be liable for any action or failure to act, but
nothing in the Declaration of Trust protects a Trustee against any liability to
which he would otherwise be subject by reason of willful misfeasance, bad faith,
gross negligence, or reckless disregard of the duties involved in the conduct of
his office.
 
8. NET INCOME AND DISTRIBUTIONS
 
The Net Income of each Fund is determined each day during which the Exchange is
open for trading. (As of the date of this SAI, the Exchange is open for trading
every weekday except for the following holidays or the days on which they are
observed: New Year's Day, Martin Luther King, Jr., Day, Presidents' Day, Good
Friday, Memorial Day, Independence Day, Labor Day, Thanksgiving Day and
Christmas Day.) This determination is made once during each such day as of the
close of regular trading on the Exchange. All the Net Income, as defined below,
of each Fund so determined is declared in shares of the respective Fund as a
dividend to shareholders of record of that Fund at the time of such
determination. Shares purchased become entitled to dividends declared as of the
first day following the date of investment. Dividends are generally distributed
on the last business day of each month in the form of additional shares of the
respective Fund at the rate of one share (and fraction thereof) for each one
dollar (and fraction thereof) of dividend income attributable to that Fund, or,
at the election of the shareholder, in cash; except that if a shareholder
redeems the entire amount in his account with that Fund at any time during the
month, all dividends declared on that Fund during the month through the date of
redemption will be paid to him at the same time as the proceeds from the
redemption of his shares.
 
For this purpose the Net Income of either Fund (from the time of the immediately
preceding determination thereof) shall con-
 
                                       12
<PAGE>   44
 
sist of (i) all interest income accrued on the portfolio assets of that Fund,
(ii) less all actual and accrued expenses of that Fund determined in accordance
with generally accepted accounting principles, and (iii) plus or minus net
realized gains and losses and net unrealized appreciation or depreciation on the
assets of that Fund. Interest income shall include discount earned (including
both original issue and market discount) on discount paper accrued ratably to
the date of maturity. Securities are valued at amortized cost, which the
Trustees have determined in good faith constitutes fair value for the purposes
of complying with the 1940 Act. This valuation method will continue to be used
until such time as the Trustees determine that it does not constitute fair value
for such purposes. The Trust will limit the portfolio investments of each Fund
to those U.S. dollar-denominated instruments which the Board of Trustees or its
delegate determines present minimal credit risks, and which are of high quality
as determined by the 1940 Act and the rules thereunder. The Trust has also
agreed to maintain a dollar weighted average maturity for each series of 90 days
or less and to invest only in securities maturing in 13 months or less. The
Board of Trustees has also established procedures designed to stabilize the net
asset value per share of each series, as computed for the purposes of sales and
redemptions, at $1.00 per share. If the Trustees determine that a deviation from
the $1.00 per share price may exist which may result in a material dilution or
other unfair result to investors or existing shareholders, they will take such
corrective action as they regard as necessary and appropriate, which action
could include the sale of instruments prior to maturity (to realize capital
gains or losses); shortening average portfolio maturity; withholding dividends;
or using market quotations for valuation purposes.
 
Since the Net Income of each Fund is declared as a dividend each time the Net
Income of that Fund is determined, the net asset value per share of that Fund
(i.e., the value of the net assets of that Fund divided by the number of shares
of that Fund outstanding) remains at $1.00 per share immediately after each such
determination and dividend declaration. Any increase in the value of a
shareholder's investment in either Fund, representing the reinvestment of
dividend income, is reflected by an increase in the number of shares of that
Fund in his account.
 
It is expected that each Fund will have a positive Net Income at the time of
each determination thereof. If for any reason the Net Income of either Fund
determined at any time is a negative amount, which could occur, for instance,
upon default by an issuer of a portfolio security, that Fund would first offset
the negative amount with respect to each shareholder account in that Fund from
the dividends declared during the month with respect to each such account. If
and to the extent that such negative amount exceeds such declared dividends at
the end of the month (or during the month in the case of an account liquidated
in its entirety), that Fund could reduce the number of its outstanding shares by
treating each shareholder of that Fund as having contributed to its capital that
number of full and fractional shares of that Fund in the account of such
shareholder which represents his proportion of such excess. Each shareholder of
that Fund will be deemed to have agreed to such contribution in these
circumstances by his investment in that Fund. This procedure would permit the
net asset value per share of each Fund to be maintained at a constant $1.00 per
share.
 
9. PERFORMANCE INFORMATION
 
YIELD INFORMATION. Each Fund will provide current annualized and effective
annualized yield quotations based on the daily dividends of the particular Fund.
These quotations may from time to time be used in advertisements, shareholder
reports or other communications to shareholders. However, these yield quotations
should not be considered as representative of the yield of either Fund in the
future since the yield of each Fund will vary based on the type, quality and
maturities of the securities held in the portfolio of the particular Fund,
fluctuations in short-term interest rates and changes in the Fund's expenses.
 
   
The current annualized yield of the MFS Money Market Fund for the seven-day
period ended August 31, 1998 (the end of the Trust's fiscal year) was 4.92% and
the effective annualized yield of the MFS Money Market Fund for such period was
5.04%. The current annualized yield of the MFS Government Money Market Fund for
that seven-day period was 4.77% and the effective annualized yield of the MFS
Government Money Market Fund for that period was 4.88%. Current yield and
account balance information may be obtained by calling 1-800-MFS-TALK
(637-8255).
    
 
Any current yield quotation of either Fund which is used in such a manner as to
be subject to the provisions of Rule 482(d), under the Securities Act of 1933,
as amended, shall consist of an annualized historical yield, carried at least to
the nearest hundredth of one percent, based on a specific seven calendar day
period and shall be calculated by dividing the net change in the value of an
account having a balance of one share at the beginning of the period by the
value of the account at the beginning of the period and multiplying the quotient
by 365/7. For this purpose the net change in account value would reflect the
value of additional shares purchased with dividends declared on the original
share and dividends declared on both the original share and any such additional
shares, but would not reflect any realized gains or losses from the sale of
securities or any unrealized appreciation or depreciation on portfolio
securities. In addition, any effective yield quotation of either Fund so used
shall be calculated by compounding the current yield quotation for such period
by multiplying such quotation by 7/365, adding 1 to the product, raising the sum
to a power equal to 365/7, and subtracting 1 from the result.
 
GENERAL: From time to time each Fund may, as appropriate, quote Fund rankings or
reprint all or a portion of evaluations of fund performance and operations
appearing in various independent publications, including but not limited to the
following: Money, Fortune, U.S. News and World Report, Kiplinger's Personal
Finance, The Wall Street Journal, Barron's Investors Business Daily, Newsweek,
Financial World, Financial Planning, Investment Advisor, USA Today, Pensions and
Investments, SmartMoney, Forbes, Global Finance, Registered Representative,
Institutional Investor, the Investment Company Institute,
                                       13
<PAGE>   45
 
Johnson's Charts, Morningstar, Lipper Analytical Services, Inc., CDA
Wiesenberger, Shearson Lehman and Salomon Bros. Indices, Ibbotson, Business
Week, Lowry Associates, Media General, Investment Company Data, The New York
Times, Your Money, Strangers Investment Advisor, Financial Planning on Wall
Street, Standard and Poor's, Individual Investor, The 100 Best Mutual Funds You
Can Buy by Gordon K. Williamson, Consumer Price Index, and Sanford C. Bernstein
& Co. Fund performance may also be compared to the performance of other mutual
funds tracked by financial or business publications or periodicals.
 
From time to time, each Fund may discuss or quote its current portfolio manager
as well as other investment personnel, including such persons' views on: the
economy; securities markets; portfolio securities and their issuers; investment
philosophies, strategies, techniques and criteria used in the selection of
securities to be purchased or sold for the Fund; the Fund's portfolio holdings;
the investment research and analysis process; the formulation and evaluation of
investment recommendations; and the assessment and evaluation of credit,
interest rate, market and economic risks, and similar or related matters.
 
Each Fund may also quote evaluations mentioned in independent radio or
television broadcasts.
 
From time to time each Fund may use charts and graphs to illustrate the past
performance of various indices such as those mentioned above and illustrations
using hypothetical rates of return to illustrate the effects of compounding and
tax-deferral.
 
From time to time the Fund may also discuss or quote the views of its
distributor, its investment adviser and other financial planning, legal, tax,
accounting, insurance, estate planning and other professionals, or from surveys,
regarding individual and family financial planning. Such views may include
information regarding: retirement planning; tax management strategies; estate
planning; general investment techniques (e.g., asset allocation and disciplined
saving and investing); business succession; ideas and information provided
through the MFS Heritage Panning(SM) program, an intergenerational financial
planning assistance program; issues with respect to insurance (e.g., disability
and life insurance and Medicare supplemental insurance); issues regarding
financial and health care management for elderly family members; and other
similar or related matters.
 
MFS FIRSTS: MFS has a long history of innovations.
 
  --  1924 -- Massachusetts Investors Trust is established as the first open-end
      mutual fund in America.
 
  --  1924 -- Massachusetts Investors Trust is the first mutual fund to make
      full public disclosure of its operations in shareholder reports.
 
  --  1932 -- One of the first internal research departments is established to
      provide in-house analytical capability for an investment management firm.
 
  --  1933 -- Massachusetts Investors Trust is the first mutual fund to register
      under the Securities Act of 1933 ("Truth in Securities Act" or "Fund
      Disclosure Act").
 
  --  1936 -- Massachusetts Investors Trust is the first mutual fund to allow
      shareholders to take capital gain distributions either in additional
      shares or in cash.
 
  --  1976 -- MFS(R) Municipal Bond Fund is among the first municipal bond funds
      established.
 
  --  1979 -- Spectrum becomes the first combination fixed/variable annuity with
      no initial sales charge.
 
   
  --  1981 -- MFS(R) Global Governments Fund is established as America's first
      globally diversified fixed-income mutual fund.
    
 
  --  1984 -- MFS(R) Municipal High Income Fund is the first open-end mutual
      fund to seek high tax-free income from lower-rated municipal securities.
 
  --  1986 -- MFS(R) Managed Sectors Fund becomes the first mutual fund to
      target and shift investments among industry sectors for shareholders.
 
  --  1986 -- MFS(R) Municipal Income Trust is the first closed-end, high-yield
      municipal bond fund traded on the New York Stock Exchange.
 
  --  1987 -- MFS(R) Multimarket Income Trust is the first closed-end,
      multimarket high income fund listed on the New York Stock Exchange.
 
  --  1989 -- MFS(R) Regatta becomes America's first non-qualified
      market-value-adjusted fixed/variable annuity.
 
   
  --  1990 -- MFS(R) Global Total Return Fund is the first global balanced fund.
    
 
   
  --  1993 -- MFS(R) Global Growth Fund is the first global emerging markets
      fund to offer the expertise of two sub-advisers.
    
 
   
  --  1993 -- MFS(R) becomes money manager of MFS(R) Union Standard(R) Equity
      Fund, the first Fund to invest solely in companies deemed to be
      union-friendly by an advisory board of senior labor officials, senior
      managers of companies with significant labor contracts, academics and
      other national labor leaders or experts.
    
 
10. INDEPENDENT AUDITORS AND
     FINANCIAL STATEMENTS
 
Deloitte & Touche LLP are the Funds' independent auditors, providing audit
services, tax return preparation, and assistance and consultation with respect
to the preparation of filings with the SEC.
 
   
The Portfolios of Investments at August 31, 1998, the Statements of Assets and
Liabilities at August 31, 1998, the Statements of Operations for the year ended
August 31, 1998, the Statements of Changes in Net Assets for the years ended
August 31, 1998 and 1997, the Notes to Financial Statements and the Independent
Auditors' Report, each of which is included in the Annual Report to shareholders
of the Funds, are incorporated by reference into this SAI and have been so
incorporated in reliance upon the report of Deloitte & Touche LLP, independent
auditors, as experts in accounting and auditing. A copy of the Annual Report
accompanies this SAI.
    
 
                                       14
<PAGE>   46
 
                                                                      APPENDIX A
 
   
DESCRIPTION OF STANDARD & POOR'S RATINGS SERVICES ("S&P"), FITCH IBCA ("FITCH")
AND MOODY'S INVESTORS SERVICE, INC. ("MOODY'S") HIGHEST COMMERCIAL PAPER AND
BOND RATINGS:
    
 
A-1 AND P-1 COMMERCIAL PAPER RATINGS
 
   
The ratings "A-1" and "F1" are the highest commercial paper ratings assigned by
S&P and Fitch, respectively, and issues so rated are regarded as having the
greatest capacity for timely payment. Issues in these "A" and "F" categories are
delineated with the numbers 1, 2 and 3 to indicate the relative degree of
safety. For example, the A-1 designation indicates that the degree of safety
regarding timely payment is strong. Those A-1 issues determined to possess
extremely strong safety characteristics will be denoted with a plus (+) sign
designation.
    
 
The rating P-1 is the highest commercial paper rating assigned by Moody's.
Issuers rated P-1 (or supporting institutions) have a superior ability for
repayment of senior short-term debt obligations. P-1 repayment ability will
often be evidenced by many of the following characteristics: (1) leading market
positions in well-established industries; (2) high rates of return on funds
employed; (3) conservative capitalization structure with moderate reliance on
debt and ample asset protection; (4) broad margins in earnings coverage of fixed
financial charges and high internal cash generation; (5) well-established access
to a range of financial markets and assured sources of alternate liquidity.
 
AAA, AA AND Aaa, Aa BONDS RATINGS
 
Debt rated AA by S&P and Fitch are judged by S&P to be high-quality obligations,
and differ only in small degree from issues rated AAA. AAA is S&P and Fitch's
highest rating and indicates an extremely strong capacity to pay interest and
repay principal. Bonds rated Aa by Moody's are judged by Moody's to be of high
quality by all standards. Together with the Aaa group they comprise what are
generally known as high-grade bonds. They are rated lower than Aaa securities
because margins of protection may not be as large as in Aaa securities or
fluctuation of protective elements may be of greater amplitude or there may be
other elements present which make the long-term risks appear somewhat larger
than in Aaa securities.
 
                                       A-1
<PAGE>   47
 
INVESTMENT ADVISER
Massachusetts Financial Services Company
500 Boylston Street, Boston, MA 02116
(617) 954-5000
 
DISTRIBUTOR
MFS Fund Distributors, Inc.
500 Boylston Street, Boston, MA 02116
(617) 954-5000
 
CUSTODIAN AND DIVIDEND DISBURSING AGENT
State Street Bank and Trust Company
225 Franklin Street, Boston, MA 02110
 
SHAREHOLDER SERVICING AGENT
MFS Service Center, Inc.
500 Boylston Street, Boston, MA 02116
Toll free: (800) 225-2606
 
Mailing Address:
P.O. Box 2281, Boston, MA 02107
 
INDEPENDENT AUDITORS
Deloitte & Touche LLP
125 Summer Street, Boston, MA 02110
 
MFS(R) MONEY
MARKET FUND
 
MFS(R) GOVERNMENT
MONEY MARKET FUND
 
500 BOYLSTON STREET
BOSTON, MA 02116
 
[MFS LOGO]
<PAGE>   48
 
   
<TABLE>
<S>                                   <C>
    
   
MFS(R) MUNICIPAL                                                   PROSPECTUS
BOND FUND                                                     JANUARY 1, 1999
(A member of the MFS Family of          CLASS A SHARES OF BENEFICIAL INTEREST
Funds(R))                               CLASS B SHARES OF BENEFICIAL INTEREST
</TABLE>
    
 
- --------------------------------------------------------------------------------
500 Boylston Street, Boston, Massachusetts 02116      (617) 954-5000
 
This Prospectus pertains to the MFS Municipal Bond Fund (the "Fund"), a
diversified series of MFS Series Trust IV (the "Trust"), an open-end investment
company presently consisting of four series. The investment objective of the
Fund is to provide as high a level of current income exempt from federal income
taxes as is considered consistent with prudent investing while seeking
protection of shareholders' capital (see "Investment Objective and Policies").
The minimum initial investment generally is $1,000 per account (see "Information
Concerning Shares of the Fund -- Purchases").
 
The Fund's investment adviser and distributor are Massachusetts Financial
Services Company ("MFS" or the "Adviser") and MFS Fund Distributors, Inc.
("MFD"), respectively, both of which are located at 500 Boylston Street, Boston,
Massachusetts 02116.
 
                                                        (continued on next page)
 
INVESTMENT PRODUCTS ARE NOT INSURED BY THE FDIC OR ANY OTHER GOVERNMENT AGENCY,
AND ARE NOT DEPOSITS OR OTHER OBLIGATIONS OF, OR GUARANTEED BY, ANY FINANCIAL
INSTITUTION. SHARES OF MUTUAL FUNDS ARE SUBJECT TO INVESTMENT RISK, INCLUDING
POSSIBLE LOSS OF THE PRINCIPAL AMOUNT INVESTED, AND WILL FLUCTUATE IN VALUE. YOU
MAY RECEIVE MORE OR LESS THAN YOU PAID WHEN YOU REDEEM YOUR SHARES.
 
  THESE SECURITIES HAVE NOT BEEN APPROVED OR DISAPPROVED BY THE SECURITIES AND
 EXCHANGE COMMISSION OR ANY STATE SECURITIES COMMISSION NOR HAS THE SECURITIES
   AND EXCHANGE COMMISSION OR ANY STATE SECURITIES COMMISSION PASSED UPON THE
          ACCURACY OR ADEQUACY OF THIS PROSPECTUS. ANY REPRESENTATION
                     TO THE CONTRARY IS A CRIMINAL OFFENSE.
 
   INVESTORS SHOULD READ THIS PROSPECTUS AND RETAIN IT FOR FUTURE REFERENCE.
<PAGE>   49
 
(continued from previous page)
 
   
This Prospectus sets forth concisely the information concerning the Fund that a
prospective investor ought to know before investing. The Fund has filed with the
Securities and Exchange Commission (the "SEC") a Statement of Additional
Information, dated January 1, 1999, as amended or supplemented from time to time
(the "SAI"), which contains more detailed information about the Fund. The SAI is
incorporated into this Prospectus by reference. See page 33 for a further
description of the information set forth in the SAI. A copy of the SAI may be
obtained without charge by contacting the Shareholder Servicing Agent (see back
cover for address and phone number). The SEC maintains an Internet World Wide
Web site (http://www.sec.gov) that contains the SAI, materials that are
incorporated by reference into this Prospectus and the SAI, and other
information regarding the Fund. This Prospectus is available on the Adviser's
Internet World Wide Web site at http://www.mfs.com.
    
 
TABLE OF CONTENTS
 
   
<TABLE>
<CAPTION>
                                                                  PAGE
                                                                  ----
<S>  <C>                                                          <C>
1.   Expense Summary............................................     3
2.   Condensed Financial Information............................     5
3.   The Fund...................................................     7
4.   Investment Objective and Policies..........................     8
5.   Management of the Fund.....................................    13
6.   Year 2000 Issues...........................................    15
7.   Information Concerning Shares of the Fund..................    15
          Purchases.............................................    15
          Exchanges.............................................    22
          Redemptions and Repurchases...........................    23
          Distribution Plan.....................................    27
          Distributions.........................................    28
          Tax Status............................................    28
          Net Asset Value.......................................    29
          Description of Shares, Voting Rights and
               Liabilities......................................    30
          Performance Information...............................    30
          Provision of Annual and Semiannual Reports............    31
8.   Shareholder Services.......................................    31
     Appendix A.................................................   A-1
     Appendix B.................................................   B-1
     Appendix C.................................................   C-1
</TABLE>
    
 
                                        2
<PAGE>   50
 
1.  EXPENSE SUMMARY
 
<TABLE>
<CAPTION>
                                                      CLASS A         CLASS B
SHAREHOLDER TRANSACTION EXPENSES:                     -------         -------
<S>                                                <C>                <C>
    Maximum Initial Sales Charge Imposed on
      Purchases of Fund Shares (as a
      percentage of offering price)..........              4.75%      0.00%
    Maximum Contingent Deferred Sales Charge
      (as a percentage of original purchase
      price or redemption proceeds, as
      applicable)............................       See Below(1)      4.00%
</TABLE>
 
   
ANNUAL OPERATING EXPENSES OF THE FUND (AS A PERCENTAGE OF AVERAGE NET ASSETS):
 
<TABLE>
<S>                                                <C>                <C>
    Management Fees..........................              0.40%      0.40%
    Rule 12b-1 Fees..........................              0.00%      0.80%(2)
    Other Expenses(3)........................              0.20%      0.20%
                                                           -----      -----
    Total Operating Expenses.................              0.60%      1.40%
</TABLE>
    
 
- ---------------
(1) Purchases of $1 million or more are not subject to an initial sales charge;
    however, a contingent deferred sales charge (a "CDSC") of 1% will be imposed
    on such purchases in the event of certain redemption transactions within 12
    months following such purchases (see "Information Concerning Shares of the
    Fund -- Purchases" below).
(2) The Fund has adopted a distribution plan for its Class B shares in
    accordance with Rule 12b-1 under the Investment Company act of 1940, as
    amended (the "1940 Act") (the "Distribution Plan"), which provides that it
    will pay distribution/service fees aggregating up to (but not necessarily
    all of) 1.00% per annum of the average daily net assets attributable to the
    Class B shares (see "Information Concerning Shares of the
    Fund -- Distribution Plan" below). Except in the case of the 0.25% per annum
    Class B service fee paid by the Fund in connection with the sale of Class B
    shares, payment of the Class B service fee will be suspended until such date
    as the Trustees of the Trust may determine. Distribution expenses paid under
    this Plan, together with any CDSC payable upon redemption of Class B shares,
    may cause long-term shareholders to pay more than the maximum sales charge
    that would have been permissible if imposed entirely as an initial sales
    charge.
(3) The Fund has an expense offset arrangement which reduces the Fund's
    custodian fee based upon the amount of cash maintained by the Fund with its
    custodian and dividend disbursing agent, and may enter into other such
    arrangements and directed brokerage arrangements (which would also have the
    effect of reducing the Fund's expenses). Any such fee reductions are not
    reflected under "Other Expenses."
 
                                        3
<PAGE>   51
 
                              EXAMPLE OF EXPENSES
 
An investor would pay the following dollar amounts of expenses on a $1,000
investment in the Fund, assuming (a) a 5% annual return and (b) redemption at
the end of each of the time periods indicated (unless otherwise noted):
 
   
<TABLE>
<CAPTION>
             PERIOD                CLASS A         CLASS B
             ------                -------      --------------
<S>                                <C>          <C>       <C>
                                                           (1)
 1 year..........................   $ 53        $ 54      $ 14
 3 years.........................     66          74        44
 5 years.........................     80          97        77
10 years.........................    120         146(2)    146(2)
</TABLE>
    
 
- ---------------
(1) Assumes no redemption.
 
(2) Class B shares convert to Class A shares approximately eight years after
    purchase; therefore, years nine and ten reflect Class A expenses.
 
   
    The purpose of the expense table above is to assist investors in
understanding the various costs and expenses that a shareholder of the Fund will
bear directly or indirectly. More complete descriptions of the following Fund
expenses are set forth in the following sections: (i) varying sales charges on
share purchases -- "Purchases"; (ii) varying CDSCs -- "Purchases"; (iii)
management fees -- "Management of the Fund" and (iv) Rule 12b-1 (i.e.,
distribution plan) fees -- "Distribution Plan."
    
 
THE "EXAMPLE" SET FORTH ABOVE SHOULD NOT BE CONSIDERED A REPRESENTATION OF PAST
OR FUTURE EXPENSES OF THE FUND; ACTUAL EXPENSES MAY BE GREATER OR LESS THAN
THOSE SHOWN.
 
                                        4
<PAGE>   52
 
2.  CONDENSED FINANCIAL INFORMATION
 
The following information has been audited for at least the latest five fiscal
years of the Fund and should be read in conjunction with the financial
statements included in the Fund's Annual Report to shareholders which are
incorporated by reference into the SAI in reliance upon the report of the Fund's
independent auditors, given upon their authority as experts in accounting and
auditing. The Fund's current independent auditors are Deloitte & Touche LLP.
 
   
                              FINANCIAL HIGHLIGHTS
    
 
   
<TABLE>
<CAPTION>
                                                                                  TEN
                                                                                 MONTHS
                                                YEAR ENDED AUGUST 31,            ENDED      YEAR ENDED
                                          ----------------------------------   AUGUST 31,   OCTOBER 31,
                                           1998      1997     1996     1995       1994         1993
                                           ----      ----     ----     ----    ----------   -----------
                                          CLASS A
                                          -------
<S>                                       <C>       <C>      <C>      <C>      <C>          <C>
Per share data (for a share outstanding
 throughout each period):
Net asset value -- beginning of
 period.................................  $10.99    $10.75   $10.83   $10.68    $ 11.64       $10.73
                                          ------    ------   ------   ------    -------       ------
Income from investment operations# --
   Net investment income................  $ 0.54    $ 0.57   $ 0.59   $ 0.60    $  0.51       $ 0.61
   Net realized and unrealized gain
     (loss) on investments..............    0.28      0.24    (0.09)    0.15      (0.77)        1.14
                                          ------    ------   ------   ------    -------       ------
Total from investment operations........  $ 0.82    $ 0.81   $ 0.50   $ 0.75    $ (0.26)      $ 1.75
                                          ------    ------   ------   ------    -------       ------
Less distributions declared to
 shareholders --
   From net investment income...........  $(0.54)   $(0.57)  $(0.58)  $(0.60)   $ (0.47)      $(0.66)
   From net realized gain on
     investments........................   (0.18)       --       --       --      (0.16)       (0.15)
   In excess of net investment income...      --        --       --       --      (0.04)       (0.03)
   In excess of net realized gain on
     investments........................      --        --       --       --      (0.03)          --
                                          ------    ------   ------   ------    -------       ------
Total distributions declared to
 shareholders...........................  $(0.72)   $(0.57)  $(0.58)  $(0.60)   $ (0.70)      $(0.84)
                                          ------    ------   ------   ------    -------       ------
Net asset value -- end of period........  $11.09    $10.99   $10.75   $10.83    $ 10.68       $11.64
                                          ======    ======   ======   ======    =======       ======
Total return+++.........................   7.78%     7.75%    4.67%    7.31%     (2.33)%++       16.97%
Ratios (to average net assets)/
 Supplemental data:
   Expenses##...........................   0.60%     0.60%    0.60%    0.61%      0.59%+       0.59%
   Net investment income................   4.90%     5.29%    5.37%    5.70%      5.49%+       5.63%
Portfolio turnover......................     79%       91%      84%      90%        74%          56%
Net assets at end of period (000,000
 omitted)...............................  $1,639    $1,660   $1,798   $1,949    $ 2,031       $2,195
</TABLE>
    
 
- ---------------
 
   
<TABLE>
<C>  <S>
  +  Annualized.
 ++  Not annualized.
  #  Per share data for the periods subsequent to October 31,
     1993 are based on average shares outstanding.
 ##  For fiscal years ending after September 1, 1995, the Fund's
     expenses are calculated without reduction for fees paid
     indirectly.
+++  Total returns for Class A shares do not include the
     applicable sales charge. If the charge had been included,
     the results would have been lower.
</TABLE>
    
 
                                        5
<PAGE>   53
 
                              FINANCIAL HIGHLIGHTS
 
   
<TABLE>
<CAPTION>
                                                       YEAR ENDED OCTOBER 31,
                                             -------------------------------------------
                                              1992      1991     1990     1989     1988
                                              ----      ----     ----     ----     ----
                                             CLASS A
                                             ------
<S>                                          <C>       <C>      <C>      <C>      <C>
Per share data (for a share outstanding
  throughout each period):
Net asset value -- beginning of period.....  $10.80    $10.11   $10.53   $10.57   $ 9.71
                                             ------    ------   ------   ------   ------
Income from investment operations --
    Net investment income..................  $ 0.66    $ 0.68   $ 0.68   $ 0.72   $ 0.73
    Net realized and unrealized gain (loss)
      on investments.......................    0.09      0.69    (0.13)    0.04     0.86
                                             ------    ------   ------   ------   ------
Total from investment operations...........  $ 0.75    $ 1.37   $ 0.55   $ 0.76   $ 1.59
                                             ------    ------   ------   ------   ------
Less distributions declared to
  shareholders --
    From net investment income.............  $(0.66)   $(0.68)  $(0.69)  $(0.72)  $(0.73)
    From net realized gain on
      investments..........................   (0.16)       --    (0.27)      --       --
    In excess of net investment income.....      --        --       --    (0.08)      --
    From paid-in capital...................      --        --    (0.01)      --       --
                                             ------    ------   ------   ------   ------
Total distributions declared to
  shareholders.............................  $(0.82)   $(0.68)  $(0.97)  $(0.80)  $(0.73)
                                             ------    ------   ------   ------   ------
Net asset value -- end of period...........  $10.73    $10.80   $10.11   $10.53   $10.57
                                             ======    ======   ======   ======   ======
Total return++.............................   7.35%    13.85%    5.42%    7.54%   16.95%
Ratios (to average net assets)/
  Supplemental data:
    Expenses...............................   0.57%     0.59%    0.60%    0.64%    0.65%
    Net investment income..................   6.12%     6.47%    6.69%    6.87%    7.16%
Portfolio turnover.........................     87%       98%     160%     199%     190%
Net assets at end of period (000,000
  omitted).................................  $1,878    $1,715   $1,409   $1,259   $1,003
</TABLE>
    
 
- ---------------
 
   
<TABLE>
<S>  <C>
++   Total returns for Class A shares do not include the
     applicable sales charge. If the charge had been included,
     the results would have been lower.
</TABLE>
    
 
                                        6
<PAGE>   54
 
                              FINANCIAL HIGHLIGHTS
 
   
<TABLE>
<CAPTION>
                                                                           TEN
                                                                          MONTHS        PERIOD
                                         YEAR ENDED AUGUST 31,            ENDED         ENDED
                                   ----------------------------------   AUGUST 31,   OCTOBER 31,
                                    1998      1997     1996     1995       1994         1993*
                                    ----      ----     ----     ----    ----------   -----------
                                   CLASS B
                                   -------
<S>                                <C>       <C>      <C>      <C>      <C>          <C>
Per share data (for a share
  outstanding throughout each
  period):
Net asset value -- beginning of
  period.........................  $10.99    $10.74   $11.10   $10.67    $  11.63       $11.68
                                   ------    ------   ------   ------    --------       ------
Income from investment
  operations# --
    Net investment income........  $ 0.45    $ 0.48   $ 0.49   $ 0.49    $   0.40       $ 0.07
    Net realized and unrealized
      gain (loss) on
      investments................    0.28      0.25    (0.37)    0.16       (0.77)       (0.05)
                                   ------    ------   ------   ------    --------       ------
Total from investment
  operations.....................  $ 0.73    $ 0.73   $ 0.12   $ 0.65    $  (0.37)      $ 0.02
                                   ------    ------   ------   ------    --------       ------
Less distributions declared to
  shareholders --
    From net investment income...  $(0.46)   $(0.48)  $(0.48)  $(0.49)   $  (0.40)      $(0.07)++++
    From net realized gain on
      investments................   (0.18)       --       --       --       (0.16)          --
    In excess of net realized
      gain on investments........      --        --       --       --       (0.03)          --
                                   ------    ------   ------   ------    --------       ------
Total distributions declared to
  shareholders...................  $(0.64)   $(0.48)  $(0.48)  $(0.49)   $  (0.59)      $(0.07)
                                   ------    ------   ------   ------    --------       ------
Net asset value -- end of
  period.........................  $11.08    $10.99   $10.74   $10.83    $  10.67       $11.63
                                   ======    ======   ======   ======    ========       ======
Total return.....................   6.85%     6.84%    3.69%    6.35%     (3.25)%++      1.49%+
Ratios (to average net assets)/
  Supplemental data:
    Expenses##...................   1.40%     1.46%    1.55%    1.60%       1.72%+       1.70%+
    Net investment income........   4.10%     4.42%    4.42%    4.68%       4.41%+       3.85%+
Portfolio turnover...............     79%       91%      84%      90%         74%          56%
Net assets at end of period
  (000,000 omitted)..............  $   81    $   76   $   71   $   56    $     45       $   10
</TABLE>
    
 
- ---------------
 
   
   * For the period from the inception of Class B, September 7, 1993, through
     October 31, 1993.
    
   
   + Annualized.
    
   
  ++ Not annualized.
    
   
  # Per share data for the periods subsequent to October 31, 1993, are based on
    average shares outstanding.
    
   
 ## For fiscal years ending September 1, 1995, the Fund's expenses are
    calculated without reduction for fees paid indirectly.
    
   
  ++++ Amount includes a per share distribution in excess of net investment
       income of $0.002.
    
 
3.  THE FUND
 
The Fund is a diversified series of the Trust, an open-end management investment
company which was organized as a business trust under the laws of The
Commonwealth of Massachusetts in 1975. The Trust presently consists of four
series, each of which represents a portfolio with separate investment objectives
and policies. Shares of the Fund are continuously sold to the public and the
Fund uses the proceeds to buy securities (primarily municipal bonds and other
 
                                        7
<PAGE>   55
 
instruments the interest on which is exempt from federal income tax) for its
portfolio. Two classes of shares of the Fund currently are offered to the
general public. Class A shares are offered at net asset value plus an initial
sales charge up to a maximum of 4.75% of the offering price (or a CDSC of 1.00%
upon redemption during the first year in the case of purchases of $1 million or
more and certain purchases by retirement plans). Class B shares are offered at
net asset value without an initial sales charge but subject to a CDSC upon
redemption (declining from 4.00% during the first year to 0% after six years)
and an annual distribution fee and a service fee up to a maximum of 1.00% per
annum; Class B shares will convert to Class A shares approximately eight years
after purchase.
 
The Trust's Board of Trustees provides broad supervision over the affairs of the
Fund. The Adviser is responsible for the management of the Fund's assets and the
officers of the Trust are responsible for the Fund's operations. The Adviser
manages the portfolio from day to day in accordance with the Fund's investment
objective and policies. The selection of investments and the way they are
managed depend on the conditions and trends in the economy and the financial
marketplaces. The Fund also offers to buy back (redeem) its shares from its
shareholders at any time at net asset value, less any applicable CDSC.
 
4.  INVESTMENT OBJECTIVE AND POLICIES
 
INVESTMENT OBJECTIVE -- The Fund's investment objective is to provide as high a
level of current income exempt from federal income taxes as is considered
consistent with prudent investing and protection of shareholders' capital. Any
investment involves risk and there can be no assurance that the Fund will
achieve its investment objective. The investment objective and policies may,
unless otherwise specifically stated, be changed without shareholder approval.
 
INVESTMENT POLICIES -- The Fund's policy under normal conditions is to invest
substantially all (i.e., at least 80%) of the Fund's assets in debt securities
issued by or on behalf of states, territories and possessions of the United
States and the District of Columbia and their political subdivisions, agencies
or instrumentalities, the interest on which is exempt from federal income tax
("Municipal Bonds" or "tax-exempt securities"). The interest income on certain
of these obligations may be subject to an alternative minimum tax, which is
considered to be tax-exempt for purposes of the 80% test described above. As a
temporary defensive measure during times of adverse market conditions, up to 50%
of the Fund's assets may be invested in short-term investments described in
paragraphs 3 and 4 below.
 
    The Fund's total assets will be invested in:
 
   
        (1) Tax-exempt securities which are rated AAA, AA or A by Standard &
    Poor's Ratings Services ("S&P"), Duff & Phelps Credit Rating Co. ("Duff &
    Phelps") or by Fitch IBCA ("Fitch"), or are rated Aaa, Aa or A by Moody's
    Investors Service, Inc. ("Moody's");
    
 
   
        (2) Notes of issuers having an issue of outstanding Municipal Bonds
    rated AAA, AA or A by S&P, Duff & Phelps or by Fitch or Aaa, Aa or A by
    Moody's or which are guaranteed by the U.S. Government;
    
 
        (3) Obligations issued or guaranteed by the U.S. Government or its
    agencies or instrumentalities;
 
                                        8
<PAGE>   56
 
        (4) Commercial paper, obligations of banks (including certificates of
    deposit, bankers' acceptances and repurchase agreements) with $1 billion of
    assets, and cash;
 
        (5) Tax-exempt securities which are not rated but which, in the opinion
    of the Adviser, are of at least comparable quality to the three highest
    grades of S&P, Fitch or Moody's; however, not more than 10% of the Fund's
    total assets will be invested in such securities;
 
   
        (6) Tax-exempt securities which are rated BBB by S&P, Fitch or Duff &
    Phelps or are rated Baa by Moody's (and comparable unrated securities);
    however, not more than 40% of the Fund's total assets will be invested in
    such securities.
    
 
   
Interest income from the short-term investments described in paragraphs 3 and 4
above will be taxable to shareholders as ordinary income. For a comparison of
yields on Municipal Bonds and taxable securities, see the Taxable Equivalent
Yield Table in Appendix B to this Prospectus. For a general discussion of
Municipal Bonds and descriptions of short-term investments permitted as
investments and the ratings of S&P, Fitch, Moody's and Duff & Phelps for
Municipal Bonds, see Appendix C to this Prospectus and Appendix A to the
Statement of Additional Information, respectively. Although higher quality
tax-exempt securities may produce lower yields, they are generally more
marketable.
    
 
   
As noted above, the Fund may invest in tax-exempt securities rated Baa by
Moody's or BBB by S&P, Fitch or Duff & Phelps (and comparable unrated
securities). These securities, while normally exhibiting adequate protection
parameters, have speculative characteristics and changes in economic conditions
or other circumstances are more likely to lead to a weakened capacity to make
principal and interest payments than in the case of higher grade tax-exempt
securities. If a security purchased by the Fund is subsequently downgraded to
below BBB by S&P, Fitch or Duff & Phelps or Baa by Moody's or comparable
standards for unrated securities, the security will be sold only if the Adviser
believes it is advantageous to do so.
    
 
The net asset value of the shares of an open-end investment company such as the
Fund, which invests primarily in fixed income tax-exempt securities, changes as
the general levels of interest rates fluctuate. When interest rates decline, the
value of the Fund shares can be expected to rise. Conversely, when interest
rates rise, the value of the Fund shares can be expected to decline.
 
From time to time, proposals have been introduced before Congress for the
purpose of restricting or eliminating the federal income tax exemption for
interest on Municipal Bonds. For the effect of current federal tax law on this
exemption, see the "Tax Status" section of this Prospectus.
 
ZERO COUPON BONDS:  Municipal Bonds in which the Fund may invest also include
zero coupon bonds. Zero coupon bonds are debt obligations which are issued at a
significant discount from face value and do not require the periodic payment of
interest. The discount approximates the total amount of interest the bonds will
accrue and compound over the period until maturity at a rate of interest
reflecting the market rate of the security at the time of issuance. Zero coupon
bonds benefit the issuer by mitigating its need for cash to meet debt service,
but also require a higher rate of return to attract investors who are willing to
defer receipt of such cash. Such investments may experience greater volatility
in market value due to changes in interest rates than debt obligations which
make regular payments of interest. The Fund will accrue income on such
investments for tax and accounting purposes, as required, which is distributable
to
 
                                        9
<PAGE>   57
 
shareholders and which, because no cash is received at the time of accrual, may
require the liquidation of other portfolio securities to satisfy the Fund's
distribution obligations.
 
REPURCHASE AGREEMENTS:  The Fund may enter into repurchase agreements in order
to earn income on available cash or as a temporary defensive measure. Under a
repurchase agreement, the Fund acquires securities subject to the seller's
agreement to repurchase at a specified time and price. If the seller becomes
subject to a proceeding under the bankruptcy laws or its assets are otherwise
subject to a stay order, the Fund's right to liquidate the securities may be
restricted (during which time the value of the securities could decline). As
discussed in the SAI, the Fund has adopted certain procedures intended to
minimize risk.
 
   
RESTRICTED SECURITIES:  The Fund may also purchase securities that are not
registered under the Securities Act of 1933, as amended (the "1933 Act"),
("restricted securities") but can be offered and sold to "qualified
institutional buyers" under Rule 144A under the 1933 Act ("Rule 144A
Securities"). A determination is made based upon a continuing review of the
trading markets for the specific Rule 144A Security, whether such a security is
liquid and thus not subject to the Fund's limitation on investing not more than
15% of its net assets in illiquid investments. The Board of Trustees has adopted
guidelines and delegated to the Adviser the daily function of determining and
monitoring liquidity of Rule 144A Securities. The Board, however, retains
oversight of the liquidity determinations, focusing on factors such as
valuation, liquidity and availability of information. Investing in Rule 144A
Securities could have the effect of decreasing the level of liquidity in the
Fund to the extent that qualified institutional buyers become for a time
uninterested in purchasing Rule 144A Securities held in the Fund's portfolio.
Subject to the Fund's 15% limitation on investments in illiquid investments, the
Fund may also invest in restricted securities that may not be sold under Rule
144A, which presents certain risks. As a result, the Fund might not be able to
sell these securities when the Adviser wishes to do so, or might have to sell
them at less than fair value. In addition, market quotations are less readily
available. Therefore, the judgment of the Adviser may at times play a greater
role in valuing these securities than in the case of unrestricted securities.
    
 
"WHEN-ISSUED" SECURITIES:  Some tax-exempt securities may be purchased on a
"when-issued" or on a "forward delivery" basis, which means that the securities
will be delivered to the Fund at a future date, usually beyond customary
settlement time. The commitment to purchase a security for which payment will be
made on a future date may be deemed a separate security. The Fund does not pay
for the securities until received and does not start earning interest on them
until the contractual settlement date. While awaiting delivery of securities
purchased on such bases, the Fund will segregate liquid assets sufficient to
cover its commitments. For additional information concerning the use, risks and
costs of "when-issued" and "forward delivery" securities, see the Fund's
Statement of Additional Information.
 
INVERSE FLOATING RATE OBLIGATIONS:  The Fund may invest in so-called "inverse
floating rate obligations" or "residual interest" bonds, or other obligations or
certificates structured to have similar features. Such obligations generally
have floating or variable interest rates that move in the opposite direction of
short-term interest rates and generally increase or decrease in value in
response to changes in short-term interest rates at a rate which is a multiple
(typically two) of the rate at which fixed-rate long-term tax-exempt securities
increase or decrease in response to
 
                                       10
<PAGE>   58
 
such changes. As a result, such obligations have the effect of providing
investment leverage and may be more volatile than fixed-rate long-term
tax-exempt obligations.
 
OPTIONS:  The Fund may write (sell) "covered" put and call options on fixed
income securities. Call options written by the Fund give the holder the right to
buy the underlying securities from the Fund at a fixed exercise price up to a
stated expiration date or, in the case of certain options, on such date. Put
options written by the Fund give the holder the right to sell the underlying
securities to the Fund during the term of the option at a fixed exercise price
up to a stated expiration date or, in the case of certain options, on such date.
Call options are "covered" by the Fund, for example, when it owns the underlying
securities, and put options are "covered" by the Fund, for example, when it has
established a segregated account of liquid assets which can be liquidated
promptly to satisfy any obligation of the Fund to purchase the underlying
securities. The Fund may also write straddles (combinations of puts and calls on
the same underlying security). The writing of straddles generates additional
premium income but may present greater risk.
 
The Fund will receive a premium from writing a put or call option, which
increases the Fund's gross income in the event the option expires unexercised or
is closed out at a profit. The amount of the premium will reflect, among other
things, the relationship of the exercise price to the market price and
volatility of the underlying security, the remaining term of the option, supply
and demand and interest rates. By writing a call option, the Fund limits its
opportunity to profit from any increase in the market value of the underlying
security above the exercise price of the option. By writing a put option, the
Fund assumes the risk that it may be required to purchase the underlying
security for an exercise price higher than its then-current market value,
resulting in a potential capital loss unless the security subsequently
appreciates in value.
 
The Fund may terminate an option that it has written prior to its expiration by
entering into a closing purchase transaction in which it purchases an option
having the same terms as the option written. It is possible, however, that
illiquidity in the options markets may make it difficult from time to time for
the Fund to close out its written option positions.
 
The Fund may also purchase put or call options in anticipation of changes in
interest rates which may adversely affect the value of its portfolio or the
prices of securities that the Fund wants to purchase at a later date. The
premium paid for a put or call option plus any transaction costs will reduce the
benefit, if any, realized by the Fund upon exercise of the option, and, unless
the price of the underlying security changes sufficiently, the option may expire
without value to the Fund.
 
In addition, the Fund may purchase warrants on fixed income securities. A
warrant on a fixed income security is a long-dated call option conveying to the
holder of the warrant the right, but not the obligation, to purchase a fixed
income security of a specific description from the issuer on a certain date or
dates (the exercise date) at a fixed exercise price.
 
The Fund intends to write and purchase options on securities primarily for
hedging purposes and also in an effort to increase current income. Options on
securities, including warrants, that are written or purchased by the Fund will
be traded on U.S. securities exchanges and over-the-counter.
 
FUTURES CONTRACTS AND OPTIONS ON FUTURES CONTRACTS:  The Fund may purchase and
sell futures contracts on fixed income securities or indices of such securities,
including Municipal Bond
 
                                       11
<PAGE>   59
 
indices and any other indices of fixed income securities which may become
available for trading ("Futures Contracts"). The Fund may also purchase and
write options on such Futures Contracts ("Options on Futures Contracts"). These
instruments will be used to hedge against anticipated future changes in interest
rates which otherwise might either adversely affect the value of the Fund's
portfolio securities or adversely affect the price of securities which the Fund
intends to purchase at a later date. These instruments may also be used for
non-hedging, subject to applicable law. For example, the Fund may sell Futures
Contracts on an index of securities in order to profit from any anticipated
decline in the value of the securities comprising the underlying index. Should
interest rates move in an unexpected manner, however, the Fund may not achieve
the anticipated benefits of the hedging transactions and may realize a loss.
 
   
In order to assure that the Fund will not be deemed to be a "commodity pool" for
purposes of the Commodity Exchange Act, regulations of the Commodity Futures
Trading Commission (the "CFTC") require that the Fund enter into transactions in
Futures Contracts, Options on Futures Contracts and Options on Foreign
Currencies traded on a CFTC-regulated exchange only (i) for bona fide hedging
purposes (as defined in CFTC regulations), or (ii) for non-bona fide hedging
purposes, provided that the aggregate initial margin and premiums required to
establish such non-bona fide hedging positions does not exceed 5% of the
liquidation value of the Fund's assets, after taking into account unrealized
profits and unrealized losses on any such contracts the Fund has entered into,
and excluding, in computing such 5%, the in-the-money amount with respect to an
option that is in-the-money at the time of purchase.
    
 
Futures Contracts and Options on Futures Contracts that are entered into by the
Fund will be traded on U.S. commodities exchanges.
 
RISK FACTORS:  Although the Fund will enter into transactions in Futures
Contracts and Options on Futures Contracts for hedging purposes, and will enter
into certain option transactions for hedging purposes, such transactions
nevertheless involve risks. For example, a lack of correlation between the
instrument underlying an option or Futures Contract and the assets being hedged,
or unexpected adverse price movements, could render the Fund's hedging strategy
unsuccessful and could result in losses. The Fund also may enter into
transactions in options for non-hedging purposes, which involves greater risk.
In particular, such transactions may result in losses for the Fund which are not
offset by gains on other portfolio positions, thereby reducing gross income.
Also, there can be no assurance that a liquid secondary market will exist for
any contract purchased or sold, and the Fund may be required to maintain a
position until exercise or expiration, which could result in a loss. The markets
for such instruments may be extremely volatile from time to time, as discussed
in the SAI, which could increase the risks incurred by the Fund in making such
transactions. The SAI contains a further description of options, Futures
Contracts and Options on Futures Contracts, and a discussion of the risks
related to transactions therein.
 
Transactions in options may be entered into on U.S. exchanges regulated by the
SEC and in the over-the-counter market, while Futures Contracts and Options on
Futures Contracts may be entered into on U.S. commodities exchanges regulated by
the CFTC. Over-the-counter transactions involve certain risks which may not be
present in exchange-traded transactions.
 
Gains recognized from options and futures transactions engaged in by the Fund
are taxable income to shareholders upon distribution.
 
                                       12
<PAGE>   60
 
PORTFOLIO TRADING:  The Fund intends to engage in buying and selling securities,
as well as holding securities to maturity. In buying and selling portfolio
securities, the Fund seeks to take advantage of market developments, yield
disparities and variations in the creditworthiness of issuers. For a description
of the strategies which may be used by the Fund in buying and selling portfolio
securities, see the SAI.
 
The primary consideration in placing portfolio security transactions is
execution at the most favorable price. Consistent with the foregoing primary
consideration, the Conduct Rules of the National Association of Securities
Dealers, Inc. (the "NASD") and such other policies as the Trustees may
determine, the Adviser may consider sales of shares of the Fund and of the other
investment company clients of MFD, the Fund's distributor, as a factor in the
selection of broker-dealers to execute the portfolio transactions of the Fund.
From time to time, the Adviser may direct certain portfolio transactions to
broker dealer firms which, in turn, have agreed to pay a portion of the Fund's
operating expenses (e.g., fees charged by the custodian of the Fund's assets).
For a further discussion of portfolio transactions and brokerage commissions,
see the SAI.
                            ------------------------
 
The SAI includes a discussion of other investment policies and a listing of
specific investment restrictions which govern the Fund's investment policies.
The specific investment restrictions listed in the SAI may be changed without
shareholder approval unless indicated otherwise (see "Investment Restrictions"
in the SAI). Except with respect to the Fund's policies on borrowing and
investing in illiquid securities, the Fund's investment limitations, policies
and rating standards are adhered to at the time of purchase or utilization of
assets; a subsequent change in circumstances will not be considered to result in
a violation of policy.
 
5.  MANAGEMENT OF THE FUND
 
   
INVESTMENT ADVISER -- The Adviser manages the Fund pursuant to an Investment
Advisory Agreement dated September 1, 1993 (the "Advisory Agreement"). Under the
Advisory Agreement, the Adviser provides the Fund with overall investment
advisory services. Geoffrey L. Schecter, a Vice President of the Adviser, has
been the Fund's portfolio manager since March of 1998 and has been employed as a
portfolio manager by the Adviser since 1993. Prior to 1993, Mr. Schecter was a
Senior Investment Analyst at Liberty Mutual Insurance Company. Subject to such
policies as the Trustees may determine, the Adviser makes investment decisions
for the Fund. For these services and facilities, the Adviser receives a
management fee computed and paid monthly on the basis of a formula based upon a
percentage of the Fund's average daily net assets plus a percentage of its gross
income (i.e., income other than gains from the sale of securities) in each case
on an annualized basis for the Fund's then-current fiscal year. The applicable
percentages are reduced as assets and income reach the following levels:
    
 
<TABLE>
<CAPTION>
   ANNUAL RATE OF MANAGEMENT FEE             ANNUAL RATE OF MANAGEMENT FEE
 BASED ON AVERAGE DAILY NET ASSETS               BASED ON GROSS INCOME
- -----------------------------------       -----------------------------------
<S>                                       <C>
 .220% of the first $200 million           4.12% of the first $16 million
 .187% of average daily net assets         3.51% of gross income in excess of
  in excess of $200 million                 $16 million
 .168% of average daily net assets         3.16% of gross income in excess of
  in excess of $2 billion                   $160 million
</TABLE>
 
                                       13
<PAGE>   61
 
   
For the Fund's fiscal year ended August 31, 1998, MFS received management fees
under the Fund's investment advisory agreement of $6,706,665 equivalent on an
annualized basis to 0.40% of the Fund's average daily net assets.
    
 
   
MFS also serves as investment adviser to each of the other funds in the MFS
Family of Funds (the "MFS Funds"), to MFS Municipal Income Trust, MFS Government
Markets Income Trust, MFS Multimarket Income Trust, MFS Intermediate Income
Trust, MFS Charter Income Trust, MFS Special Value Trust, MFS Institutional
Trust, MFS Variable Insurance Trust, MFS/Sun Life Series Trust and seven
variable accounts, each of which is a registered investment company established
by Sun Life Assurance Company of Canada (U.S.), a subsidiary of Sun Life
Assurance Company of Canada ("Sun Life") in connection with the sale of various
fixed/variable annuity contracts. MFS and its wholly owned subsidiary, MFS
Institutional Advisors, Inc., provide investment advice to substantial private
clients.
    
 
   
MFS is America's oldest mutual fund organization. MFS and its predecessor
organizations have a history of money management dating from 1924 and the
founding of the first mutual fund in the United States, Massachusetts Investors
Trust. Net assets under the management of the MFS organization were
approximately $83.1 billion on behalf of approximately 3.5 million accounts as
of September 30, 1998. As of such date, the MFS organization managed
approximately $6.7 billion of assets in municipal obligations and approximately
$20.6 billion of assets in fixed income funds and fixed income portfolios. MFS
is a subsidiary of Sun Life Assurance Company of Canada (U.S.) Financial
Services Holdings, Inc. ("Sun Life of Canada (U.S.)") which in turn is an
indirect wholly owned subsidiary of Sun Life Assurance Company of Canada ("Sun
Life"). The Directors of MFS are John W. Ballen, Thomas J. Cashman, Joseph W.
Dello Russo, John D. McNeil, Kevin H. Parke, Arnold D. Scott, William W. Scott,
Jr., Jeffrey L. Shames and Donald A. Stewart. Mr. Shames is the Chairman and
Chief Executive Officer of MFS, Mr. Ballen is the President and the Chief
Investment Officer of MFS, Mr. Cashman is an Executive Vice President of MFS,
Mr. Dello Russo is the Chief Financial Officer and an Executive Vice President
of MFS, Mr. Parke is the Chief Equity Officer, Director of Equity Research and
an Executive Vice President of MFS, Mr. Arnold Scott is the Secretary and a
Senior Executive Vice President of MFS and Mr. William Scott is the President of
MFS Fund Distributors, Inc., the distributor of MFS Funds. Messrs. McNeil and
Stewart are the Chairman and the President, respectively, of Sun Life. Sun Life,
a mutual life insurance company, is one of the largest international life
insurance companies and has been operating in the United States since 1895,
establishing a headquarters office here in 1973. The executive officers of MFS
report to the Chairman of Sun Life.
    
 
   
Mr. Shames, the Chairman of MFS, is a Trustee of the Trust. James R. Bordewick,
Jr., Stephen E. Cavan, Geoffrey L. Kurinsky, W. Thomas London, James O. Yost,
Ellen Moynihan and Mark E. Bradley, all of whom are officers of MFS, are
officers of the Trust.
    
 
In certain instances there may be securities which are suitable for the Fund's
portfolios as well as for portfolios of other clients of MFS. Some simultaneous
transactions are inevitable when several clients receive investment advice from
MFS, particularly when the same security is suitable for more then one client.
While in some cases this arrangement could have a detrimental effect on the
price or availability of the security as far as the Fund is concerned, in other
cases, however, it may produce increased investment opportunities for the Fund.
 
                                       14
<PAGE>   62
 
ADMINISTRATOR -- MFS provides the Fund with certain financial, legal,
compliance, shareholder communications and other administrative services
pursuant to a Master Administrative Services Agreement dated March 1, 1997, as
amended. Under this Agreement, the Fund pays MFS an administrative fee of up to
0.015% per annum of the Fund's average daily net assets. This fee reimburses MFS
for a portion of the costs it incurs to provide such services.
 
DISTRIBUTOR -- MFD, a wholly owned subsidiary of the Adviser, is the distributor
of shares of the Fund and also serves as distributor for each of the other MFS
Funds.
 
SHAREHOLDER SERVICING AGENT -- MFS Service Center, Inc. ("Shareholder Servicing
Agent"), a wholly owned subsidiary of MFS, performs transfer agency, certain
dividend disbursing agency and certain other services for the Fund.
 
   
6.  YEAR 2000 ISSUES
    
 
   
The Fund could be adversely affected if the computer systems used by MFS, the
Fund's other service providers or the companies in which the Fund invests do not
properly process date-related information from and after January 1, 2000 (the
"Year 2000 Issue"). MFS recognizes the importance of the Year 2000 Issue and, to
address Year 2000 compliance, created a Year 2000 Program Management Office in
1996, which is separately funded, has a specialized staff and reports directly
to MFS senior management. The Office, with the help of external consultants, is
responsible for ascertaining that all internal systems, data feeds and third
party applications are Year 2000 compliant. While MFS is confident that all MFS
systems will be Year 2000 compliant before the turn of the century, there are
significant systems interdependencies in the domestic and foreign markets for
securities, the business environments in which companies held by the Fund
operate and in MFS' own business environment. MFS has been actively working with
the Fund's other service providers to identify and respond to potential problems
in an effort to ensure Year 2000 compliance or develop contingency plans. Year
2000 compliance is also one of the factors considered by MFS in its ongoing
assessment of companies in which the Fund invests. There can be no assurance,
however, that these steps will be sufficient to avoid any adverse impact on the
Fund.
    
 
   
7.  INFORMATION CONCERNING SHARES OF THE FUND
    
 
PURCHASES
 
Class A and B shares of the Fund may be purchased at the public offering price
through any dealer. As used in the Prospectus and any appendices thereto, the
term "dealer" includes any broker, dealer, bank (including bank trust
departments), registered investment adviser, financial planner and any other
financial institutions having a selling agreement or other similar agreement
with MFD. Dealers may also charge their customers fees relating to investment in
the Fund.
 
This Prospectus offers Class A and B shares, which bear sales charges in
different forms and amounts, as described below:
 
CLASS A SHARES:  Class A shares are generally offered at net asset value plus an
initial sales charge, but in certain cases are offered at net asset value
without an initial sales charge but subject to a CDSC.
 
                                       15
<PAGE>   63
 
PURCHASES SUBJECT TO INITIAL SALES CHARGE. Class A shares are offered at net
asset value plus an initial sales charge as follows:
- --------------------------------------------------------------------------------
 
<TABLE>
<CAPTION>
                                                 SALES CHARGE* AS                 DEALER
                                                  PERCENTAGE OF:              ALLOWANCE AS A
                                            OFFERING       NET AMOUNT          PERCENTAGE OF
          AMOUNT OF PURCHASE                  PRICE         INVESTED          OFFERING PRICE
- -----------------------------------------------------------------------------------------------
<S>                                         <C>            <C>              <C>
Less than $100,000....................        4.75%           4.99%                4.00%
$100,000 but less than $250,000.......        4.00            4.17                 3.20
$250,000 but less than $500,000.......        2.95            3.04                 2.25
$500,000 but less than $1,000,000.....        2.20            2.25                 1.70
$1,000,000 or more....................      None**           None**             See Below**
- -----------------------------------------------------------------------------------------------
</TABLE>
 
 *Because of rounding in the calculation of offering price, actual sales charges
  may be more or less than those calculated using the percentages above.
 
**A CDSC will apply to such purchases, as discussed below.
 
MFD allows discounts to dealers (which are alike for all dealers) from the
applicable public offering price as shown in the above table. In the case of the
maximum sales charge, the dealer retains 4% and MFD retains approximately 3/4 of
1% of the public offering price. The sales charge may vary depending on the
number of shares of the Fund as well as certain other MFS Funds owned or being
purchased, the existence of an agreement to purchase additional shares during a
13-month period (or 36-month period for purchases of $1 million or more) or
other special purchase programs. A description of the Right of Accumulation,
Letter of Intent and Group Purchase privileges by which the sales charge may be
reduced is set forth in the SAI.
 
PURCHASES SUBJECT TO A CDSC (but not an initial sales charge).  In the following
five circumstances, Class A shares are offered at net asset value without an
initial sales charge, but subject to a CDSC equal to 1% of the lesser of the
value of the shares redeemed (exclusive of reinvested dividend and capital gain
distributions) or the total cost of such shares, in the event of a share
redemption within 12 months following the purchase:
 
         (i) on investments of $1 million or more in Class A shares;
 
         (ii) on investments in Class A shares by certain retirement plans
    subject to the Employee Retirement Income Security Act of 1974, as amended
    ("ERISA"), if, prior to July 1, 1996: (a) the plan had established an
    account with the Shareholder Servicing Agent and (b) the sponsoring
    organization had demonstrated to the satisfaction of MFD that either (i) the
    employer had at least 25 employees or (ii) the aggregate purchases by the
    retirement plan of Class A shares of Funds in the MFS Funds would be in an
    aggregate amount of at least $250,000 within a reasonable period of time, as
    determined by MFD in its sole discretion;
 
   
        (iii) on investments in Class A shares by certain retirement plans
    subject to ERISA, if: (a) the retirement plan and/or sponsoring organization
    subscribes to the MFS FUNDamental 401(k) Program or any similar
    recordkeeping system made available by the Shareholder Servicing Agent (the
    "MFS Participant Recordkeeping System"); (b) the plan establishes an account
    with the Shareholder Servicing Agent on or after July 1, 1996; (c) the
    aggregate purchases by the retirement plan of Class A shares of the MFS
    Funds will be in an
    
 
                                       16
<PAGE>   64
 
   
    aggregate amount of at least $500,000 within a reasonable period of time, as
    determined by MFD in its sole discretion; and (d) the plan has not redeemed
    its Class B shares in the MFS Funds in order to purchase Class A shares
    under this category.
    
 
   
          (iv) on investments in Class A shares by certain retirement plans
    subject to ERISA, if: (a) the plan establishes an account with the
    Shareholder Servicing Agent on or after July 1, 1996 and (b) the plan has,
    at the time of purchase, a market value of $500,000 or more invested in
    shares of any class or classes of the MFS Funds; THE RETIREMENT PLAN WILL
    QUALIFY UNDER THIS CATEGORY ONLY IF THE PLAN OR ITS SPONSORING ORGANIZATION
    INFORMS THE SHAREHOLDER SERVICING AGENT PRIOR TO THE PURCHASE THAT THE PLAN
    HAS A MARKET VALUE OF $500,000 OR MORE INVESTED IN SHARES OF ANY CLASS OR
    CLASSES OF THE MFS FUNDS; THE SHAREHOLDER SERVICING AGENT HAS NO OBLIGATION
    INDEPENDENTLY TO DETERMINE WHETHER SUCH A PLAN QUALIFIES UNDER THIS
    CATEGORY; and
    
 
         (v) on investments in Class A shares by certain retirement plans
    subject to ERISA, as amended, if: (a) the plan establishes an account with
    the Shareholder Servicing Agent on or after July 1, 1997; (b) such plan's
    records are maintained on a pooled basis by the Shareholder Servicing Agent;
    and (c) the sponsoring organization demonstrates to the satisfaction of MFD
    that, at the time of purchase, the employer has at least 200 eligible
    employees and the plan has aggregate assets of at least $2,000,000.
 
In the case of all such purchases, MFD will pay commissions to dealers on new
investments in Class A shares made through such dealers as follows:
 
<TABLE>
<CAPTION>
COMMISSION PAID BY MFD TO DEALERS        CUMULATIVE PURCHASE AMOUNT
- ---------------------------------   ------------------------------------
<C>                                 <S>
              1.00%                 On the first $2,000,000, plus
              0.80%                 Over $2,000,000 to $3,000,000, plus
              0.50%                 Over $3,000,000 to $50,000,000, plus
              0.25%                 Over $50,000,000
</TABLE>
 
   
For purposes of determining the level of commissions to be paid to dealers with
respect to a shareholder's new investment in Class A purchases for each
shareholder account (and certain other accounts for which the shareholder is a
record or beneficial holder) will be aggregated over a 12-month period
(commencing from the date of the first such purchases).
    
 
See "Redemptions and Repurchases -- Contingent Deferred Sales Charge" in the
Prospectus for further discussion of the CDSC.
 
WAIVERS OF INITIAL SALES CHARGE AND CDSC.  In certain circumstances, the initial
sales charged imposed upon purchases of Class A shares and the CDSC imposed upon
redemption of Class A shares is waived. These circumstances are described in
Appendix A to this Prospectus. In addition to these circumstances, the CDSC
imposed upon the redemption of Class A shares is waived with respect to shares
held by certain retirement plans qualified under Section 401(a) or 403(b) of the
Internal Revenue Code of 1986, as amended (the "Code"), and subject to ERISA,
where:
 
 (i) the retirement plan and/or sponsoring organization does not subscribe to
     the MFS Participant Recordkeeping System; and
 
                                       17
<PAGE>   65
 
(ii) the retirement plan and/or sponsoring organization demonstrates to the
     satisfaction of, and certifies to, the Shareholder Servicing Agent that the
     retirement plan has, at the time of certification or will have pursuant to
     a purchase order placed with the certification, a market value of $500,000
     or more invested in shares of any class or classes of the MFS Funds and
     aggregate assets of at least $10 million;
 
provided, however, that the CDSC will not be waived (i.e., it will be imposed)
(a) with respect to plans which establish an account with the Shareholder
Servicing Agent on or after November 1, 1997, in the event that the plan makes a
complete redemption of all of its shares in the MFS Funds, or (b) with respect
to plans which established an account with the Shareholder Servicing Agent prior
to November 1, 1997, in the event that there is a change in law or regulations
which results in a material adverse change to the tax advantaged nature of the
plan, or in the event that the plan and/or sponsoring organization: (i) becomes
insolvent or bankrupt; (ii) is terminated under ERISA or is liquidated or
dissolved; or (iii) is acquired by, merged into, or consolidated with, any other
entity.
 
CLASS B SHARES: Class B shares are offered at net asset value without an initial
sales charge but subject to a CDSC upon redemption as follows:
 
<TABLE>
<CAPTION>
         YEAR OF                  CONTINGENT
        REDEMPTION              DEFERRED SALES
      AFTER PURCHASE                CHARGE
      --------------            --------------
<S>                             <C>
First.....................             4%
Second....................             4%
Third.....................             3%
Fourth....................             3%
Fifth.....................             2%
Sixth.....................             1%
Seventh and following.....             0%
</TABLE>
 
The CDSC imposed is assessed against the lesser of the value of the shares
redeemed (exclusive of reinvested dividends and capital gain distributions) or
the total cost of such shares. No CDSC is assessed against shares acquired
through the automatic reinvestment of dividends or capital gain distributions.
 
Except as described below, MFD will pay commissions to dealers of 3.75% of the
purchase price of Class B shares purchased through dealers. MFD will also
advance to dealers the first year service fee payable under the Distribution
Plan (see "Class B Distribution Plan" below) at a rate equal to 0.25% of the
purchase price of such shares. Therefore, the total amount paid to a dealer upon
the sale of Class B shares is 4% of the purchase price of the shares (commission
rate of 3.75% plus a service fee equal to 0.25% of the purchase price).
 
   
Class B shares purchased by a retirement plan whose sponsoring organization
subscribes to the MFS Participant Recordkeeping System and which has established
its account with the Shareholder Servicing Agent between July 1, 1996 and
December 31, 1998, will be subject to the CDSC described above, only under
limited circumstances, as explained below under "Waivers of CDSC." With respect
to such purchases, MFD pays an amount to dealers equal to 3.00% of the amount
purchased through such dealers (rather than the 4.00% payment described above),
    
 
                                       18
<PAGE>   66
 
which is comprised of a commission of 2.75% plus the advancement of the first
year service fee equal to 0.25% of the purchase price payable under the
Distribution Plan.
 
   
For purchases of Class B shares by a retirement plan whose sponsoring
organization subscribes to the MFS Recordkeeper Plus product and which
establishes its account with MFSC on or after January 1, 1999 (provided that the
plan establishment paperwork is received by MFSC in good order on or after
November 15, 1998), MFD pays no up front commissions to dealers, but instead
pays an amount to dealers equal to 1% per annum of the average daily net assets
of the Fund attributable to plan assets, payable at the rate of 0.25% at the end
of each calendar quarter, in arrears. This commission structure is not available
with respect to a plan with a pre-existing account(s) with any MFS Fund which
seeks to switch to the MFS Recordkeeper Plus Product.
    
 
   
Certain retirement plans are eligible to purchase Class A shares of the Fund at
net asset value without an initial sales charge but subject to a 1% CDSC if the
plan has, at the time of purchase, a market value of $500,000 or more invested
in shares of any class or classes of the MFS Funds. IN THIS EVENT, THE PLAN OR
ITS SPONSORING ORGANIZATION SHOULD INFORM THE SHAREHOLDER SERVICING AGENT THAT
THE PLAN IS ELIGIBLE TO PURCHASE CLASS A SHARES UNDER THIS CATEGORY; THE
SHAREHOLDER SERVICING AGENT HAS NO OBLIGATION INDEPENDENTLY TO DETERMINE WHETHER
SUCH A PLAN QUALIFIES UNDER THIS CATEGORY FOR THE PURCHASE OF CLASS A SHARES.
    
 
See "Redemptions and Repurchases -- Contingent Deferred Sales Charge" for
further discussion of the CDSC.
 
   
WAIVERS OF CDSC.  In certain circumstances, the CDSC imposed upon redemption of
Class B shares is waived. These circumstances are described in Appendix A to
this Prospectus. In addition to these circumstances, the CDSC imposed upon the
redemption of Class B shares is waived with respect to shares held by a
retirement plan whose sponsoring organization subscribes to the MFS Participant
Recordkeeping System and which established an account with the Shareholder
Servicing Agent between July 1, 1996 and December 31, 1998; provided, however,
that the CDSC will not be waived (i.e., it will be imposed) in the event that
there is a change in law or regulations which results in a material adverse
change to the tax advantaged nature of the plan, or in the event that the plan
and/or sponsoring organization: (i) becomes insolvent or bankrupt; (ii) is
terminated under ERISA or is liquidated or dissolved; or (iii) is acquired by,
merged into, or consolidated with, any other entity.
    
 
   
In addition to these circumstances, the CDSC imposed upon the redemption of
Class B shares is waived with respect to shares held by a retirement plan whose
sponsoring organization subscribes to the MFS Recordkeeper Plus product and
which establishes its account with MFSC on or after January 1, 1999 (provided
that the plan establishment paperwork is received by MFSC in good order on or
after November 15, 1998). A plan with a pre-existing account(s) with any MFS
Fund which switches to the MFS Recordkeeper Plus product will not become
eligible for this waiver category.
    
 
CONVERSION OF CLASS B SHARES.  Class B shares of the Fund that remain
outstanding for approximately eight years will convert to Class A shares of the
same Fund. Shares purchased through the reinvestment of distributions paid in
respect of Class B shares will be treated as Class B shares for purposes of the
payment of the distribution and service fees under the Distribution Plan. See
"Distribution Plan" below. However, for purposes of conversion to Class A
                                       19
<PAGE>   67
 
shares, all shares in a shareholder's account that were purchased through the
reinvestment of dividends and distributions paid in respect of Class B shares
(and which have not converted to Class A shares as provided in the following
sentence) will be held in a separate sub-account. Each time any Class B shares
in the shareholder's account (other than those in the sub-account) convert to
Class A shares, a portion of the Class B shares then in the sub-account will
also convert to Class A shares. The portion will be determined by the ratio that
the shareholder's Class B shares not acquired through reinvestment of dividends
and distributions that are converting to Class A shares bear to the
shareholder's total Class B shares not acquired through reinvestment. The
conversion of Class B shares to Class A shares is subject to the continuing
availability of a ruling from the Internal Revenue Service or an opinion of
counsel that such conversion will not constitute a taxable event for federal tax
purposes. There can be no assurance that such ruling or opinion will be
available, and the conversion of Class B shares to Class A shares will not occur
if such ruling or opinion is not available. In such event, Class B shares would
continue to be subject to higher expenses than Class A shares for an indefinite
period.
 
GENERAL:  The following information applies to purchases of all classes of the
Fund's shares.
 
MINIMUM INVESTMENT.  Except as described below, the minimum initial investment
is $1,000 per account and the minimum additional investment is $50 per account.
Accounts being established for monthly automatic investments and under payroll
savings programs and tax-deferred retirement programs (other than IRA's)
involving the submission of investments by means of group remittal statements
are subject to a $50 minimum on initial and additional investments per account.
The minimum initial investment for IRAs is $250 per account and the minimum
additional investment is $50 per account. Accounts being established for
participation in the Automatic Exchange Plan are subject to a $50 minimum on
initial and additional investments per account. There are also other limited
exceptions to these minimums for certain tax-deferred retirement programs. Any
minimums may be changed at any time at the discretion of MFD. The Fund reserves
the right to cease offering its shares for sale at any time.
 
SUBSEQUENT INVESTMENT BY TELEPHONE:  Each shareholder may purchase additional
shares of any MFS Fund by telephoning the Shareholder Servicing Agent toll-free
at (800) 225-2606. The minimum purchase amount is $50 and the maximum purchase
amount is $100,000. Shareholders wishing to avail themselves of this telephone
purchase privilege must so elect on their Account Application and designate
thereon a bank and account number from which purchases will be made. If a
telephone purchase request is received by the Shareholder Servicing Agent on any
business day prior to the close of regular trading on the Exchange (generally,
4:00 p.m., Eastern time), the purchase will occur at the closing net asset value
of the shares purchased on that day. The Shareholder Servicing Agent may be
liable for any losses resulting from unauthorized telephone transactions if it
does not follow reasonable procedures designed to verify the identity of the
caller. The Shareholder Servicing Agent will request personal or other
information from the caller, and will normally also record calls. Shareholders
should verify the accuracy of confirmation statements immediately after their
receipt.
 
   
RIGHT TO REJECT PURCHASE ORDERS/MARKET TIMING.  Purchases and exchanges should
be made for investment purposes only. The Fund and MFD each reserve the right to
reject or restrict any specific purchase or exchange request. Because an
exchange request involves both a request to
    
                                       20
<PAGE>   68
 
   
redeem shares of one fund and to purchase shares of another fund, the Fund
considers the underlying redemption request conditioned upon the acceptance of
the underlying purchase request. Therefore, in the event that the Fund or MFD
rejects an exchange request, neither the redemption nor the purchase side of the
exchange will be processed.
    
 
   
The MFS Family of Funds is not designed for professional market timing
organizations or other entities using programmed or frequent exchanges. The MFS
Family of Funds defines a "market timer" as an individual or organization acting
on behalf of one or more individuals, if (i) the individual or organization
makes six or more exchange requests among the MFS Family of Funds or three or
more exchange requests out of any of the MFS high yield bond funds or MFS
municipal bond funds per calendar year and (ii) any one of such exchange
requests represents shares equal in value to $1 million or more. Accounts under
common ownership or control, including accounts administered by market timers,
will be aggregated for purposes of this definition.
    
 
   
As noted above, the Fund and MFD each reserves the right to reject or restrict
any specific purchase and exchange request and, in addition, may impose specific
limitations with respect to market timers, including (i) delaying for up to
seven days the purchase side of an exchange request by market timers, (ii)
rejecting or otherwise restricting purchase or exchange requests by market
timers; and (iii) permitting exchanges by market timers only into certain MFS
Funds.
    
 
DEALER CONCESSIONS.  Dealers may receive different compensation with respect to
sales of Class A and Class B shares. In addition, from time to time, MFD may pay
dealers 100% of the applicable sales charge on sales of Class A shares of
certain specified MFS Funds sold by such dealer during a specified sales period.
In addition, MFD or its affiliates may, from time to time, pay dealers an
additional commission equal to 0.50% of the net asset value of all of the Class
B shares of certain specified MFS Funds sold by such dealer during a specified
sales period. In addition, from time to time, MFD, at its expense, may provide
additional commissions, compensation or promotional incentives ("concessions")
to dealers which sell or arrange for the sale of shares of the Fund. Such
concessions provided by MFD may include financial assistance to dealers in
connection with preapproved conferences or seminars, sales or training programs
for invited registered representatives and other employees, payment for travel
expenses, including lodging, incurred by registered representatives and other
employees for such seminars or training programs, seminars for the public,
advertising and sales campaigns regarding one or more MFS Funds, and/or other
dealer-sponsored events. From time to time, MFD may make expense reimbursements
for special training of a dealer's registered representatives and other
employees in group meetings or to help pay the expenses of sales contests. Other
concessions may be offered to the extent not prohibited by state laws or any
self-regulatory agency, such as the NASD.
 
SPECIAL INVESTMENT PROGRAMS.  For shareholders who elect to participate in
certain investment programs (e.g., the Automatic Investment Plan) or other
shareholder services, MFD or its affiliates may either (i) give a gift of
nominal value, such as a hand-held calculator or (ii) make a nominal charitable
contribution on their behalf.
 
RESTRICTIONS ON ACTIVITIES OF NATIONAL BANKS.  The Glass-Steagall Act prohibits
national banks from engaging in the business of underwriting, selling or
distributing securities. Although the
 
                                       21
<PAGE>   69
 
scope of the prohibition has not been clearly defined, MFD believes that such
Act should not preclude banks from entering into agency agreements with MFD. If,
however, a bank were prohibited from so acting, the Trustees would consider what
actions, if any, would be necessary to continue to provide efficient and
effective shareholder services in respect of shareholders who invested in the
Fund through a national bank. It is not expected that shareholders would suffer
any adverse financial consequence as a result of these occurrences. In addition,
state securities laws on this issue may differ from the interpretation of
federal law expressed herein and banks and financial institutions may be
required to register as broker-dealers pursuant to state law.
                            ------------------------
 
A shareholder whose shares are held in the name of, or controlled by, a dealer
might not receive many of the privileges and services from the Fund (such as
Right of Accumulation, Letter of Intent and certain recordkeeping services) that
the Fund ordinarily provides.
 
EXCHANGES
 
Subject to the requirements set forth below, some or all of the shares in an
account with the Fund for which payment has been received by the Fund (i.e., an
established account) may be exchanged for shares of the same class of any of the
other MFS Funds at net asset value (if available for sale). Shares of one class
may not be exchanged for shares of any other class.
 
EXCHANGES AMONG MFS FUNDS (EXCLUDING EXCHANGES FROM MFS MONEY MARKET FUNDS):  No
initial sales charges or CDSC will be imposed in connection with an exchange
from shares of an MFS Fund to shares of any other MFS Fund, except with respect
to exchanges from an MFS money market fund to another MFS Fund which is not an
MFS money market fund (discussed below). With respect to an exchange involving
shares subject to a CDSC, the CDSC will be unaffected by the exchange and the
holding period for purposes of calculating the CDSC will carry over to the
acquired shares.
 
EXCHANGES FROM AN MFS MONEY MARKET FUND:  Special rules apply with respect to
the imposition of an initial sales charge or a CDSC for exchanges from an MFS
money market fund to another MFS Fund which is not an MFS money market fund.
These rules are described under the caption "Exchanges" in the Prospectuses of
those MFS money market funds.
 
EXCHANGES INVOLVING THE MFS FIXED FUND:  Class A shares of any MFS Fund held by
certain qualified retirement plans may be exchanged for units of participation
of the MFS Fixed Fund (a bank collective investment fund) (the "Units"), and
Units may be exchanged for Class A shares of any MFS Fund. With respect to
exchanges between Class A shares subject to a CDSC and Units, the CDSC will
carry over to the acquired shares or Units and will be deducted from the
redemption proceeds when such shares or Units are subsequently redeemed,
assuming the CDSC is then payable (the period during which the Class A shares
and the Units were held will be aggregated for purposes of calculating the
applicable CDSC). In the event that a shareholder initially purchases Units and
then exchanges into Class A shares subject to an initial sales charge of an MFS
Fund, the initial sales charge shall be due upon such exchange, but will not be
imposed with respect to any subsequent exchanges between such Class A shares and
Units with respect to shares on which the initial sales charge has already been
paid. In the event that a shareholder initially purchases Units and then
exchanges into Class A shares subject to a CDSC of an MFS Fund, the CDSC period
will commence upon such exchange, and the applicability of
 
                                       22
<PAGE>   70
 
the CDSC with respect to subsequent exchanges shall be governed by the rules set
forth above in this paragraph.
 
GENERAL:  A shareholder should read the prospectus of the other MFS Fund into
which an exchange is made and consider the differences in objectives, policies
and restrictions before making any exchange. Exchanges will be made only after
instructions in writing or by telephone (an "Exchange Request") are received for
an established account by the Shareholder Servicing Agent in proper form (i.e.,
if in writing -- signed by the record owner(s) exactly as the shares are
registered; if by telephone -- proper account identification is given by the
dealer or shareholder of record) and each exchange must involve either shares
having an aggregate value of at least $1,000 ($50 in case of retirement plan
participants whose sponsoring organizations subscribe to the MFS FUNDamental
401(k) Plan or another similar 401(k) recordkeeping system made available by the
Shareholder Servicing Agent) or all the shares in the account. If an Exchange
Request is received by the Shareholder Servicing Agent on any business day prior
to the close of regular trading on the Exchange (generally, 4:00 p.m., Eastern
time), the exchange will occur on that day if all the requirements set forth
above have been complied with at that time and subject to the Fund's right to
reject purchase orders. No more than five exchanges may be made in any one
Exchange Request by telephone. Additional information concerning this exchange
privilege and prospectuses for any of the other MFS Funds may be obtained from
dealers or the Shareholder Servicing Agent. For federal and (generally) state
income tax purposes, and exchange is treated as a sale of the shares exchanged
and, therefore, an exchange could result in a gain or loss to the shareholder
making the exchange. Exchanges by telephone are automatically available to most
non-retirement plan accounts and certain retirement plan accounts. For further
information regarding exchanges by telephone, see "Redemptions by Telephone."
The exchange privilege (or any aspect of it) may be changed or discontinued and
is subject to certain limitations, including certain restrictions on purchases
by market timers.
 
REDEMPTIONS AND REPURCHASES
 
A shareholder may withdraw all or any portion of the value of his account on any
date on which the Fund is open for business by redeeming shares at their net
asset value (a redemption ) or by selling such shares to the Fund through a
dealer (a repurchase). Certain redemptions and repurchases are, however, subject
to a CDSC. See "Contingent Deferred Sales Charge" below. Because the net asset
value of shares of the account fluctuates, redemptions or repurchases, which are
taxable transactions, are likely to result in gains or losses to the
shareholder. When a shareholder withdraws an amount from his account, the
shareholder is deemed to have tendered for redemption a sufficient number of
full and fractional shares in his account to cover the amount withdrawn. The
proceeds of a redemption or repurchase will normally be available within seven
days, except for shares purchased or received in exchange for shares purchased
by check (including certified checks or cashier's checks). Payment of redemption
proceeds may be delayed for up to 15 days from the purchase date in an effort to
assure that such check has cleared.
 
REDEMPTION BY MAIL:  Each shareholder may redeem all or any portion of the
shares in his account by mailing or delivering to the Shareholder Servicing
Agent (see back cover for address) a stock power with a written request for
redemption or letter of instruction, together with his share certificates (if
any were issued), all in "good order" for transfer. "Good order" generally
 
                                       23
<PAGE>   71
 
means that the stock power, written request for redemption, letter of
instruction or certificate must be endorsed by the record owner(s) exactly as
the shares are registered and the signature(s) must be guaranteed in the manner
set forth below under the caption "Signature Guarantee." In addition, in some
cases "good order" will require the furnishing of additional documents. The
Shareholder Servicing Agent may make certain de minimis exceptions to the above
requirements for redemption. Within seven days after receipt of a redemption
request in "good order" by the Shareholder Servicing Agent, the Fund will make
payment in cash of the net asset value of the shares next determined after such
redemption request was received, reduced by the amount of any applicable CDSC
described above and the amount of any income tax required to be withheld, except
during any period in which the right of redemption is suspended or date of
payment is postponed because the Exchange is closed or trading on such Exchange
is restricted or to the extent otherwise permitted by the 1940 Act if an
emergency exists. See "Tax Status" below.
 
REDEMPTION BY TELEPHONE:  Each shareholder may redeem an amount from his account
by telephoning the Shareholder Servicing Agent toll-free at (800) 225-2606.
Shareholders wishing to avail themselves of this telephone redemption privilege
must so elect on their Account Application, designate thereon a bank and account
number to receive the proceeds of such redemption, and sign the Account
Application Form with the signature(s) guaranteed in the manner set forth below
under the caption "Signature Guarantee." The proceeds of such a redemption,
reduced by the amount of any applicable CDSC and the amount of any income tax
required to be withheld, are mailed by check to the designated account, without
charge, if the redemption proceeds do not exceed $1,000, and are wired in
federal funds to the designated account if the redemption proceeds exceed
$1,000. If a telephone redemption request is received by the Shareholder
Servicing Agent by the close of regular trading on the Exchange on any business
day, shares will be redeemed at the closing net asset value of the Fund on that
day. Subject to the conditions described in this section, proceeds of a
redemption are normally mailed or wired on the next business day following the
date of receipt of the order for redemption. The Shareholder Servicing Agent may
be liable for any losses resulting from unauthorized telephone transactions if
it does not follow reasonable procedures designed to verify the identity of the
caller. The Shareholder Servicing Agent will request personal or other
information from the caller, and will normally also record calls. Shareholders
should verify the accuracy of confirmation statements immediately after their
receipt.
 
REPURCHASE THROUGH A DEALER:  If a shareholder desires to sell his shares
through his dealer (a repurchase), the shareholder can place a repurchase order
with his dealer, who may charge the shareholder a fee. IF THE DEALER RECEIVES
THE SHAREHOLDER'S ORDER PRIOR TO THE CLOSE OF REGULAR TRADING ON THE EXCHANGE
AND COMMUNICATES IT TO MFD BEFORE THE CLOSE OF BUSINESS ON THE SAME DAY, THE
SHAREHOLDER WILL RECEIVE THE NET ASSET VALUE CALCULATED ON THAT DAY, REDUCED BY
THE AMOUNT OF ANY APPLICABLE CDSC AND THE AMOUNT OF ANY INCOME TAX REQUIRED TO
BE WITHHELD.
 
REDEMPTION BY CHECK:  Only Class A shares may be redeemed by check. A
shareholder owning Class A shares of the Fund may elect to have a special
account with State Street Bank and Trust Company (the "Bank") for the purpose of
redeeming Class A shares from his or her account by check. The Bank will provide
each Class A shareholder, upon request, with forms of checks
 
                                       24
<PAGE>   72
 
drawn on the Bank. Only shareholders having accounts in which no share
certificates have been issued will be permitted to redeem shares by check.
Checks may be made payable in any amount not less than $500. Shareholders
wishing to avail themselves of this redemption by check privilege should so
request on their Account Application, must execute signature cards (for
additional information, see the Account Application) with signature guaranteed
in the manner set forth under the caption "Signature Guarantee" below, and must
return any Class A share certificates issued to them. Additional documentation
will be required from corporations, partnerships, fiduciaries or other such
institutional investors. All checks must be signed by the shareholder(s) of
record exactly as the account is registered before the Bank will honor them. The
shareholders of joint accounts may authorize each shareholder to redeem by
check. The check may not draw on monthly dividends which have been declared but
not distributed. SHAREHOLDERS WHO PURCHASE CLASS A SHARES BY CHECK (INCLUDING
CERTIFIED CHECKS OR CASHIERS' CHECKS) MAY WRITE CHECKS AGAINST THOSE SHARES ONLY
AFTER THEY HAVE BEEN ON THE FUND'S BOOKS FOR 15 DAYS. WHEN SUCH A CHECK IS
PRESENTED TO THE BANK FOR PAYMENT, A SUFFICIENT NUMBER OF FULL AND FRACTIONAL
SHARES WILL BE REDEEMED TO COVER THE AMOUNT OF THE CHECK, ANY APPLICABLE CDSC
AND THE AMOUNT OF ANY INCOME TAX REQUIRED TO BE WITHHELD. IF THE AMOUNT OF THE
CHECK, PLUS ANY APPLICABLE CDSC AND THE AMOUNT OF ANY INCOME TAX REQUIRED TO BE
WITHHELD IS GREATER THAN THE VALUE OF CLASS A SHARES HELD IN THE SHAREHOLDERS'
ACCOUNT, THE CHECK WILL BE RETURNED UNPAID, AND THE SHAREHOLDER MAY BE SUBJECT
TO EXTRA CHARGES. TO AVOID DISHONOR OF CHECKS DUE TO FLUCTUATIONS IN ACCOUNT
VALUE, SHAREHOLDERS ARE ADVISED AGAINST REDEEMING ALL OR MOST OF THEIR ACCOUNT
BY CHECK. CHECKS SHOULD NOT BE USED TO CLOSE A FUND ACCOUNT BECAUSE WHEN THE
CHECK IS WRITTEN, THE SHAREHOLDER WILL NOT KNOW THE EXACT TOTAL VALUE OF THE
ACCOUNT ON THE DAY THE CHECK CLEARS. There is presently no charge to the
shareholder for the maintenance of this special account or for the clearance of
any checks, but the Fund and the Bank reserve the right to impose such charges
or to modify or terminate the redemption by check privilege at any time.
 
CONTINGENT DEFERRED SALES CHARGE:  Investments in Class A or Class B shares
("Direct Purchases") will be subject to a CDSC for a period of 12 months
(however, the CDSC on Class A shares is only imposed with respect to purchases
of $1 million or more of Class A shares or purchases by certain retirement plans
of Class A shares); or (ii) with respect to Class B shares, six years. Purchases
of Class A shares made during a calendar month, regardless of when during the
month the investment occurred, will age one month on the last day of the month
and each subsequent month. Class B shares purchased on or after January 1, 1993
will be aggregated on a calendar month basis -- all transactions made during a
calendar month, regardless of when during the month they have occurred, will age
one year at the close of business on the last day of such month in the following
calendar year and each subsequent year. For Class B shares of the Fund purchased
prior to January 1, 1993, transactions will be aggregated on a calendar year
basis -- all transactions made during a calendar year, regardless of when during
the year they have occurred, will age one year at the close of business on
December 31 of that year and each subsequent year.
 
At the time of a redemption, the amount by which the value of a shareholder's
account for a particular class of shares represented by Direct Purchases exceeds
the sum of the six calendar year aggregations (12 months in the case of
purchases of $1 million or more of Class A shares or purchases by certain
retirement plans of Class A shares) of Direct Purchases may be
                                       25
<PAGE>   73
 
redeemed without charge ("Free Amount"). Moreover, no CDSC is ever assessed on
additional shares acquired through the automatic reinvestment of dividends or
capital gain distributions ("Reinvested Shares"). Therefore, at the time of
redemption of a particular class, (i) any Free Amount is not subject to the
CDSC, and (ii) the amount of redemption equal to the then-current value of
Reinvested Shares is not subject to the CDSC, but (iii) any amount of the
redemption in excess of the aggregate of the then-current value of Reinvested
Shares and the Free Amount is subject to a CDSC. The CDSC will first be applied
against the amount of Direct Purchases which will result in any such charge
being imposed at the lowest possible rate. The CDSC to be imposed upon
redemptions will be calculated as set forth in "Purchases" above.
 
The applicability of a CDSC will be unaffected by exchanges or transfers of
registration, except as described in Appendix A hereto.
 
GENERAL:  The following information applies to redemptions and repurchases of
all classes of the Fund's shares.
 
SIGNATURE GUARANTEE.  In order to protect shareholders against fraud, the Fund
requires, in certain instances as indicated above, that the shareholder's
signature be guaranteed. In these cases the shareholder's signature must be
guaranteed by an eligible bank, broker, dealer, credit union, national
securities exchange, registered securities association, clearing agency or
savings association. Signature guarantees shall be accepted in accordance with
policies established by the Shareholder Servicing Agent.
 
REINSTATEMENT PRIVILEGE.  Shareholders of the Fund who have redeemed their
shares have a one-time right to reinvest the redemption proceeds in the same
class of shares of any of the MFS Funds (if shares of such Fund are available
for sale) at net asset value (with a credit for any CDSC paid) within 90 days of
the redemption pursuant to the Reinstatement Privilege. If the shares credited
for any CDSC paid are then redeemed within six years of the initial purchase in
the case of Class B shares or within 12 months of the initial purchase for
certain Class A share purchases, a CDSC will be imposed upon redemption. Such
purchases under the Reinstatement Privilege are subject to all limitations in
the SAI regarding this privilege.
 
IN-KIND DISTRIBUTIONS.  The Trust agrees to redeem shares of the Fund solely in
cash up to the lesser of $250,000 or 1% of the net asset value of the Fund
during any 90-day period for any one shareholder. The Fund has reserved the
right to pay other redemptions or repurchase price of shares of the Fund, either
totally or partially, by a distribution in-kind of securities (instead of cash)
from the Fund's portfolio. The securities distributed in such a distribution
would be valued at the same amount as that assigned to them in calculating the
net asset value for the shares being sold. If a shareholder received a
distribution in-kind, the shareholder could incur brokerage or transaction
charges when converting the securities to cash.
 
INVOLUNTARY REDEMPTIONS/SMALL ACCOUNTS.  Due to the relatively high cost of
maintaining small accounts, the Fund reserves the right to redeem shares in any
account for their then-current value if at any time the total investment in such
account drops below $500 because of redemptions or exchanges, except in the case
of accounts being established for monthly automatic investments and certain
payroll savings programs, Automatic Exchange Plan accounts and tax-deferred
retirement plans, for which there is a lower minimum investment requirement. See
"Purchases -- General -- Minimum Investment." Shareholders will be notified that
the
                                       26
<PAGE>   74
 
value of their account is less than the minimum investment requirement and
allowed 60 days to make an additional investment before the redemption is
processed.
 
DISTRIBUTION PLAN
 
The Trustees have adopted a Distribution Plan for Class B shares pursuant to
Section 12(b) of the 1940 Act and Rule 12b-1 thereunder (the "Distribution
Plan"), after having concluded that there is a reasonable likelihood that the
Distribution Plan would benefit the Fund and its Class B shareholders.
 
In certain circumstances, the fees described below may not be imposed or are
being waived. These circumstances, if any, are described below under the heading
"Current Level of Distribution and Service Fees."
 
SERVICE FEE.  The Distribution Plan provides that the Fund may pay MFD a service
fee of up to 0.25% of the average daily net assets attributable to Class B
shares annually in order that MFD may pay expenses on behalf of the Fund
relating to the servicing of Class B shares. The service fee is used by MFD to
compensate dealers which enter into a sales agreement with MFD in consideration
for all personal services and/or account maintenance services rendered by the
dealer with respect to Class B shares owned by investors for whom such dealer is
the dealer or holder of record. MFD may from time to time reduce the amount of
the service fees paid for shares sold prior to a certain date. Service fees may
be reduced for a dealer that is the holder or dealer of record for an investor
who owns shares of the Fund having an aggregate net asset value at or above a
certain dollar level. Dealers may from time to time be required to meet certain
criteria in order to receive service fees. MFD or its affiliates are entitled to
retain all service fees payable under the Distribution Plan for which there is
no dealer of record or for which qualification standards have not been met as
partial consideration for personal services and/or account maintenance services
performed by MFD or its affiliates to shareholder accounts.
 
Class B shares are offered at net asset value without an initial sales charge
but subject to a CDSC. See "Purchases -- Class B Shares" above. MFD will advance
to dealers the first year service fee described above at a rate equal to 0.25%
of the purchase price of such shares and, as compensation therefor, MFD may
retain the service fee paid by the Fund with respect to such shares for the
first year after purchase. Dealers will become eligible to receive the ongoing
0.25% per annum service fee with respect to such shares commencing in the
thirteenth month following purchase.
 
DISTRIBUTION FEE.  The Distribution Plan provides that the Fund may pay MFD a
distribution fee equal, on an annual basis, to 0.75% of the Fund's average daily
net assets attributable to the Class B shares as partial consideration for
distribution services performed and expenses incurred in the performance of
MFD's obligations under its distribution agreement with the Fund (including the
3.75% commission it pays to dealers upon purchase of Class B shares, as
described under "Purchases -- Class B Shares" above). See "Management of the
Fund -- Distributor" in the SAI. While the amount of compensation received by
MFD in the form of distribution fees during any year may be more or less than
the expense incurred by MFD under its distribution agreement with the Fund, the
Fund is not liable to MFD for any losses MFD may incur in performing services
under its distribution agreement with the Fund.
 
                                       27
<PAGE>   75
 
OTHER FEATURES.  Fees payable under the Distribution Plan are charged to, and
therefore reduce, income allocated to the Class B shares.
 
   
CURRENT LEVEL OF DISTRIBUTION AND SERVICE FEES.  The Fund's Class B distribution
and service fees for its current fiscal year are 0.80% per annum of the average
net assets. Except in the case of the 0.25% per annum Class B service fee paid
by the Fund upon the sale of Class B shares, payment of the Class B service fee
will be suspended until such date as the Trustees of the Trust may determine.
    
 
DISTRIBUTIONS
 
The Fund intends to declare daily and pay to its shareholders substantially all
of its net investment income as dividends on a monthly basis. Dividends are
generally distributed on the first business day of the following month. In
addition, the Fund may make one or more distributions during the calendar year
to its shareholders from any long-term capital gains and may also make one or
more distributions during the calendar year to its shareholders from short-term
capital gains. Shareholders may elect to receive dividends and capital gain
distributions in either cash or additional shares of the same class with respect
to which a distribution is made (see "Tax Status" and "Shareholder Services --
Distribution Options" below). Distributions paid by the Fund with respect to
Class A shares will generally be greater than those paid with respect to Class B
shares because expenses attributable to Class B shares will generally be higher.
 
TAX STATUS
 
   
The Fund is treated as an entity separate from the other series of the Trust for
federal income tax purposes. In order to minimize the taxes the Fund would
otherwise be required to pay, the Fund intends to qualify each year as a
"regulated investment company" under Subchapter M of the Internal Revenue Code
of 1986, as amended (the "Code"). Because the Fund intends to distribute all of
its net investment income and net realized capital gains to its shareholders in
accordance with the timing requirements imposed by the Code, it is not expected
that the Fund will be required to pay entity level federal income or excise
taxes.
    
 
   
The Fund expects that dividends paid to shareholders from interest on Municipal
Obligations will be exempt from federal income tax because the Fund intends to
satisfy certain requirements of the Code. One such requirement is that at the
close of each quarter of its taxable year, at least 50% of the value of the
Fund's total assets consists of obligations whose interest is exempt from
federal income tax. Distributions of income from capital gains, from investments
in taxable securities, and from certain other transactions including options and
futures transactions will be taxable to shareholders, whether the distribution
is paid in cash or reinvested in additional shares.
    
 
   
Interest on indebtedness incurred by shareholders to purchase or carry shares of
the Fund will not be deductible for federal income tax purposes. Exempt-interest
dividends are taken into account in calculating the amount of social security
and railroad retirement benefits that may be subject to federal income tax, and
certain distributions of exempt-interest dividends may be a tax preference item
for purposes of the federal individual and corporate alternative minimum tax.
All
    
 
                                       28
<PAGE>   76
 
   
exempt interest dividends may affect a corporate shareholder's alternative
minimum tax liability. Depending on the nature of the distribution and the
residence of the shareholder, certain Fund distributions may be subject to state
and local income taxes. Entities or persons who are "substantial users" (or
persons related to "substantial users") of facilities financed by private
activity bonds should consult their tax advisers before purchasing shares of the
Fund.
    
 
   
Shortly after the end of each calendar year, each shareholder will be sent a
statement setting forth the federal income tax status of all dividends and
distributions for that year, including the portion exempt from federal income
taxes as "exempt-interest dividends," the portion, if any, that is a tax
preference item under the federal alternative minimum tax, the portion, if any,
taxable as ordinary income, the portion, if any, taxable as long-term capital
gain (as well as the rate category or categories under which such gain is
taxable), the portion, if any, representing a return of capital (which is
generally free of current taxes but which results in a basis reduction), and the
amount, if any, of federal income tax withheld.
    
 
   
Fund distributions of net capital gains or net short-term capital gains will
reduce the Fund's net asset value per share. Shareholders who buy shares shortly
before the Fund makes such a distribution may thus pay the full price for the
shares and then effectively receive a portion of the purchase price back as a
taxable distribution.
    
 
The Fund intends to withhold U.S. federal income tax at the rate of 30% (or any
lower rate permitted under an applicable treaty) on taxable dividends and other
payments that are subject to such withholding and that are made to persons who
are neither citizens nor residents of the U.S. The Fund is also required in
certain circumstances to apply backup withholding at the rate of 31% on taxable
dividends and redemption proceeds paid to any shareholder (including a
shareholder who is neither a citizen nor a resident of the U.S.) who does not
furnish to the Fund certain information and certifications or who is otherwise
subject to backup withholding. Backup withholding will not, however, be applied
to payments that have been subject to 30% withholding. Prospective investors
should read the Fund's Account Application for additional information regarding
backup withholding of federal income tax and should consult their own tax
advisers as to the tax consequences to them of an investment in the Fund.
 
NET ASSET VALUE
 
   
The net asset value per share of each class of the Fund is determined each day
during which the Exchange is open for trading. This determination is made once
during each such day as of the close of regular trading on the Exchange by
deducting the amount of the liabilities attributable to the class from the value
of the Fund's assets attributable to the class and dividing the difference by
the number of shares of the class outstanding. Assets in the Fund's portfolio
are valued on the basis of valuations furnished by a pricing service or at their
fair value as determined by the Board of Trustees, as described in the SAI. The
net asset value of each class of shares is effective for orders received in
"good order" by the dealer prior to its calculation and received by MFD prior to
the close of that business day. The Fund has authorized one or more dealers to
receive purchase and redemption orders on behalf of the Fund. Such dealers are
authorized to designate other intermediaries to receive purchase and redemption
orders on behalf of the Fund. The Fund will be deemed to have received a
purchase or redemption order when an authorized dealer or, if applicable, a
dealer's authorized designee, receives the order. Customer orders will
    
 
                                       29
<PAGE>   77
 
   
be priced at the net asset value of the Fund next computed after such orders are
received by an authorized dealer or the dealer's authorized designee.
    
 
DESCRIPTION OF SHARES, VOTING RIGHTS AND LIABILITIES
 
The Fund, one of four series of the Trust, has two classes of shares, entitled
Class A and Class B Shares of Beneficial Interest (without par value). The Trust
has reserved the right to create and issue additional classes and series of
shares, in which case each class of shares of a series would participate equally
in the earnings, dividends and assets of the particular class of shares of that
particular series. Shareholders are entitled to one vote for each share held and
shares of each series would be entitled to vote separately to approve investment
advisory agreements or changes in investment restrictions, but shares of all
series would be entitled to vote together in the election of Trustees and
selection of accountants. Additionally, each class of shares of a series will
vote separately on any material increases in the fees under the Distribution
Plan or on any other matter that affects solely that class of shares, but will
otherwise vote together with all other classes of shares of the series on all
other matters. The Trust does not intend to hold annual shareholders meetings.
The Declaration of Trust provides that a Trustee may be removed from office in
certain instances (see "Description of Shares, Voting Rights and Liabilities" in
the SAI).
 
Each share of a class of the Fund represents an equal proportionate interest in
the Fund with each other class share, subject to the liabilities of that
particular class. Shares have no pre-emptive or conversion rights (except as set
forth above in "Purchases -- Conversion of Class B Shares"). Shares are fully
paid and non-assessable. Should the Fund be liquidated, shareholders of each
class are entitled to share pro rata in the net assets attributable to that
class available for distribution to shareholders. Shares will remain on deposit
with the Shareholder Servicing Agent and certificates will not be issued except
in connection with pledges and assignments and in certain other limited
circumstances.
 
The Trust is an entity of the type commonly known as a "Massachusetts business
trust." Under Massachusetts law, shareholders of such a trust may, under certain
circumstances, be held personally liable as partners for its obligations.
However, the risk of a shareholder incurring financial loss on account of
shareholder liability is limited to circumstances in which both inadequate
insurance (e.g., fidelity bonding and errors and omissions insurance) existed
and the Trust itself was unable to meet its obligations.
 
PERFORMANCE INFORMATION
 
   
From time to time, the Fund will provide yield, current distribution rate,
tax-equivalent yield and total rate of return quotations for each class of
shares and may also quote fund rankings in the relevant fund category from
various sources, such as the Lipper Analytical Securities Corporation and
Wiesenberger Investment Companies Service. Yield and tax-equivalent yield
quotations are based on the annualized net investment income per share of a
class of the Fund over a 30-day period stated as a percent of the maximum public
offering price on the last day of that period. Yield calculations for Class B
shares assume no CDSC is paid. The current distribution rate for each class is
calculated by (i) annualizing the distributions (excluding short-term capital
gains) of the class for a stated period; (ii) adding any short-term capital
gains paid within the
    
 
                                       30
<PAGE>   78
 
   
immediately preceding twelve-month period; and (iii) dividing the result by the
maximum offering price or net asset value per share on the last day of the
period. Current distribution rate calculations for Class B shares assume no CDSC
is paid. The current distribution rate differs from the yield calculation
because it may include distributions to shareholders from sources other than
dividends and interest, such as premium income from option writing, short-term
capital gains, and return of invested capital, and may be calculated over a
different period of time. Total rate of return quotations reflect the average
annual percentage change over stated periods in the value of an investment in a
class of shares of the Fund made at the maximum public offering price of the
shares of that class with all distributions reinvested and which will give
effect to the imposition of any applicable CDSC assessed upon redemptions of the
Fund's Class B shares. Such total rate of return quotations may be accompanied
by quotations which do not reflect the reduction in value of the initial
investment due to the sales charge or the deduction of a CDSC, and which will
therefore be higher. The Fund offers multiple classes of shares which were
initially offered for sale to, and purchased by, the public on different dates
(the class "inception date"). The calculation of total rate of return for a
class of shares which has a later inception date than another class of shares of
the Fund is based both on (i) the performance of the Fund's newer class from its
inception date and (ii) the performance of the Fund's oldest class from its
inception date up to the class inception date of the newer class. See the SAI
for further information on the calculation of total rate of return for share
classes with different class inception dates.
    
 
   
All performance quotations are based on historical performance and are not
intended to indicate future performance. Yield and tax-equivalent yield reflect
only annualized net portfolio income as of a stated time and current
distribution rate reflects only the annualized rate of distributions paid by the
Fund over a stated period of time, while total rate of return reflects all
components of investment return. The Fund's quotations may from time to time be
used in advertisements, shareholder reports or other communications to
shareholders. For a discussion of the manner in which the Fund will calculate
its yield, current distribution rate, tax-equivalent yield and total rate of
return, see the SAI. For further information about the Fund's performance for
the fiscal year ended August 31, 1998, please see the Fund's Annual Report. A
copy of the annual report may be obtained without charge by contacting the
Shareholder Servicing Agent (see back cover for address and phone number). In
addition to information provided in shareholder reports, the Fund may, in its
discretion, from time to time, make a list of all or a portion of its holdings
available to investors upon request.
    
 
   
PROVISION OF ANNUAL AND SEMIANNUAL REPORTS
    
 
   
To avoid sending duplicate copies of materials to households, only one copy of
each Fund annual and semiannual report may be mailed to shareholders having the
same residential address on the Fund's records. However, any shareholder may
call the Shareholder Servicing Agent at 1-800-225-2606 to request that copies of
such reports be sent personally to that shareholder.
    
 
   
8.  SHAREHOLDER SERVICES
    
 
Shareholders with questions concerning the shareholder services described below
or concerning other aspects of the Fund should contact the Shareholder Servicing
Agent (see back cover for address and phone number).
                                       31
<PAGE>   79
 
ACCOUNT AND CONFIRMATION STATEMENTS -- Each shareholder will receive
confirmation statements showing the transaction activity in his account.
Cancelled checks, if any, will be sent to shareholders monthly. At the end of
each calendar year, each shareholder will receive information regarding the tax
status of reportable dividends and distributions for that year (see "Tax
Status").
 
DISTRIBUTION OPTIONS -- The following options are available to all accounts
(except Systematic Withdrawal Plan accounts) and may be changed as often as
desired by notifying the Shareholder Servicing Agent:
 
       -- Dividends and capital gain distributions reinvested in additional
          shares. This option will be assigned if no other option is specified;
 
       -- Dividends in cash; capital gain distributions reinvested in additional
          shares;
 
       -- Dividends and capital gain distributions in cash.
 
Reinvestments (net of any tax withholding) will be made in additional full and
fractional shares of the same class of shares at the net asset value in effect
at the close of business on the record date. Dividends and capital gains
distributions in amounts less than $10 will automatically be reinvested in
additional shares of the Fund. If a shareholder has elected to receive dividends
and/or capital gain distributions in cash, and the postal or other delivery
service is unable to deliver checks to shareholder's address of record, or the
shareholder does not respond to mailings from the Shareholder Servicing Agent
with regard to uncashed distribution checks, such shareholder's distribution
option will automatically be converted to having all dividends and other
distributions reinvested in additional shares. Any request to change a
distribution option must be received by the Shareholder Servicing Agent by the
record date for a dividend or distribution in order to be effective for that
dividend or distribution. No interest will accrue on amounts represented by
uncashed distribution or redemption checks.
 
INVESTMENT AND WITHDRAWAL PROGRAMS -- For the convenience of shareholders, the
Fund makes available the following programs designed to enable shareholders to
add to their investment in an account with the Fund or withdraw from it with a
minimum of paper work. The programs involve no extra charge to shareholders
(other than a sales charge in the case of certain Class A share purchases) and
may be changed or discontinued at any time by a shareholder or the Fund.
 
    LETTER OF INTENT:  If a shareholder (other than a group purchaser as
described in the SAI) anticipates purchasing $100,000 or more of Class A shares
of the Fund alone or in combination with shares of either class of other MFS
Funds or MFS Fixed Fund (a bank collective investment fund) within a 13-month
period (or 36-month period for purchases of $1 million or more), the shareholder
may obtain such shares at the same reduced sales charge as though the total
quantity were invested in one lump sum, subject to escrow agreements and the
appointment of an attorney for redemptions from the escrow amount if the
intended purchases are not completed, by completing the Letter of Intent section
of the Account Application.
 
    RIGHT OF ACCUMULATION:  A shareholder qualifies for cumulative quantity
discounts on purchases of Class A shares when his new investment, together with
the current offering price value of all holdings of Class A and Class B shares
of that shareholder in the MFS Funds or MFS Fixed Fund (a bank collective
investment fund), reaches a discount level.
                                       32
<PAGE>   80
 
    DISTRIBUTION INVESTMENT PROGRAM:  Shares of a particular class of the Fund
may be sold at net asset value (and without any applicable CDSC) through the
automatic reinvestment of dividends and capital gain distributions from the same
class of another MFS Fund. Furthermore, distributions made by the Fund may be
automatically invested at net asset value in shares of the same class of another
MFS Fund, if shares of such Fund are available for sale (without a sales charge
and not subject to any applicable CDSC).
 
    SYSTEMATIC WITHDRAWAL PLAN:  A shareholder may direct the Shareholder
Servicing Agent to send to him (or any one he designates) regular periodic
payments based upon the value of his account. Each payment under a Systematic
Withdrawal Plan (a "SWP") must be at least $100, except in certain limited
circumstances. The aggregate withdrawals of Class B shares in any year pursuant
to a SWP will not be subject to a CDSC and are generally limited to 10% of the
value of the account at the time of the establishment of the SWP. The CDSC will
not be waived in the case of SWP redemptions of Class A shares which are subject
to a CDSC.
 
DOLLAR COST AVERAGING PROGRAMS
 
    AUTOMATIC INVESTMENT PLAN:  Cash investments of $50 or more may be made
through a shareholder's checking account on any day of the month. If the
shareholder does not specify a date, the investment will automatically occur on
the first business day of the month. Required forms are available from the
Shareholder Servicing Agent or investment dealers.
 
    AUTOMATIC EXCHANGE PLAN:  Shareholders having account balances of at least
$5,000 in any MFS Fund may exchange their shares for the same class of shares of
the other MFS Funds under the Automatic Exchange Plan. The Automatic Exchange
Plan provides for automatic monthly or quarterly exchanges of funds from the
shareholder's account in an MFS Fund for investment in the same class of shares
of other MFS Funds selected by the shareholder. Under the Automatic Exchange
Plan, exchanges of at least $50 each may be made to up to six different funds. A
shareholder should consider the objectives and policies of a fund and review its
prospectus before electing to exchange money into such fund through the
Automatic Exchange Plan. No transaction fee is imposed in connection with
exchange transactions under the Automatic Exchange Plan. However, exchanges of
shares of MFS Money Market Fund, MFS Government Money Market Fund or Class A
shares of MFS Cash Reserve Fund will be subject to any applicable sales charge.
For federal and (generally) state income tax purposes, an exchange is treated as
a sale of the shares exchanged and, therefore, could result in a capital gain or
loss to the shareholder making the exchange. See the Statement of Additional
Information for further information concerning the Automatic Exchange Plan.
Investors should consult their tax advisers for information regarding the
potential capital gain and loss consequences of transactions under the Automatic
Exchange Plan.
 
Because a dollar cost averaging program involves periodic purchases of shares
regardless of fluctuating share offering prices, a shareholder should consider
his financial ability to continue his purchases through periods of low price
levels. Maintaining a dollar cost averaging program concurrently with a
withdrawal program could be disadvantageous because of the sales charges
included in share purchases in the case of Class A shares, and because of the
assessment of the CDSC for certain share redemptions in the case of Class A
shares.
                            ------------------------
 
                                       33
<PAGE>   81
 
   
The Fund's SAI, dated January 1, 1999, contains more detailed information about
the Fund, including, but not limited to, information related to (i) the Fund's
investment objective, policies and restrictions, (ii) the Trustees, officers and
investment adviser, (iii) portfolio trading, (iv) the method used to calculate
yield, tax-equivalent yield and total rate of return quotations of the Fund, (v)
the Distribution Plan and (vi) various services and privileges provided by the
Fund for the benefit of its shareholders, including additional information with
respect to the exchange privilege.
    
 
                                       34
<PAGE>   82
 
                                   APPENDIX A
 
WAIVERS OF SALES CHARGES
 
   
This Appendix sets forth the various circumstances in which all applicable sales
charges are waived (Section I), the initial sales charge and the contingent
deferred sales charge ("CDSC") for Class A shares are waived (Section II), and
the CDSC for Class B and Class C shares is waived (Section III). Some of the
following information will not apply to certain funds in the MFS Family of
Funds, depending on which classes of shares are offered by such fund. As used in
this Appendix, the term "dealer" includes any broker, dealer, bank (including
bank trust departments), registered investment adviser, financial planner and
any other financial institution having a selling agreement or other similar
agreement with MFS Fund Distributors, Inc. ("MFD").
    
 
I. WAIVERS OF ALL APPLICABLE SALES CHARGES
 
In the following circumstances, the initial charge imposed on purchases of Class
A shares and the CDSC imposed on certain redemptions of Class A shares and on
redemptions of Class B shares, as applicable, are waived:
 
1. DIVIDEND REINVESTMENT
 
  - Shares acquired through dividend or capital gain reinvestment; and
 
  - Shares acquired by automatic reinvestment of distributions of dividends and
    capital gains of any fund in the MFS Family of Funds ("MFS Funds") pursuant
    to the Distribution Investment Program.
 
2. CERTAIN ACQUISITIONS/LIQUIDATIONS
 
  - Shares acquired on account of the acquisition or liquidation of assets of
    other investment companies or personal holding companies.
 
3. AFFILIATES OF AN MFS FUND/CERTAIN DEALERS. SHARES ACQUIRED BY:
 
  - Officers, eligible directors, employees (including retired employees) and
    agents of Massachusetts Financial Services Company ("MFS"), Sun Life
    Assurance Company of Canada ("Sun Life") or any of their subsidiary
    companies;
 
  - Trustees and retired trustees of any investment company for which MFD serves
    as distributor;
 
  - Employees, directors, partners, officers and trustees of any sub-adviser to
    any MFS Fund;
 
  - Employees or registered representatives of dealers;
 
  - Certain family members of any such individual and their spouses identified
    above and certain trusts, pension, profit-sharing or other retirement plans
    for the sole benefit of such persons, provided the shares are not resold
    except to the MFS Fund which issued the Shares; and
 
                                       A-1
<PAGE>   83
 
  - Institutional Clients of MFS or MFS Institutional Advisors, Inc.
 
4. INVOLUNTARY REDEMPTIONS (CDSC WAIVER ONLY)
 
  - Shares redeemed at an MFS Fund's direction due to the small size of a
    shareholder's account. See "Redemptions and Repurchases -- General --
    Involuntary Redemptions/Small Accounts" in the Prospectus.
 
5. RETIREMENT PLANS (CDSC WAIVER ONLY).  Shares redeemed on account of
distributions made under the following circumstances:
 
  INDIVIDUAL RETIREMENT ACCOUNTS ("IRAS")
 
  - Death or disability of the IRA owner.
 
  SECTION 401(a) PLANS ("401(a) PLANS") AND SECTION 403(b) EMPLOYER SPONSORED
  PLANS ("ESP PLANS")
 
  - Death, disability or retirement of 401(a) or ESP Plan participant;
 
  - Loan from 401(a) or ESP Plan;
 
  - Financial hardship (as defined in Treasury Regulation Section
    1.401(k)-1(d)(2), as amended from time to time);
 
  - Termination of employment of 401(a) or ESP Plan participant (excluding,
    however, a partial or other termination of the Plan);
 
  - Tax-free return of excess 401(a) or ESP Plan contributions;
 
  - To the extent that redemption proceeds are used to pay expenses (or certain
    participant expenses) of the 401(a) or ESP Plan (e.g., participant account
    fees), provided that the Plan sponsor subscribes to the MFS FUNDamental
    401(k) Plan or another similar recordkeeping system made available by MFS
    Service Center, Inc. (the "Shareholder Servicing Agent"); and
 
  - Distributions from a 401(a) or ESP Plan that has invested its assets in one
    or more of the MFS Funds for more than 10 years from the later to occur of:
    (i) January 1, 1993 or (ii) the date such 401(a) or ESP Plan first invests
    its assets in one or more of the MFS Funds.
 
  - The sales charges will be waived in the case of a redemption of all of the
    401(a) or ESP Plan's shares in all MFS Funds (i.e., all the assets of the
    401(a) or ESP Plan invested in the MFS Funds are withdrawn), unless
    immediately prior to the redemption, the aggregate amount invested by the
    401(a) or ESP Plan in shares of the MFS Funds (excluding the reinvestment of
    distributions) during the prior four years equals 50% or more of the total
    value of the 401(a) or ESP Plan's assets in the MFS Funds, in which case the
    sales charges will not be waived.
 
   
  - Shares purchased by certain retirement plans or trust accounts if: (i) the
    plan is currently a party to a retirement plan recordkeeping or
    administrative services agreement with MFD or
    
 
                                       A-2
<PAGE>   84
 
   
one of its affiliates and (ii) the shares purchased or redeemed represent
transfers from or transfers to plan investments other than the MFS Funds of
which retirement plan recordkeeping services are provided under the terms of
     such agreement.
    
 
  SECTION 403(b) SALARY REDUCTION ONLY PLANS ("SRO PLANS")
 
  - Death or disability of SRO Plan participant.
 
6. CERTAIN TRANSFERS OF REGISTRATION (CDSC WAIVER ONLY). Shares transferred:
 
  - To an IRA rollover account where any sales charges with respect to the
    shares being reregistered would have been waived had they been redeemed; and
 
  - From a single account maintained for a 401(a) Plan to multiple accounts
    maintained by the Shareholder Servicing Agent on behalf of individual
    participants of such Plan, provided that the Plan sponsor subscribes to the
    MFS FUNDamental 401(k) Plan or another similar recordkeeping system made
    available by the Shareholder Servicing Agent.
 
7. LOAN REPAYMENTS
 
  - Shares acquired pursuant to repayments by retirement plan participants of
    loans from 401(a) or ESP Plans with respect to which such Plan or its
    sponsoring organization subscribes to the MFS FUNDamental 401(k) Program or
    the MFS Recordkeeper Plus Program (but not the MFS Recordkeeper Program).
 
II. WAIVERS OF CLASS A SALES CHARGES
 
In addition to the waivers set forth in Section I above, in the following
circumstances the initial sales charge imposed on purchases of Class A shares
and the CDSC imposed on certain redemptions of Class A shares are waived:
 
1. WRAP ACCOUNT AND FUND "SUPERMARKET" INVESTMENTS
 
  - Shares acquired by investments through certain dealers (including registered
    investment advisers and financial planners) which have established certain
    operational arrangements with MFD which include a requirement that such
    shares be sold for the sole benefit of clients participating in a "wrap"
    account, mutual fund "supermarket" account or a similar program under which
    such clients pay a fee to such dealer.
 
2. INVESTMENT BY INSURANCE COMPANY SEPARATE ACCOUNTS
 
  - Shares acquired by insurance company separate accounts.
 
3. RETIREMENT PLANS
 
  ADMINISTRATIVE SERVICES ARRANGEMENTS
 
  - Shares acquired by retirement plans or trust accounts whose third party
    administrators or dealers have entered into an administrative services
    agreement with MFD or one of its affiliates to perform certain
    administrative services, subject to certain operational and
 
                                       A-3
<PAGE>   85
 
minimum size requirements specified from time to time by MFD or one or more of
its affiliates.
 
  REINVESTMENT OF DISTRIBUTIONS FROM QUALIFIED RETIREMENT PLANS
 
  - Shares acquired through the automatic reinvestment in Class A shares of
    Class A or Class B distributions which constitute required withdrawals from
    qualified retirement plans.
 
  SHARES REDEEMED ON ACCOUNT OF DISTRIBUTIONS MADE UNDER THE FOLLOWING
CIRCUMSTANCES:
 
  IRAS
 
  - Distributions made on or after the IRA owner has attained the age of 59 1/2
    years old; and
 
  - Tax-free returns of excess IRA contributions.
 
  401(a) PLANS
 
  - Distributions made on or after the 401(a) Plan participant has attained the
    age of 59 1/2 years old; and
 
  - Certain involuntary redemptions and redemptions in connection with certain
    automatic withdrawals from a 401(a) Plan.
 
  ESP PLANS AND SRO PLANS
 
  - Distributions made on or after the ESP or SRO Plan participant has attained
    the age of 59 1/2 years old.
 
   
4. PURCHASES OF AT LEAST $5 MILLION (CDSC WAIVER ONLY)
    
 
   
  - Shares acquired of Eligible Funds (as defined below) if the shareholder's
    investment equals or exceeds $5 million in one or more Eligible Funds (the
    "Initial Purchase") (this waiver applies to the shares acquired from the
    Initial Purchase and all shares of Eligible Funds subsequently acquired by
    the shareholder); provided that the dealer through which the Initial
    Purchase is made enters into an agreement with MFD to accept delayed payment
    of commissions with respect to the Initial Purchase and all subsequent
    investments by the shareholder in the Eligible Funds subject to such
    requirements as may be established from time to time by MFD (for a schedule
    of the amount of commissions paid by MFD to the dealer on such investments,
    see "Purchases -- Class A Shares -- Purchases subject to a CDSC" in the
    Prospectus). The Eligible Funds are all funds included in the MFS Family of
    Funds, except for Massachusetts Investors Trust, Massachusetts Investors
    Growth Stock Fund, MFS Municipal Bond Fund, MFS Municipal Limited Maturity
    Fund, MFS Money Market Fund, MFS Government Money Market Fund and MFS Cash
    Reserve Fund.
    
 
   
5. BANK TRUST DEPARTMENTS AND LAW FIRMS
    
 
   
  - Shares acquired by certain bank trust departments or law firms acting as
    trustee or manager for trust accounts which have entered into an
    administrative services agreement with MFS and are acquiring such shares for
    the benefit of their trust account clients.
    
 
                                       A-4
<PAGE>   86
 
   
6. INVESTMENT OF PROCEEDS FROM CERTAIN REDEMPTIONS OF CLASS I SHARES
    
 
   
  - The initial sales charge imposed on purchases of Class A shares, and the
    contingent deferred sales charge imposed on certain redemptions of Class A
    shares, are waived with respect to Class A shares acquired of any of the MFS
    Funds through the immediate reinvestment of the proceeds of a redemption of
    Class I shares of any of the MFS Funds.
    
 
III. WAIVERS OF CLASS B SALES CHARGES
 
  - In addition to the waivers set forth in Section I above, in the following
    circumstances the CDSC imposed on redemptions of Class B shares is waived:
 
1. SYSTEMATIC WITHDRAWAL PLAN
 
  - Systematic Withdrawal Plan redemptions with respect to up to 10% per year
    (or 15% per year, in the case of accounts registered as IRAs where the
    redemption is made pursuant to Section 72(t) of the Internal Revenue Code of
    1986, as amended) of the account value at the time of establishment.
 
2. DEATH OF OWNER
 
  - Shares redeemed on account of the death of the account owner if the shares
    are held solely in the deceased individual's name or in a living trust for
    the benefit of the deceased individual.
 
3. DISABILITY OF OWNER
 
  - Shares redeemed on account of the disability of the account owner if shares
    are held either solely or jointly in the disabled individual's name or in a
    living trust for the benefit of the disabled individual (in which case a
    disability certification form is required to be submitted to the Shareholder
    Servicing Agent).
 
4. RETIREMENT PLANS.  Shares redeemed on account of distributions made under the
   following circumstances:
 
  IRAS, 401(a) PLANS, ESP PLANS AND SRO PLANS
 
  - Distributions made on or after the IRA owner or the 401(a), ESP or SRO Plan
    participant, as applicable, has attained the age of 70 1/2 years old, but
    only with respect to the minimum distribution under applicable Internal
    Revenue Code ("Code") rules.
 
  SALARY REDUCTION SIMPLIFIED EMPLOYEE PENSION PLANS ("SAR-SEP PLANS")
 
  - Distributions made on or after the SAR-SEP Plan participant has attained the
    age of 70 1/2 years old, but only with respect to the minimum distribution
    under applicable Code rules; and
 
  - Death or disability of a SAR-SEP Plan participant.
 
                                       A-5
<PAGE>   87
 
                                   APPENDIX B
 
                         TAXABLE EQUIVALENT YIELD TABLE
   
               (UNDER FEDERAL INCOME TAX LAW AND RATES FOR 1998)
    
 
   
    The table below shows the approximate taxable bond yields which are
equivalent to tax-exempt bond yields from 3% to 8% under federal income tax laws
that apply to 1998. (Such yields may differ under the laws applicable to
subsequent years.) Separate calculations, showing the applicable taxable income
brackets, are provided for investors who file joint returns and for those
investors who file individual returns.
    
 
   
<TABLE>
<CAPTION>
  SINGLE RETURN       JOINT RETURN       INCOME                 TAX-EXEMPT YIELD
- -----------------   -----------------      TAX      -----------------------------------------   FEDERAL
          (TAXABLE INCOME)*             BRACKET**    3%     4%     5%     6%     7%      8%      RATE
- -------------------------------------   ---------   ----   ----   ----   ----   -----   -----   -------
      1998                1998                              EQUIVALENT TAXABLE YIELD
<S>                 <C>                 <C>         <C>    <C>    <C>    <C>    <C>     <C>     <C>
$      0-$ 25,350   $      0-$ 42,350      0.15%    3.53%  4.71%  5.88%  7.06%   8.24%   9.41%     0.15%
$ 25,350-$ 61,400   $ 42,350-$102,300     28.00     4.17   5.56   6.94   8.33    9.72   11.11      0.28
$ 61,400-$128,100   $102,300-$155,950     31.00     4.35   5.80   7.25   8.70   10.14   11.59      0.31
$128,100-$278,450   $155,950-$278,450      0.36     4.69   6.25   7.81   9.38   10.94   12.50      0.36
  $278,450 & Over     $278,450 & Over      0.396    4.97   6.62   8.28   9.93   11.59   13.25     0.396
</TABLE>
    
 
 *Net amount subject to Federal personal income tax after deductions and
  exemptions.
 
**The effective marginal income tax rate will be increased if personal
  exemptions are phased out (for the phase out period only) and if a portion of
  itemized deductions are disallowed. This increase in the marginal rates, if
  applicable, will cause a corresponding increase in the equivalent taxable
  yields.
 
While it is expected that a substantial portion of the interest income
distributed to the Fund's shareholders will be exempt from federal income taxes,
portions of such distributions from time to time may be subject to federal
income taxes or a federal alternative minimum tax.
 
                                       B-1
<PAGE>   88
 
                                   APPENDIX C
 
DESCRIPTION OF MUNICIPAL BONDS
 
Municipal Bonds include debt obligations issued to obtain funds for various
public purposes, including the construction of a wide range of public facilities
such as bridges, highways, housing, hospitals, mass transportation, schools,
streets and water and sewer works. Other public purposes for which Municipal
Bonds may be issued include refunding outstanding obligations, obtaining funds
for general operating expenses and obtaining funds to loan to other public
institutions and facilities. In addition, certain types of industrial
development bonds are issued by or on behalf of public authorities to obtain
funds to provide privately-operated housing facilities, sports facilities,
convention or trade show facilities, airport, mass transit, port or parking
facilities, air or water pollution control facilities for water supply, gas,
electricity or sewage or solid waste disposal. Such obligations are included in
the term Municipal Bonds if the interest paid thereon qualifies as exempt from
federal income tax. Other types of industrial development bonds, the proceeds of
which are used for the construction, equipment, repair or improvement of
privately operated industrial or commercial facilities, may constitute Municipal
Bonds, although the current federal tax laws place substantial limitations on
the size of such issues.
 
The two principal classifications of Municipal Bonds are "general obligation"
and "revenue" bonds. General obligation bonds are secured by the issuer's pledge
of its good faith, credit and taxing power for the payment of principal and
interest. The payment of such bonds may be dependent upon an appropriation by
the issuer's legislative body. The characteristics and enforcement of general
obligation bonds vary according to the law applicable to the particular issuer.
Revenue bonds are payable only from the revenues derived from a particular
facility or class of facilities, or, in some cases, from the proceeds of a
special excise or other specific revenue source. Industrial development bonds
which are Municipal Bonds are in most cases revenue bonds and do not generally
constitute the pledge of the credit of the issuer of such bonds.
 
Municipal Bonds also include participations in municipal leases. These are
undivided interests in a portion of an obligation in the form of a lease or
installment purchase which is issued by state and local governments to acquire
equipment and facilities. Municipal leases frequently have special risks not
normally associated with general obligation or revenue bonds. Leases and
installment purchase or conditional sale contracts (which normally provide for
title to the leased asset to pass eventually to the governmental issuer) have
evolved as a means for governmental issuers to acquire property and equipment
without meeting the constitutional and statutory requirements for the issuance
of debt. The debt-issuance limitations are deemed to be inapplicable because of
the inclusion in many leases or contracts of "non-appropriation" clauses that
provide that the governmental issuer has no obligation to make future payments
under the lease or contract unless money is appropriated for such purpose by the
appropriate legislative body on a yearly or other periodic basis. Although the
obligations will be secured by the leased equipment or facilities, the
disposition of the property in the event of non-appropriation or foreclosure
might, in some cases, prove difficult. In light of these concerns, the Fund has
adopted and follows procedures for determining whether municipal lease
securities purchased by the Fund are liquid and for monitoring the liquidity of
municipal lease securities held in the Fund's portfolio. The procedures require
that a number of factors be used in evaluating the liquidity of a municipal
lease security, including, the frequency of trades and quotes for the security,
the
 
                                       C-1
<PAGE>   89
 
number of dealers willing to purchase or sell the security and the number of
other potential purchasers, the willingness of dealers to undertake to make a
market in the security, the nature of the marketplace in which the security
trades, the credit quality of the security and other factors which the Adviser
may deem relevant. There are, of course, variations in the security of Municipal
Bonds, both within a particular classification and between classifications,
depending on numerous factors.
 
The yields on Municipal Bonds are dependent on a variety of factors, including
general money market conditions, supply and demand and general conditions of the
Municipal Bond market, size of a particular offering, the maturity of the
obligation and rating of the issue.
 
DESCRIPTION OF OTHER INVESTMENTS
 
    U.S. GOVERNMENT OBLIGATIONS -- are issued by the Treasury and include bills,
certificates of indebtedness, notes and bonds. Agencies and instrumentalities of
the U.S. Government are established under the authority of an act of Congress
and include, but are not limited to, the Government National Mortgage
Association, the Tennessee Valley Authority, the Bank for Cooperatives, the
Farmers Home Administration, Federal Home Loan Banks, Federal Intermediate
Credit Banks, Federal Land Banks and the Federal National Mortgage Association.
 
    CERTIFICATES OF DEPOSIT -- are certificates issued against funds deposited
in a commercial bank, are for a definite period of time, earn a specified rate
of return and are normally negotiable.
 
    BANKERS' ACCEPTANCES -- are short-term credit instruments used to finance
the import, export, transfer or storage of goods. They are termed "accepted"
when a bank guarantees their payment at maturity.
 
    COMMERCIAL PAPER -- refers to promissory notes issued by corporations in
order to finance their short-term credit needs.
 
   
The ratings of Moody's Investors Service, Inc. ("Moody's"), Standard & Poor's
Ratings Group ("S&P") and Fitch IBCA ("Fitch") represent their opinions as to
the quality of various Municipal Bonds. It should be emphasized, however, that
ratings are not absolute standards of quality. Consequently, Municipal Bonds
with the same maturity, coupon and rating may have different yields while Bonds
of the same maturity and coupon with different ratings may have the same yield.
    
 
DESCRIPTION OF MUNICIPAL BOND RATINGS
 
  Moody's
 
Aaa: Bonds which are rated Aaa are judged to be of the best quality. They carry
the smallest degree of investment risk and are generally referred to as "gilt
edged." Interest payments are protected by a large or by an exceptionally stable
margin and principal is secure. While the various protective elements are likely
to change, such changes as can be visualized are most unlikely to impair the
fundamentally strong position of such issues.
 
Aa: Bonds which are rated Aa are judged to be of high quality by all standards.
Together with the Aaa group they comprise what are generally known as high grade
bonds. They are rated lower than the best bonds because margins of protection
may not be as large as in Aaa securities or
 
                                       C-2
<PAGE>   90
 
fluctuation of protective elements may be of greater amplitude or there may be
other elements present which make the long term risks appear somewhat larger
than in Aaa securities.
 
A: Bonds which are rated A possess many favorable investment attributes and are
to be considered as upper-medium-grade obligations. Factors giving security to
principal and interest are considered adequate, but elements may be present
which suggest a susceptibility to impairment sometime in the future.
 
Baa: Bonds which are rated Baa are considered as medium-grade obligations,
(i.e., they are neither highly protected nor poorly secured). Interest payments
and principal security appear adequate for the present but certain protective
elements may be lacking or may be characteristically unreliable over any great
length of time. Such bonds lack outstanding investment characteristics and in
fact have speculative characteristics as well.
 
   
                       STANDARD & POOR'S RATING SERVICES
    
 
   
AAA: An obligation rated AAA has the highest rating assigned by S&P. The
obligor's capacity to meet its financial commitment on the obligation is
EXTREMELY STRONG.
    
 
   
AA: An obligation rated AA differs from the highest rated obligations only in
small degree. The obligor's capacity to meet its financial commitment on the
obligation is VERY STRONG.
    
 
   
A: An obligation rated A is somewhat more susceptible to the adverse effects of
changes in circumstances and economic conditions than obligations in higher
rated categories. However, the obligor's capacity to meet its financial
commitment on the obligation is still STRONG.
    
 
   
BBB: An obligation rated BBB exhibits ADEQUATE protection parameters. However,
adverse economic conditions or changing circumstances are more likely to lead to
a weakened capacity of the obligor to meet its financial commitment on the
obligation.
    
 
   
Obligations rated BB, B, CCC, CC, and C are regarded as having significant
speculative characteristics. BB indicates the least degree of speculation and C
the highest. While such obligations will likely have some quality and protective
characteristics, these may be outweighed by large uncertainties or major
exposures to adverse conditions.
    
 
   
BB: An obligation rated BB is LESS VULNERABLE to nonpayment than other
speculative issues. However, it faces major ongoing uncertainties or exposure to
adverse business, financial, or economic conditions which could lead to the
obligor's inadequate capacity to meet its financial commitment on the
obligation.
    
 
   
B: An obligation rated B is MORE VULNERABLE to nonpayment than obligations rated
BB, but the obligor currently has the capacity to meet its financial commitment
on the obligation. Adverse business, financial, or economic conditions will
likely impair the obligor's capacity or willingness to meet its financial
commitment on the obligation.
    
 
   
CCC: An obligation rated CCC is CURRENTLY VULNERABLE to nonpayment and is
dependent upon favorable business, financial, and economic conditions for the
obligor to meet its financial commitment on the obligation. In the event of
adverse business, financial, or economic conditions the obligor is not likely to
have the capacity to meet its financial commitment on the obligation.
    
 
                                       C-3
<PAGE>   91
 
   
CC: An obligation rated CC is CURRENTLY HIGHLY VULNERABLE to nonpayment.
    
 
   
C: The C rating may be used to cover a situation where a bankruptcy petition has
been filed or similar action has been taken, but payments on this obligation are
being continued.
    
 
   
D: An obligation rated D is in payment default. The D rating category is used
when payments on an obligation are not made on the date due even if the
applicable grace period has not expired, unless Standard & Poor's believes that
such payments will be made during such grace period. The D rating also will be
used upon the filing of a bankruptcy petition or the taking of a similar action
if payments on an obligation are jeopardized.
    
 
   
PLUS (+) OR MINUS (-) The ratings from AA to CCC may be modified by the addition
of a plus or minus sign to show relative standing with the major rating
categories.
    
 
   
r: This symbol is attached to the ratings of instruments with significant
noncredit risks. If highlights risks to principal or volatility of expected
returns which are not addressed in the credit rating. Examples include:
obligations linked or indexed to equities, currencies, or commodities;
obligations exposed to severe prepayment risk -- such as interest-only or
principal-only mortgage securities; and obligations with unusually risky
interest terms, such as inverse floaters.
    
 
   
                                   FITCH IBCA
    
 
   
AAA: Highest credit quality. AAA ratings denote the lowest expectation of credit
risk. They are assigned only in case of exceptionally strong capacity for timely
payment of financial commitments. This capacity is highly unlikely to be
adversely affected by foreseeable events.
    
 
   
AA: Very high credit quality. AA ratings denote a very low expectation of credit
risk. They indicate very strong capacity for timely payment of financial
commitments. This capacity is not significantly vulnerable to foreseeable
events.
    
 
   
A: High credit quality. A ratings denote a low expectation of credit risk. The
capacity for timely payment of financial commitments is considered strong. This
capacity may, nevertheless, be more vulnerable to changes in circumstances or in
economic conditions than is the case for higher ratings.
    
 
   
BBB: Good credit quality. BBB ratings indicate that there is currently a low
expectation of credit risk. The capacity for timely payment of financial
commitments is considered adequate, but adverse changes in circumstances and in
economic conditions are more likely to impair this capacity. This is the lowest
investment-grade category.
    
 
   
Speculative Grade
    
 
   
BB: Speculative. BB ratings indicate that there is a possibility of credit risk
developing, particularly as the result of adverse economic change over time;
however, business or financial alternatives may be available to allow financial
commitments to be met. Securities rated in this category are not investment
grade.
    
 
   
B: Highly speculative. B ratings indicate that significant credit risk is
present, but a limited margin of safety remains. Financial commitments are
currently being met; however, capacity for
    
 
                                       C-4
<PAGE>   92
 
   
continued payment is contingent upon a sustained, favorable business and
economic environment.
    
 
   
CCC, CC, C: High default risk. Default is a real possibility. Capacity for
meeting financial commitments is solely reliant upon sustained, favorable
business or economic developments. A CC rating indicates that default of some
kind appears probable. C ratings signal imminent default.
    
 
   
DDD, DD, D: Default. Securities are not meeting current obligations and are
extremely speculative. DDD designates the highest potential for recovery of
amounts outstanding on any securities involved. For U.S. corporates, for
example, DD indicates expected recovery of 50% -- 90% of such outstandings, and
D the lowest recovery potential, i.e. below 50%.
    
 
   
                        DUFF & PHELPS CREDIT RATING CO.
    
 
   
AAA: Highest credit quality. The risk factors are negligible, being only
slightly more than for risk-free U.S. Treasury debt.
    
 
   
AA+, AA, AA-: High credit quality. Protection factors are strong. Risk is modest
but may vary slightly from time to time because of economic conditions.
    
 
   
A+, A, A-: Protection factors are average but adequate. However, risk factors
are more variable and greater in periods of economic stress.
    
 
   
BBB+, BBB, BBB-: Below average protection factors but still considered
sufficient for prudent investment. Considerable variability in risk during
economic cycles.
    
 
   
BB+, BB, BB-: Below investment grade but deemed likely to meet obligations when
due. Present or prospective financial protection factors fluctuate according to
industry conditions or company fortunes. Overall quality may move up or down
frequently within this category.
    
 
   
B+, B, B-: Below investment grade and possessing risk that obligations will not
be met when due. Financial protection factors will fluctuate widely according to
economic cycles, industry conditions and/or company fortunes. Potential exists
for frequent changes in the rating within this category or into a higher or
lower rating grade.
    
 
   
CCC: Well below investment-grade securities. Considerable uncertainty exists as
to timely payment of principal, interest or preferred dividends. Protection
factors are narrow and risk can be substantial with unfavorable
economic/industry conditions, and/or with unfavorable company developments.
    
 
   
DD: Defaulted debt-obligations. Issuer failed to meet scheduled principal and/or
interest payments.
    
 
   
DP: Preferred stock with dividend arrearages.
    
 
   
                        DUFF & PHELPS SHORT-TERM RATINGS
    
 
   
D-1+: Highest certainty of timely payment. Short-term liquidity, including
internal operation factors and/or access to alternative sources of funds, is
outstanding and safety is just below risk-free U.S. Treasury short-term
obligations.
    
 
                                       C-5
<PAGE>   93
 
Investment Adviser
Massachusetts Financial
Services Company
500 Boylston Street
Boston, MA 02116
(617) 954-5000
 
Distributor
MFS Fund Distributors, Inc.
500 Boylston Street
Boston, MA 02116
(617) 954-5000
 
Custodian and Dividend
Disbursing Agent
State Street Bank and Trust Company
225 Franklin Street
Boston, MA 02110
 
Shareholder Servicing Agent
MFS Service Center, Inc.
500 Boylston Street
Boston, MA 02116
Toll-free: (800) 225-2606
 
Mailing Address:
P.O. Box 2281
Boston, MA 02107-9906
 
Independent Auditors
Deloitte & Touche LLP
125 Summer Street
Boston, MA 02110
<PAGE>   94
 
[MFS Logo]
 
   
<TABLE>
<S>                                               <C>
MFS(R) MUNICIPAL                                  STATEMENT OF
BOND FUND                                         ADDITIONAL INFORMATION
(A member of the MFS Family of Funds(R))
                                                  January 1, 1999
</TABLE>
    
 
- --------------------------------------------------------------------------------
 
   
<TABLE>
<CAPTION>
                                                              PAGE
                                                              ----
<S>                                                          <C>
 1. Definitions.............................................       2
 2. Investment Objective, Policies and Restrictions.........       2
 3. Management of the Fund..................................       8
       Trustees.............................................       8
       Officers.............................................       8
       Trustee Compensation Table...........................       9
       Investment Adviser...................................       9
       Administrator........................................      10
       Custodian............................................      10
       Shareholder Servicing Agent..........................      10
       Distributor..........................................      11
 4. Portfolio Transactions and Brokerage Commissions........      12
 5. Shareholder Services....................................      12
       Investment and Withdrawal Programs...................      12
       Exchange Privilege...................................      14
 6. Tax Status..............................................      15
 7. Determination of Net Asset Value and Performance........      17
 8. Distribution Plan.......................................      19
 9. Description of Shares, Voting Rights and Liabilities....      20
10. Independent Auditors and Financial Statements...........      21
    Appendix A..............................................     A-1
</TABLE>
    
 
MFS MUNICIPAL BOND FUND
A Series of MFS Series Trust IV
500 Boylston Street, Boston, Massachusetts 02116
(617) 954-5000
 
   
This Statement of Additional Information, as amended or supplemented from time
to time (the "SAI"), sets forth information which may be of interest to
investors but which is not necessarily included in the Fund's Prospectus, dated
January 1, 1999. This SAI should be read in conjunction with the Prospectus, a
copy of which may be obtained without charge by contacting the Shareholder
Servicing Agent (see last page for address and phone number).
    
 
THIS SAI IS NOT A PROSPECTUS AND IS AUTHORIZED FOR DISTRIBUTION TO PROSPECTIVE
INVESTORS ONLY IF PRECEDED OR ACCOMPANIED BY A CURRENT PROSPECTUS.
<PAGE>   95


1.   DEFINITIONS
   
<TABLE>
<S>                              <C>  <C>


  "Fund"                         --   MFS Municipal Bond Fund,
                                      a
                                      diversified series of
                                      MFS(R) Series Trust IV
                                      (the "Trust"), a
                                      Massachusetts business
                                      trust. The Trust was
                                      known as Massachusetts
                                      Cash Management Trust
                                      prior to August 27,
                                      1993.
  "MFS" or the "Adviser"         --   Massachusetts Financial
                                      Services Company, a
                                      Delaware corporation.
  "MFD"                          --   MFS Fund Distributors,
                                      Inc., a Delaware
                                      corporation.
  "Prospectus"                   --   The Prospectus of the
                                      Fund, dated January 1,
                                      1999, as amended or
                                      supplemented from time
                                      to time.
</TABLE>
    
 
2.   INVESTMENT OBJECTIVE, POLICIES AND RESTRICTIONS
INVESTMENT OBJECTIVE. The Fund's investment objective is to provide as high a
level of current income exempt from federal income taxes as is considered
consistent with prudent investing and protection of shareholders' capital. Any
investment involves risk and there can be no assurance that the Fund will
achieve its investment objective.
 
INVESTMENT POLICIES. The investment policies of the Fund are described in the
Prospectus. In addition, certain of the Fund's investment policies are described
in greater detail below.
 
  "WHEN-ISSUED" SECURITIES: The Fund may purchase securities on a "when-issued"
or on a "forward delivery" basis. When the Fund commits to purchase a security
on a "when-issued" or on a "forward delivery" basis, it will set up procedures
consistent with the General Statement of Policy of the Securities and Exchange
Commission (the "SEC") concerning such purchases. Since that policy currently
recommends that an amount of the Fund's assets equal to the amount of the
purchase be held aside or segregated to be used to pay for the commitment, the
Fund will always have liquid assets sufficient to cover any commitments or to
limit any potential risk. However, although the Fund does not intend to make
such purchases for speculative purposes and intends to adhere to the provisions
of the SEC policy, purchases of securities on such bases may involve more risk
than other types of purchases. For example, the Fund may have to sell assets
which have been set aside in order to meet redemptions. Also, if the Fund
determines it is necessary to sell the "when-issued" or "forward delivery"
securities before delivery, the Fund may incur a loss because of market
fluctuations since the time the commitment to purchase such securities was made
and any gain or loss would not be tax-exempt.
 
  REPURCHASE AGREEMENTS: As described in the Prospectus, the Fund may enter into
repurchase agreements with sellers who are member firms (or a subsidiary
thereof) of the New York Stock Exchange (the "Exchange") or members of the
Federal Reserve System, recognized primary U.S. Government securities dealers or
institutions which the Adviser has determined to be of comparable
creditworthiness. The securities that the Fund purchases and holds through its
agent are U.S. Government securities, the values of which are equal to or
greater than the repurchase price agreed to be paid by the seller. The
repurchase price may be higher than the purchase price, the difference being
income to the Fund, or the purchase and repurchase prices may be the same, with
interest at a standard rate due to the Fund together with the repurchase price
on repurchase. In either case, the income to the Fund is unrelated to the
interest rate on the U.S. Government securities.
 
   
The repurchase agreement provides that in the event the seller fails to pay the
amount agreed upon on the agreed upon delivery date or upon demand, as the case
may be, the Fund will have the right to liquidate the securities. If at the time
the Fund is contractually entitled to exercise its right to liquidate the
securities, the seller is subject to a proceeding under the bankruptcy laws or
its assets are otherwise subject to a stay order, the Fund's exercise of its
right to liquidate the securities may be delayed and result in certain losses
and costs to the Fund. The Fund has adopted and follows procedures which are
intended to minimize the risks of repurchase agreements. For example, the Fund
only enters into repurchase agreements after the Adviser has determined that the
seller is creditworthy, and the Adviser monitors that seller's creditworthiness
on an ongoing basis. Moreover, under such agreements, the value of the
securities (which are marked to market every business day) is required to be
greater than the repurchase price, and the Fund has the right to make margin
calls at any time if the value of the securities falls below the agreed upon
collateral. The Fund may not invest more than 15% of its assets in repurchase
agreements maturing in more than seven days.
    
 
  INVERSE FLOATING RATE OBLIGATIONS: The Fund may invest in so-called "inverse
floating rate obligations" or "residual interest" bonds or certificates
structured to have similar features. In creating such an obligation, a
municipality issues a certain amount of debt and pays a fixed interest rate. A
portion of the debt is issued as variable rate short-term obligations, the
interest rate of which is reset at short intervals, typically ranging from
thirty-five days to one year. The other portion of the debt is issued as inverse
floating rate obligations, the interest rate of which is calculated based on the
difference between the entire amount of interest paid by the issuer on all of
the debt and the interest paid on the short-term obligation. Under usual
circumstances, the holder of the inverse floating rate obligation can generally
purchase an equal principal amount of the short-term obligation and link the two
obligations in order to create long-term fixed-rate bonds. Because the interest
rate on the inverse floating rate obligation is determined by subtracting the
short-term rate from a fixed amount, the interest rate will decrease as the
short-term rate increases and will increase as the short-term rate decreases.
The magnitude of increases and decreases in the market value of inverse floating
rate obligations may be approximately twice as large (or more if the inverse
instrument is issued in principal amount greater than the principal amount of
the short-term piece) as the comparable change in the market
 
                                        2
<PAGE>   96
 
value of an equal principal amount of long-term bonds which bear interest at the
rate paid by the issuer and have similar credit quality, redemption and maturity
provisions.
 
   
  OPTIONS: The Fund intends to write covered put and call options and purchase
put and call options on fixed income securities that are traded on U.S.
securities exchanges and over-the-counter. Call options written by the Fund give
the holder the right to buy the underlying securities from the Fund at a fixed
exercise price; put options written by the Fund give the holder the right to
sell the underlying securities to the Fund at a fixed exercise price. A call
option written by the Fund is "covered" if the Fund owns the underlying security
covered by the call or has an absolute and immediate right to acquire that
security without additional cash consideration (or for additional cash
consideration segregated by the Fund) upon conversion or exchange of other
securities held in its portfolio. A call option is also covered if the Fund
holds a call on the same security and in the same principal amount as the call
written where the exercise price of the call held (a) is equal to or less than
the exercise price of the call written or (b) is greater than the exercise price
of the call written if liquid assets representing the difference are segregated
by the Fund. A put option written by the Fund is "covered" if the Fund
segregates liquid assets with a value equal to the exercise price, or else holds
a put on the same security and in the same principal amount as the put written
where the exercise price of the put held is (a) equal to or greater than the
exercise price of the put written or (b) is less than the exercise price of the
put written if liquid assets representing the difference are segregated by the
Fund. Put and call options written by the Fund may also be covered in such other
manner as may be in accordance with the requirements of the exchange on which,
or the counter party with which, the option is traded, and applicable laws and
regulations. The writer of an option may have no control over when the
underlying securities must be sold, in the case of a call option, or purchased,
in the case of a put option, since with regard to certain options, the writer
may be assigned an exercise notice at any time prior to the termination of the
obligation.
    
 
Effecting a closing transaction in the case of a written call option will permit
the Fund to write another call option on the underlying security with either a
different exercise price or expiration date or both, or in the case of a written
put option will permit the Fund to write another put option to the extent that
the exercise price thereof is secured by liquid assets. Such transactions permit
the Fund to generate additional premium income, which will partially offset
declines in the value of portfolio securities or increases in the cost of
securities to be acquired. Also, effecting a closing transaction will permit the
cash or proceeds from the concurrent sale of any securities subject to the
option to be used for other Fund investments. If the Fund desires to sell a
particular security from its portfolio on which it has written a call option, it
will effect a closing transaction prior to or concurrent with the sale of the
security.
 
The Fund will realize a profit from a closing transaction if the price of the
transaction is less than the premium received from writing the option or is more
than the premium paid to purchase the option; the Fund will realize a loss from
a closing transaction if the price of the transaction is more than the premium
received from writing the option or is less than the premium paid to purchase
the option. Because increases in the market price of a call option will
generally reflect increases in the market price of the underlying security, any
loss resulting from the closing out of a call option is likely to be offset in
whole or in part by appreciation of the underlying security owned by the Fund.
 
An option position may be closed out only where there exists a secondary market
for an option of the same series. If a secondary market does not exist, it might
not be possible to effect closing transactions in particular options with the
result that the Fund would have to exercise the options in order to realize any
profit. If the Fund is unable to effect a closing purchase transaction in a
secondary market, it will not be able to sell the underlying security until the
option expires or it delivers the underlying security upon exercise. Reasons for
the absence of a liquid secondary market include the following: (i) there may be
insufficient trading interest in certain options; (ii) restrictions may be
imposed by a national securities exchange on opening transactions or closing
transactions or both; (iii) trading halts, suspensions or other restrictions may
be imposed with respect to particular classes or series of options or underlying
securities; (iv) unusual or unforeseen circumstances may interrupt normal
operations on an exchange; (v) the facilities of an exchange or the Options
Clearing Corporation (the "OCC") may not at all times be adequate to handle
current trading volume; or (vi) one or more exchanges could, for economic or
other reasons, decide or be compelled at some future date to discontinue the
trading of options (or a particular class or series of options), in which event
the secondary market on that exchange (or in that class or series of options)
would cease to exist, although outstanding options on that exchange that had
been issued by the OCC as a result of trades on that exchange would continue to
be exercisable in accordance with their terms.
 
The Fund may write options in connection with buy-and-write transactions; that
is, the Fund may purchase a security and then write a call option against that
security. The exercise price of the call the Fund determines to write will
depend upon the expected price movement of the underlying security. The exercise
price of a call option may be below ("in-the-money"), equal to ("at-the-money")
or above ("out-of-the-money") the current value of the underlying security at
the time the option is written. If the call options are exercised in such
transactions, the Fund's maximum gain will be the premium received by it for
writing the option, adjusted upwards or downwards by the difference between the
Fund's purchase price of the security and the exercise price. If the options are
not exercised and the price of the underlying security declines, the amount of
such decline will be offset in part, or entirely, by the premium received.
 
The writing of covered put options is similar in terms of risk/return
characteristics to buy-and-write transactions. Put options may be used by the
Fund in the same market environments that call options are used in equivalent
buy-and-write transactions.
 
                                        3
<PAGE>   97
 
The Fund may write combinations of put and call options on the same security, a
practice known as a "straddle." By writing a straddle, the Fund undertakes a
simultaneous obligation to sell and purchase the same security in the event that
one of the options is exercised. If the price of the security subsequently rises
sufficiently above the exercise price to cover the amount of the premium and
transaction costs, the call will likely be exercised and the Fund will be
required to sell the underlying security at a below market price. This loss may
be offset, however, in whole or in part, by the premiums received on the writing
of the two options. Conversely, if the price of the security declines by a
sufficient amount, the put will likely be exercised. The writing of straddles
will likely be effective, therefore, only where the price of a security remains
stable and neither the call nor the put is exercised. In an instance where one
of the options is exercised, the loss on the purchase or sale of the underlying
security may exceed the amount of the premiums received.
 
The Fund may purchase put options to hedge against a decline in the value of its
portfolio. By using put options in this way, the Fund will reduce any profit it
might otherwise have realized in the underlying security by the amount of the
premium paid for the put option and by transaction costs.
 
The Fund may purchase call options to hedge against an increase in the price of
securities that the Fund anticipates purchasing in the future. The premium paid
for the call option plus any transaction costs will reduce the benefit, if any,
realized by the Fund upon exercise of the option, and, unless the price of the
underlying security rises sufficiently, the option may expire worthless to the
Fund.
 
The Fund may also purchase warrants on fixed income securities. A warrant on a
fixed income security is a long-dated call option that provides the holder with
the right, but not the obligation, to purchase from an issuer a fixed income
security with a specified par value, coupon, and maturity at a fixed exercise
price on a specified date or between specified dates. Typically, the fixed
income securities that are deliverable pursuant to the warrant will be
noncallable securities. Warrants may be issued as entirely separate securities
or they may be attached to, but subsequently detachable from, a fixed income
security of the same issuer.
 
The staff of the SEC has taken the position that purchased over-the-counter
options and assets used to cover written over-the-counter options are illiquid
and, therefore, together with other illiquid securities, cannot exceed a certain
percentage of the Fund's assets (the "SEC illiquidity ceiling"). Although the
Adviser disagrees with this position, the Adviser intends to limit the Fund's
writing of over-the-counter options in accordance with the following procedure.
Except as provided below, the Fund intends to write over-the-counter options
only with primary U.S. Government securities dealers recognized by the Federal
Reserve Bank of New York. Also, the contracts which the Fund has in place with
such primary dealers will provide that the Fund has the absolute right to
repurchase an option it writes at any time at a price which represents the fair
market value, as determined in good faith through negotiation between the
parties, but which in no event will exceed a price determined pursuant to a
formula in the contract. Although the specific formula may vary between
contracts with different primary dealers, the formula will generally be based on
a multiple of the premium received by the Fund for writing the option, plus the
amount, if any, of the option's intrinsic value (i.e., the amount that the
option is in-the-money). The formula may also include a factor to account for
the difference between the price of the security and the strike price of the
option if the option is written out-of-the-money. The Fund will treat all or a
portion of the formula price as illiquid for purposes of the SEC illiquidity
ceiling imposed by the SEC staff. The Fund may also write over-the-counter
options with non-primary dealers and will treat the assets used to cover these
options as illiquid for purposes of such SEC illiquidity ceiling.
 
  FUTURES CONTRACTS: The Fund may enter into contracts for the future delivery
of fixed income securities or contracts based on Municipal Bond or other
financial indices, including any index of fixed income securities, as such
contracts become available for trading ("Futures Contracts"). The Fund may enter
into Futures Contracts for hedging purposes as well as non-hedging purposes. A
"sale" of a Futures Contract means a contractual obligation to deliver the
securities called for by the contract at a specified price in a fixed delivery
month or, in the case of a Futures Contract on an index of securities, to make
or receive a cash settlement. A "purchase" of a Futures Contract means a
contractual obligation to acquire the securities called for by the contract at a
specified price in a fixed delivery month or, in the case of a Futures Contract
on an index of securities, to make or receive a cash settlement. Futures
Contracts have been designed by exchanges which have been designated as
"contract markets" by the Commodity Futures Trading Commission (the "CFTC"), and
must be executed through a futures commission merchant, or brokerage firm, which
is a member of the relevant contract market. Existing contract markets include
the Chicago Board of Trade and the International Monetary Market of the Chicago
Mercantile Exchange. Futures Contracts are traded on these markets, and, through
their clearing corporations, the exchanges guarantee performance of the
contracts as between the clearing members of the exchange.
 
At the same time a Futures Contract is purchased or sold, the Fund must allocate
liquid assets as a deposit payment ("initial deposit"). The initial deposit
varies but may be as low as 5% or less of the value of the contract. Daily
thereafter, the Futures Contract is valued and the payment of "variation margin"
may be required since each day the Fund would provide or receive cash that
reflects any decline or increase in the contract's value.
 
At the time of delivery of securities pursuant to a Futures Contract based on
fixed income securities, adjustments are made to recognize differences in value
arising from the delivery of securities with a different interest rate from that
specified in the contract. In some (but not many) cases, securities called for
by a Futures Contract may not have been issued when the contract was written.
 
A Futures Contract based on an index of securities, such as a Municipal Bond
index Futures Contract, provides for a cash
 
                                        4
<PAGE>   98
 
payment, equal to the amount, if any, by which the value of the index at
maturity is above or below the value of the index at the time the contract was
entered into, times a fixed index "multiplier". The index underlying such a
Futures Contract is generally a broad based index of securities designed to
reflect movements in the relevant market as a whole. The index assigns weighted
values to the securities included in the index, and its composition is changed
periodically.
 
Although Futures Contracts call for the actual delivery or acquisition of
securities or, in the case of Futures Contracts based on an index, the making or
acceptance of a cash settlement at a specified future time, the contractual
obligation is usually fulfilled before such date by buying or selling, as the
case may be, on a commodities exchange, an identical Futures Contract calling
for settlement in the same month, subject to the availability of a liquid
secondary market. The Fund incurs brokerage fees when it purchases and sells
Futures Contracts.
 
One purpose of the acquisition or sale of a Futures Contract, in the case of a
portfolio such as that of the Fund, which holds or intends to acquire long-term
fixed income securities, is to attempt to protect the Fund from fluctuations in
interest rates without actually buying or selling long-term fixed income
securities. For example, if the Fund owns long-term bonds, and interest rates
were expected to increase, the Fund might enter into Futures Contracts for the
sale of debt securities. Such a sale would have much the same effect as selling
an equivalent value of the long-term bonds owned by the Fund. If interest rates
did increase, the value of the debt securities in the portfolio would decline,
but the value of the Futures Contracts would increase at approximately the same
rate, thereby keeping the net asset value of the Fund from declining as much as
it otherwise would have. The Fund could accomplish similar results by selling
bonds with long maturities and investing in bonds with short maturities when
interest rates are expected to increase. However, the use of Futures Contracts
as an investment technique allows the Fund to maintain a hedging position
without having to sell its portfolio securities.
 
Similarly, when it is expected that interest rates may decline, Futures
Contracts may be purchased to attempt to hedge against anticipated purchases of
long-term bonds at higher prices. Since the fluctuations in the value of Futures
Contracts should be similar to that of long-term bonds, the Fund could take
advantage of the anticipated rise in the value of long-term bonds without
actually buying them until the market had stabilized. At that time, the Futures
Contracts could be liquidated and the Fund could then buy long-term bonds on the
cash market. To the extent the Fund enters into Futures Contracts for this
purpose, the assets in the segregated asset account maintained to cover the
Fund's obligations with respect to such Futures Contracts will consist of liquid
assets from its portfolio in an amount equal to the difference between the
fluctuating market value of such Futures Contracts and the aggregate value of
the initial and variation margin payments made by the Fund with respect to such
Futures Contracts, thereby assuring that the positions are unleveraged.
 
The ordinary spreads between prices in the cash and futures markets, due to
differences in the natures of those markets, are subject to distortions. First,
all participants in the futures market are subject to initial deposit and
variation margin requirements. Rather than meeting additional variation margin
requirements, investors may close out Futures Contracts through offsetting
transactions which could distort the normal relationship between the cash and
futures markets. Second, the liquidity of the futures market depends on
participants entering into offsetting transactions rather than making or taking
delivery. To the extent participants decide to make or take delivery, liquidity
in the futures market could be reduced, thus producing distortion. Third, from
the point of view of speculators, the margin deposit requirements in the futures
market are less onerous than margin requirements in the securities market.
Therefore, increased participation by speculators in the futures market may
cause temporary price distortions. Due to the possibility of distortion, a
correct forecast of general interest rate trends by the Adviser may still not
result in a successful transaction.
 
In addition, Futures Contracts entail risks. Although the Fund believes that use
of such contracts will benefit the Fund, if the Adviser's investment judgment
about the general direction of interest rates is incorrect, the Fund's overall
performance would be poorer than if it had not entered into any such contract.
For example, if the Fund has hedged against the possibility of an increase in
interest rates which would adversely affect the price of bonds held in its
portfolio and interest rates decrease instead, the Fund will lose part or all of
the benefit of the increased value of its bonds which it has hedged because it
will have offsetting losses in its futures positions. In addition, in such
situations, if the Fund has insufficient cash, it may have to sell bonds from
its portfolio to meet daily variation margin requirements. Such sales of bonds
may be, but will not necessarily be, at increased prices which reflect the
rising market. The Fund may have to sell securities at a time when it may be
disadvantageous to do so. The Fund may invest in Future Contracts for hedging
and for non-hedging purposes, subject to applicable law.
 
  OPTIONS ON FUTURES CONTRACTS: The Fund may purchase and write options on
Futures Contracts ("Options on Futures Contracts") for hedging purposes and for
non-hedging purposes, subject to applicable law. An Option on a Futures Contract
provides the holder with the right to enter into a "long" position in the
underlying Futures Contract, in the case of a call option, or a "short" position
in the underlying Futures Contract, in the case of a put option, at a fixed
exercise price up to a stated expiration date or, in the case of certain
options, on such date. Such Options on Futures Contracts will be traded on
contract markets regulated by the CFTC. Depending on the pricing of the option
compared to either the price of the Futures Contract upon which it is based or
the price of the underlying debt securities, it may or may not be less risky
than ownership of the Futures Contract or underlying debt securities. As with
the purchase of Futures Contracts, when the Fund is not fully invested, it may
purchase a call Option on a Futures Contract to hedge against a market advance
due to declining interest rates.
 
                                        5
<PAGE>   99
 
The writing of a call Option on a Futures Contract constitutes a partial hedge
against declining prices of the securities which are deliverable upon exercise
of the Futures Contract. If the future price at expiration of the option is
below the exercise price, the Fund will retain the full amount of the option
premium which provides a partial hedge against any decline that may have
occurred in the Fund's portfolio holdings. The writing of a put Option on a
Futures Contract constitutes a partial hedge against increasing prices of the
securities which are deliverable upon exercise of the Futures Contract. If the
futures price at expiration of the option is higher than the exercise price, the
Fund will retain the full amount of the option premium, less related transaction
costs, which provides a partial hedge against any increase in the price of
securities which the Fund intends to purchase. If a put or call option the Fund
has written is exercised, the Fund will incur a loss which will be reduced by
the amount of the premium it receives, less related transaction costs. Depending
on the degree of correlation between changes in the value of its portfolio
securities and changes in the value of its futures positions, the Fund's losses
from existing Options on Futures Contracts may to some extent be reduced or
increased by changes in the value of portfolio securities. The writer of an
Option on a Futures Contract is subject to the requirement of initial and
variation margin payments.
 
   
The Fund may cover the writing of call Options on Futures Contracts (a) through
purchases of the underlying Futures Contract, (b) through ownership of the
security, or securities included in the index, underlying the Futures Contract,
or (c) through the holding of a call on the same Futures Contract and in the
same principal amount as the call written where the exercise price of the call
held (i) is equal to or less than the exercise price of the call written or (ii)
is greater than the exercise price of the call written if liquid assets
representing the difference are segregated by the Fund. The Fund may cover the
writing of put Options on Futures Contracts (a) through sales of the underlying
Futures Contract, (b) through segregation of liquid assets in an amount equal to
the value of the security or index underlying the Futures Contract, or (c)
through the holding of a put on the same Futures Contract and in the same
principal amount as the put written where the exercise price of the put held is
equal to or greater than the exercise price of the put written, or is less than
the exercise price of the put written if liquid assets representing the
difference are segregated by the Fund in liquid assets in a segregated account
with its custodian. Put and call Options on Futures Contracts written by the
Fund may also be covered in such other manner as may be in accordance with the
requirements of the exchange on which they are traded and applicable laws and
regulations.
    
 
The purchase of a put Option on a Futures Contract is similar in some respects
to the purchase of protective put options on portfolio securities. The Fund will
purchase a put Option on a Futures Contract to hedge the Fund's portfolio
against the risk of rising interest rates.
 
The amount of risk the Fund assumes when it purchases an Option on a Futures
Contract is the premium paid for the option plus related transaction costs,
although in order to realize a profit it may be necessary to exercise the option
and close out the underlying Futures Contract. In addition to the correlation
risks discussed above, the purchase of an option also entails the risk that
changes in the value of the underlying Futures Contract will not be fully
reflected in the value of the option purchased.
 
  ADDITIONAL RISKS OF OPTIONS ON FIXED INCOME SECURITIES, FUTURES CONTRACTS AND
OPTIONS ON FUTURES CONTRACTS: Various additional risks exist with respect to the
trading of options and Futures Contracts. For example, the Fund's ability
effectively to hedge all or a portion of its portfolio through transactions in
such instruments will depend on the degree to which price movements in the
underlying index or instrument correlate with price movements in the relevant
portion of the Fund's portfolio. The trading of futures and options entails the
additional risk of imperfect correlation between movements in the futures or
option price and the price of the underlying index or obligation, while the
trading of options also entails the risk of imperfect correlation between
securities used to cover options written and the securities underlying such
options. The anticipated spread between the prices may be distorted because of
various factors, which are set forth under "Futures Contracts" above.
 
The Fund's ability to engage in options and futures strategies will also depend
on the availability of liquid markets in such instruments. "Options" above sets
forth certain reasons why a liquid secondary market may not exist. Transactions
in these instruments are also subject to the risk of brokerage firm or clearing
house insolvencies.
 
The liquidity of a secondary market in a Futures Contract or option thereon may
be adversely affected by "daily price fluctuation limits", established by
exchanges, which limit the amount of fluctuation in the price of a contract
during a single trading day and prohibit trading beyond such limit. In addition,
the exchanges on which futures and options are traded may impose limitations
governing the maximum number of positions on the same side of the market and
involving the same underlying instrument which may be held by a single investor,
whether acting alone or in concert with others (regardless of whether such
contracts are held on the same or different exchanges or held or written in one
or more accounts or through one or more brokers).
 
Options on securities may be traded over-the-counter. In an over-the-counter
trading environment, many of the protections afforded to exchange participants
will not be available. For example, there are no clearing house performance
guarantees and the Fund will be subject to the risk of default by a counter
party. In addition, there are no daily price fluctuation limits, and adverse
market movements could therefore continue to an unlimited extent over a period
of time. Although the purchaser of an option cannot lose more than the amount of
the premium plus related transaction costs, this entire amount could be lost.
 
It should also be noted that the Fund may enter transactions in Futures
Contracts and Options on Futures Contracts not only for hedging purposes, but
also for non-hedging purposes intended to increase portfolio returns.
Non-hedging transactions in such investments involve greater risks and may
result in losses which
 
                                        6
<PAGE>   100
 
may not be offset by increases in the value of portfolio securities or declines
in the cost of securities to be acquired. The Fund will only write covered
options, such that liquid assets necessary to satisfy an option exercise will be
segregated at all times, unless the option is covered in such other manner as
may be in accordance with the rules of the exchange on which the option is
traded and applicable laws and regulations. Nevertheless, the method of covering
an option employed by the Fund may not fully protect it against risk of loss
and, in any event, the Fund could suffer losses on the option position which
might not be offset by corresponding portfolio gains.
 
  PORTFOLIO TRADING: The Fund intends to fully manage its portfolio by buying
and selling securities, as well as holding securities to maturity. In managing
its portfolio the Fund seeks to take advantage of market developments and yield
disparities, which may include use of the following strategies:
 
    (1) shortening the average maturity of its portfolio in anticipation of a
  rise in interest rates so as to minimize depreciation of principal;
 
    (2) lengthening the average maturity of its portfolio in anticipation of a
  decline in interest rates so as to maximize tax-exempt yield;
 
    (3) selling one type of debt security (e.g., revenue bonds) and buying
  another (e.g., general obligation bonds) when disparities arise in the
  relative values of each; and
 
    (4) changing from one debt security to an essentially similar debt security
  when their respective yields are distorted due to market factors.
                         ------------------------------
 
The investment objective and policies described above and the policies with
respect to portfolio trading described above may be changed without shareholder
approval.
 
INVESTMENT RESTRICTIONS. The Fund has adopted the following restrictions which
cannot be changed without the approval of the holders of a majority of the
Fund's shares (which, as used in this SAI, means the lesser of (i) more than 50%
of the outstanding shares of the Trust (or a class or series, as applicable) or
(ii) 67% or more of the outstanding shares of the Trust (or a class or series,
as applicable) present at a meeting at which holders of more than 50% of the
outstanding shares of the Trust (or a class or series, as applicable) are
represented in person or by proxy):
 
The Fund may not:
 
    (1) Borrow money, except as a temporary measure for extraordinary or
  emergency purposes, and then only in an amount not exceeding 10% of its gross
  assets, or pledge, mortgage or hypothecate an amount of its assets taken at
  market value which would exceed 15% of its gross assets, in each case taken at
  the lower of cost or market value and subject to a 300% asset coverage
  requirement (for the purpose of this restriction, collateral arrangements with
  respect to options, Futures Contracts and Options on Futures Contracts and
  payments of initial and variation margin in connection therewith are not
  considered a pledge of assets);
 
    (2) Underwrite securities issued by other persons except insofar as the Fund
  may technically be deemed an underwriter under the Securities Act of 1933 in
  selling a portfolio security;
 
    (3) Purchase or sell real estate (including limited partnership interests
  but excluding Municipal Bonds secured by real estate or interests therein),
  interests in oil, gas or mineral leases, commodities or commodity contracts
  (except Futures Contracts and Options on Futures Contracts) in the ordinary
  course of its business;
 
    (4) Make loans to other persons except through the use of repurchase
  agreements or the purchase of commercial paper. Not more than 10% of its total
  assets will be invested in repurchase agreements maturing in more than seven
  days. For these purposes the purchase of a portion of an issue of debt
  securities which is part of an issue to the public shall not be considered the
  making of a loan;
 
    (5) Purchase the securities of any issuer if such purchase, at the time
  thereof, would cause more than 5% of its total assets taken at market value to
  be invested in the securities of such issuer, other than securities issued or
  guaranteed by the U.S. Government or its agencies or instrumentalities, or
  invest more than 25% of its total assets taken at market value in securities
  of issuers in any one industry;
 
    (6) Purchase or retain in its portfolio any securities issued by an issuer
  any of whose officers, directors, trustees or security holders is an officer
  or Trustee of the Trust, or is a member, partner, officer or Director of the
  Adviser, if after the purchase of the securities of such issuer by the Fund
  one or more of such persons owns beneficially more than 1/2 of 1% of the
  shares or securities, or both, all taken at market value, of such issuer, and
  such persons owning more than 1/2 of 1% of such shares or securities together
  own beneficially more than 5% of such shares or securities, or both, all taken
  at market value;
 
    (7) Purchase any securities or evidences of interest therein on margin,
  except that the Fund may obtain such short-term credit as may be necessary for
  the clearance of purchases and sales of securities and except that the Fund
  may make deposits on margin in connection with options, Futures Contracts and
  Options on Futures Contracts;
 
    (8) Sell any security which the Fund does not own unless by virtue of its
  ownership of other securities it has at the time of sale a right to obtain
  securities without payment of further consideration equivalent in kind and
  amount to the securities sold and provided that if such right is conditional
  the sale is made upon the same conditions; or
 
    (9) Purchase or sell any put or call option or any combination thereof,
  provided that this shall not prevent the writing, purchasing and selling of
  puts, calls or combinations thereof with respect to securities and Futures
  Contracts.
 
As a matter of non-fundamental policy, the Fund may not invest in securities
(other than repurchase agreements maturing in seven days or less) which are
subject to legal or contractual restrictions on resale or for which there is no
readily available
 
                                        7
<PAGE>   101
 
market (unless the Board of Trustees has determined that such securities are
liquid based upon trading markets for the specific security) if more than 15% of
the Fund's assets would be invested in such securities. As an additional matter
of non-fundamental policy, the Fund may not invest 25% or more of the market
value of its total assets in securities of issuers in any one industry.
 
For the purposes of the Fund's investment restrictions, the issuer of a
tax-exempt security is deemed to be the entity (public or private) ultimately
responsible for the payment of the principal of and interest on the security.
 
Except with respect to Investment Restriction (1) and the Fund's non-fundamental
policy on investing in illiquid securities, these investment restrictions and
policies are adhered to at the time of purchase or utilization of assets; a
subsequent change in circumstances will not be considered to result in a
violation of policy.
 
3.   MANAGEMENT OF THE FUND
The Trust's Board of Trustees provides broad supervision over the affairs of the
Fund. The Adviser is responsible for the management of the Fund's assets and the
officers of the Trust are responsible for the Fund's operations. The Trustees
and officers are listed below, together with their principal occupations during
the past five years. (Their titles may have varied during that period.)
 
TRUSTEES
   
RICHARD B. BAILEY* (born 9/14/26)
    
Private Investor; Massachusetts Financial Services Company, former Chairman and
  Director (prior to September 30, 1991); Cambridge Bancorp, Director; Cambridge
  Trust Company, Director
 
PETER G. HARWOOD (born 4/3/26)
Private Investor
Address: 211 Lindsay Pond Road, Concord, Massachusetts
 
J. ATWOOD IVES (born 5/1/36)
   
Eastern Enterprises (diversified services company), Chairman, Trustee and Chief
  Executive Officer
    
Address: 9 Riverside Road, Weston, Massachusetts
 
LAWRENCE T. PERERA (born 6/23/35)
Hemenway & Barnes (attorneys), Partner
Address: 60 State Street, Boston, Massachusetts
 
WILLIAM J. POORVU (born 4/10/35)
Harvard University Graduate School of Business Administration, Adjunct
  Professor; CBL & Associates Properties, Inc. (a real estate investment trust),
  Director; The Baupost Fund (a registered investment company), Vice Chairman
  (since November 1993), Chairman and Trustee (prior to November 1993)
Address: Harvard Business School, Soldiers Field Road, Cambridge, Massachusetts
 
CHARLES W. SCHMIDT (born 3/18/28)
   
Private Investor; International Technology Corporation, Director; Mohawk Paper
  Company, Director
    
Address: 30 Colpitts Road, Weston, Massachusetts
 
ARNOLD D. SCOTT* (born 12/16/42)
Massachusetts Financial Services Company, Senior Executive Vice President,
  Secretary and Director
 
JEFFREY L. SHAMES* (born 6/2/55)
   
Massachusetts Financial Services Company, Chairman and Chief Executive Officer
    
 
ELAINE R. SMITH (born 4/25/46)
Independent Consultant
   
Address: Weston, Massachusetts
    
 
DAVID B. STONE (born 9/2/27)
North American Management Corp. (investment adviser), Chairman and Director;
  Eastern Enterprises, Trustee
Address: 10 Post Office Square, Suite 300, Boston, Massachusetts
 
OFFICERS
W. THOMAS LONDON,* Treasurer (born 3/1/44)
Massachusetts Financial Services Company, Senior Vice President
 
STEPHEN E. CAVAN,* Secretary and Clerk (born 11/6/53)
Massachusetts Financial Services Company, Senior Vice President, General Counsel
  and Assistant Secretary
 
JAMES R. BORDEWICK, JR.,* Assistant Secretary (born
  3/6/59)
Massachusetts Financial Services Company, Senior Vice President and Associate
  General Counsel
 
   
GEOFFREY L. KURINSKY,* Vice President (born 7/7/53)
    
Massachusetts Financial Services Company, Senior Vice President
 
JAMES O. YOST,* Assistant Treasurer (born 6/12/60)
Massachusetts Financial Services Company, Vice President
 
MARK E. BRADLEY,* Assistant Treasurer (born 11/23/59)
Massachusetts Financial Services Company, Vice President (since March 1997);
  Putnam Investments, Vice President (from September 1994 until March 1997);
  Ernst & Young, Senior Tax Manager (until September 1994)
 
   
ELLEN MOYNIHAN,* Assistant Treasurer (born 11/13/57)
    
Massachusetts Financial Services Company, Vice President (since September 1996);
  Deloltte & Touche LLP, Senior Manager (until September 1996)
- ---------------
 
*"Interested persons" (as defined in the Investment Company Act of 1940 (the
 "1940 Act") of the Adviser, whose address is 500 Boylston Street, Boston,
 Massachusetts 02116.
 
   
Each Trustee and officer holds comparable positions with certain MFS affiliates
or with certain other funds of which MFS or a subsidiary of MFS is the
investment adviser or distributor. Messrs. Shames, Scott, and Cavan, are the
Chairman, a Director and the Secretary, respectively of MFD and hold similar
positions with certain other MFS affiliates. Mr. Bailey is a Director of Sun
Life Assurance Company of Canada (U.S.), a subsidiary of Sun Life Assurance
Company of Canada ("Sun Life").
    
 
The Fund pays the compensation of non-interested Trustees and Mr. Bailey (who
currently receive a fee of $4,000 per year plus $180 per meeting and $150 per
committee meeting attended, together with such Trustee's out-of-pocket expenses)
and has adopted a retirement plan for non-interested Trustees and Mr. Bailey.
Under this plan, a Trustee will retire upon reaching age 73 and if the Trustee
has completed at least five years of service, he would be entitled to annual
payments during his lifetime of up to 50% of such Trustee's average annual
compensation (based on the three years prior to his retirement) depending on his
length of service. A Trustee may also retire prior to age 73 and receive reduced
payments if he has completed at least five years of service. Under the plan, a
Trustee (or his beneficiaries) will also receive benefits for a period of time
in the event the Trustee is disabled or dies. These benefits will also be based
on the Trustee's average annual
 
                                        8
<PAGE>   102
 
   
compensation and length of service. There is no retirement plan provided by the
Trust for Messrs. Scott and Shames. The Fund will accrue its allocable share of
compensation expenses each year to cover current year's service and amortize
past service cost.
    
 
                           TRUSTEE COMPENSATION TABLE
 
   
<TABLE>
<CAPTION>
                                                                      RETIREMENT BENEFIT                     TOTAL TRUSTEE
                                                       TRUSTEE FEES       ACCRUED AS         ESTIMATED         FEES FROM
                                                           FROM          PART OF FUND      CREDITED YEARS      FUND AND
                       TRUSTEE                           FUND(1)          EXPENSE(1)       OF SERVICE(2)    FUND COMPLEX(3)
                       -------                         ------------   ------------------   --------------   ---------------
<S>                                                    <C>            <C>                  <C>              <C>
Richard B. Bailey....................................     $6,307            $2,466                8            $242,022
Peter G. Harwood.....................................      7,477             1,937                5             121,105
J. Atwood Ives.......................................      6,427             2,489               17             108,720
Lawrence T. Perera...................................      6,457             3,740               26             127,055
William Poorvu.......................................      6,937             3,840               25             121,105
Charles W. Schmidt...................................      6,397             3,815               20             121,105
Arnold D. Scott......................................          0                 0              N/A                   0
Jeffrey L. Shames....................................          0                 0              N/A                   0
Elaine R. Smith......................................      7,447             2,733               27             132,035
David B. Stone.......................................      7,537             3,610               11             127,055
</TABLE>
    
 
- ---------------
 
   
(1) For fiscal year ended August 31, 1998.
    
 
(2) Based on normal retirement age of 73. See the table below for the estimated
     annual benefits payable upon retirement by the Fund to a Trustee based on
     his or her estimated credited years of service.
 
   
(3) For calendar year 1997. All Trustees receiving compensation served as
     Trustees of 27 funds within the MFS fund complex (having aggregate net
     assets at December 31, 1997, of approximately $29 billion) except Mr.
     Bailey, who served as Trustee of 69 funds within the MFS fund complex
     (having aggregate net assets at December 31, 1997, of approximately $47.8
     billion).
    
          ESTIMATED ANNUAL BENEFITS PAYABLE BY FUND UPON RETIREMENT(4)
 
   
<TABLE>
<CAPTION>
                                YEARS OF SERVICE
  AVERAGE        ----------------------------------------------
TRUSTEE FEES       3           5           7         10 OR MORE
- ------------       -           -           -         ----------
<S>              <C>         <C>         <C>         <C>
   $5,676        $  851      $1,419      $1,987        $2,838
    6,199           930       1,550       2,170         3,100
    6,722         1,008       1,681       2,353         3,361
    7,245         1,087       1,811       2,536         3,622
    7,768         1,165       1,942       2,719         3,884
    8,291         1,244       2,073       2,902         4,145
</TABLE>
    
 
- ---------------
 
(4) Other funds in the MFS fund complex provide similar retirement benefits to
     the Trustees.
 
   
As of October 30, 1998, all Trustees and officers as a group owned less than 1%
of the outstanding shares of the Fund.
    
 
   
As of October 30, 1998, Merrill Lynch, Pierce, Fenner & Smith Inc., 4800 Deer
Lake Drive East, Jacksonville, FL 32246 was the record holder of approximately
8.08% of the outstanding Class B shares of the Fund.
    
 
The Trust's Declaration of Trust provides that it will indemnify its Trustees
and officers against liabilities and expenses incurred in connection with
litigation in which they may be involved because of their offices with the
Trust, unless, as to liabilities to the Trust or its shareholders, it is finally
adjudicated that they engaged in willful misfeasance, bad faith, gross
negligence or reckless disregard of the duties involved in their offices, or
with respect to any matter, unless it is adjudicated that they did not act in
good faith in the reasonable belief that their actions were in the best interest
of the Trust. In the case of settlement, such indemnification will not be
provided unless it has been determined pursuant to the Declaration of Trust that
such officers or Trustees have not engaged in willful misfeasance, bad faith,
gross negligence or reckless disregard of their duties.
 
INVESTMENT ADVISER
   
MFS and its predecessor organizations have a history of money management dating
from 1924. MFS is a subsidiary of Sun Life of Canada (U.S.) Financial Services
Holdings, Inc. which in turn is an indirect wholly owned subsidiary of Sun Life.
    
 
The Adviser manages the Fund pursuant to an Investment Advisory Agreement, dated
September 1, 1993 (the "Advisory Agreement"). Under the Advisory Agreement, the
Adviser provides the Fund with overall investment advisory services. Subject to
such policies as the Trustees may determine, the Adviser makes investment
decisions for the Fund. For these services and facilities, the Adviser receives
a management fee computed and paid monthly on the basis of a formula based upon
a percentage of the Fund's average daily net assets plus a percentage of its
gross income (i.e., income other than gains
 
                                        9
<PAGE>   103
 
from the sale of securities) in each case on an annualized basis for the Fund's
then current fiscal year. The applicable percentages are reduced as assets and
income reach the following levels:
 
<TABLE>
<CAPTION>
  ANNUAL RATE OF MANAGEMENT FEE     ANNUAL RATE OF MANAGEMENT FEE
BASED ON AVERAGE DAILY NET ASSETS       BASED ON GROSS INCOME
- ---------------------------------   -----------------------------
<S>                                <C>
 .220% of the first $200 million    4.12% of the first $16 million
 .187% of average daily net assets  3.51% of gross income in excess
  in excess of $200 million        of $16 million
 .168% of average daily net assets  3.16% of gross income in excess
  in excess of $2 billion          of $160 million
</TABLE>
 
   
For the Fund's fiscal years ended August 31, 1998, August 31, 1997 and August
31, 1996, MFS received management fees of $6,706,665 (equivalent to an annual
rate of 0.40% of average daily net assets), $7,363,899 (equivalent to an annual
rate of 0.40% of average daily net assets) and $7,990,167 (equivalent to an
annual rate of 0.40% of average daily net assets), respectively.
    
 
   
The Fund pays all of its expenses (other than those assumed by MFS or MFD),
including: Trustees fees discussed above; governmental fees; interest charges;
taxes; membership dues in the Investment Company Institute allocable to the
Fund; fees and expenses of independent auditors, of legal counsel, and of any
transfer agent, registrar or dividend disbursing agent of the Fund; expenses of
repurchasing and redeeming shares; expenses of preparing, printing and mailing
share certificates, shareholder reports, notices, proxy statements and reports
to governmental officers and commissions; brokerage and other expenses connected
with the execution, recording and settlement of portfolio security transactions;
insurance premiums; fees and expenses of State Street Bank and Trust Company,
the Fund's custodian, for all services to the Fund, including safekeeping of
funds and securities and maintaining required books and accounts; expenses of
calculating the net asset value of the Fund's shares; and expenses of
shareholder meetings. Expenses relating to the issuance, registration and
qualification of shares of the Fund and the preparation, printing and mailing of
prospectuses for such purposes are borne by the Fund except that its
Distribution Agreement with MFD requires MFD to pay for prospectuses which are
to be used for sales purposes. For a list of the Fund's expenses, including the
compensation paid to the Trustees who are not officers of the Fund, during the
Fund's fiscal year ended August 31, 1998, see "Financial Statements -- Statement
of Operations" in the Annual Report.
    
 
   
MFS pays the compensation of the Trust's officers and of any Trustee who is an
officer of MFS. The Adviser also furnishes at its own expense all necessary
administrative services, including office space, equipment, clerical personnel,
investment advisory facilities, and all executive and supervisory personnel
necessary for managing the Fund's investments, effecting the Fund's portfolio
transactions.
    
 
   
The Advisory Agreement will remain in effect until August 1, 1999, and will
continue in effect thereafter only if such continuance is specifically approved
at least annually by the Board of Trustees or by vote of a majority of the
Fund's outstanding voting securities (as defined under "Investment
Restrictions") and, in either case, by a majority of the Trustees who are not
parties to the Advisory Agreement or interested persons of any such party. The
Advisory Agreement terminates automatically if it is assigned and may be
terminated without penalty by vote of a majority of the Fund's shares (as
defined in "Investment Restrictions") or by either party on not more than 60
days' nor less than 30 days' written notice. The Advisory Agreement provides
that if MFS ceases to serve as Adviser to the Fund, the Fund will change its
name so as to delete the initials "MFS." The Advisory Agreement further provides
that MFS may render services to others and may permit fund clients in addition
to the Fund to use the initials "MFS" in their names. The Advisory Agreement
also provides that neither MFS nor its personnel shall be liable for any error
of judgment or mistake of law or for any loss arising out of any investment or
for any act or omission in the execution and management of the Fund, except for
willful misfeasance, bad faith or gross negligence in the performance of its or
their duties or by reason of reckless disregard of its or their obligations and
duties under the Advisory Agreement.
    
 
ADMINISTRATOR
   
MFS provides the Fund with certain financial, legal, compliance, shareholder
communications and other administrative services pursuant to a Master
Administrative Services Agreement dated March 1, 1997, as amended. Under the
Agreement, the Fund pays MFS an administrative fee up to 0.015% per annum of the
Fund's average daily net assets. This fee reimburses MFS for a portion of the
costs it incurs to provide such services. For the period from March 1, 1997
through August 31, 1997, and the fiscal year ended August 31, 1998 MFS received
fees under the Agreement of $124,924 and $225,937, respectively.
    
 
CUSTODIAN
   
State Street Bank and Trust Company (the "Custodian") is the custodian of the
Fund's assets. The Custodian's responsibilities include: safekeeping and
controlling the Fund's cash and securities, handling the receipt and delivery of
securities, determining income and collecting interest and dividends on the
Fund's investments, maintaining books of original entry for portfolio and fund
accounting and other required books and accounts, and calculating the daily net
asset value of each class of shares of the Fund. The Custodian does not
determine the investment policies of the Fund or decide which securities the
Fund will buy or sell. The Fund may, however, invest in securities, including
repurchase agreements, issued by the Custodian and may deal with the Custodian
as principal in securities transactions. The Custodian also acts as the dividend
disbursing agent for the Fund.
    
 
SHAREHOLDER SERVICING AGENT
MFS Service Center, Inc. (the "Shareholder Servicing Agent"), a wholly owned
subsidiary of MFS, is the Fund's shareholder servicing agent, pursuant to a
Shareholder Servicing Agreement, effective August 1, 1985, as amended (the
"Agency Agreement") with the Fund. The Shareholder Servicing Agent's
responsibilities under the Agency Agreement include administering and performing
transfer agent functions and keeping records in connection with the issuance,
transfer and redemption of each
 
                                       10
<PAGE>   104
 
   
class of shares of the Fund. For these services, the Shareholder Servicing Agent
receives a fee calculated as a percentage of the average daily net assets of an
effective rate of 0.1125%. In addition, the Shareholder Servicing Agent is
reimbursed by the Fund for certain expenses incurred by the Shareholder
Servicing Agent on behalf of the Fund. State Street Bank and Trust Company, the
dividend disbursing agent of the Fund, has contracted with the Shareholder
Servicing Agent to administer and perform certain dividend and distribution
disbursing agent functions for the Fund.
    
 
DISTRIBUTOR
   
MFD, a wholly owned subsidiary of MFS, serves as distributor for the continuous
offering of shares of the Fund pursuant to a distribution agreement dated
January 1, 1995 (the "Distribution Agreement").
    
 
CLASS A SHARES: MFD acts as agent in selling Class A shares of the Fund to
dealers. The public offering price of Class A shares of the Fund is their net
asset value next computed after the sale plus a sales charge which varies based
upon the quantity purchased. The public offering price of Class A shares of the
Fund is calculated by dividing the net asset value of a Class A share by the
difference (expressed as a decimal) between 100% and the sales charge percentage
of offering price applicable to the purchase (see "Purchases" in the
Prospectus). The sales charge scale set forth in the Prospectus applies to
purchases of Class A shares of the Fund alone or in combination with shares of
all classes of certain other funds in the MFS Family of Funds (the "MFS Funds")
and other funds (as noted under Right of Accumulation) by any person, including
members of a family unit (e.g., husband, wife and minor children) and bona fide
trustees, and also applies to purchases made under the Right of Accumulation or
a Letter of Intent (see "Investment and Withdrawal Programs"). A group might
qualify to obtain quantity sales charge discounts (see "Investment and
Withdrawal Programs").
 
Class A shares of the Fund may be sold at their net asset value to certain
persons and in certain instances as described in the Prospectus. Such sales are
made without a sales charge to promote good will with employees and others with
whom MFS, MFD and/or the Fund have business relationships, and because the sales
effort, if any, involved in making such sales is negligible.
 
MFD allows discounts to dealers (which are alike for all dealers) from the
applicable public offering price of the Class A shares. Dealer allowances
expressed as a percentage of offering price for all offering prices are set
forth in the Prospectus (see "Purchases" in the Prospectus). The difference
between the total amount invested and the sum of (a) the net proceeds to the
Fund and (b) the dealer commission, is the commission paid to the distributor.
Because of rounding in the computation of offering price, the portion of the
sales charge paid to the underwriter may vary and the total sales charge may be
more or less than the sales charge calculated using the sales charge expressed
as a percentage of offering price or as a percentage of the net amount invested
as listed in the Prospectus. In the case of the maximum sales charge, the dealer
retains 4% and MFD retains approximately 3/4 of 1% of the public offering price.
In addition, MFD pays a commission to dealers who initiate and are responsible
for purchases of $1 million or more as described in the Prospectus.
 
CLASS B SHARES: MFD acts as agent in selling Class B shares of the Fund. The
public offering price of Class B shares is their net asset value next computed
after the sale (see "Purchases" in the Prospectus).
 
GENERAL: Neither MFD nor dealers are permitted to delay placing orders to
benefit themselves by a price change. On occasion, MFD may obtain brokers loans
from various banks, including the custodian banks for the MFS Funds, to
facilitate the settlement of sales of shares of the Fund to dealers. MFD may
benefit from its temporary holding of funds paid to it by investment dealers for
the purchase of Fund shares.
 
   
During the Fund's fiscal year ended August 31, 1998, MFD and certain other
financial institutions received net commissions of $235,283 and $8,723,087,
respectively (as their concession on gross commissions of $8,958,370. The Fund
received $45,795,624, representing the aggregate net asset value of such shares.
During the Fund's fiscal year ended August 31, 1997, MFD and certain other
financial institutions received net commissions of $185,845 and $1,217,830,
respectively (as their concession on gross commissions of $1,403,675). The Fund
received $138,735,228, representing the aggregate net asset value of such
shares. During the Fund's fiscal year ended August 31, 1996, MFD and certain
other financial institutions received net commissions of $289,161 and
$1,953,785, respectively (as their concession on gross commissions of
$2,242,946). The Fund received $179,674,142, representing the aggregate net
asset value of such shares.
    
 
   
The Distribution Agreement will remain in effect until August 1, 1999, and will
continue in effect thereafter only if such continuance is specifically approved
at least annually by the Board of Trustees or by vote of a majority of the
Trust's shares (as defined in "Investment Restrictions") and, in either case, by
a majority of the Trustees who are not parties to the Distribution Agreement or
interested persons of any such party. The Distribution Agreement terminates
automatically if it is assigned and may be terminated without penalty by either
party on not more than 60 days' nor less than 30 days' notice.
    
 
   
During the Fund's fiscal year ended August 31, 1998, the CDSC imposed upon the
redemption of Class A and Class B shares was $14,689 and $188,693, respectively.
During the Fund's fiscal year ended August 31, 1997, the CDSC imposed upon the
redemption of Class A and Class B shares was $9,427 and $10,251, respectively.
During the Fund's fiscal year ended August 31, 1996, the CDSC imposed upon the
redemption of Class A and Class B shares was $1,862 and $186,111, respectively.
    
 
                                       11
<PAGE>   105
 
4.   PORTFOLIO TRANSACTIONS AND BROKERAGE COMMISSIONS
Specific decisions to purchase or sell securities for the Fund are made by a
portfolio committee, consisting of employees of the Adviser who are appointed
and supervised by its senior officers. Changes in the Fund's investments are
reviewed by the Board of Trustees. Members of the Fund's portfolio committee may
serve other clients of the Adviser or any subsidiary of the Adviser in a similar
capacity.
 
The primary consideration in placing portfolio security transactions is
execution at the most favorable price. The Adviser has complete freedom as to
the markets in and broker-dealers through which it seeks this result. Municipal
Bonds and other debt securities are traded principally in the over-the-counter
market on a net basis through dealers acting for their own account and not as
brokers. The cost of securities purchased from underwriters includes an
underwriter's commission or concession, and the prices at which securities are
purchased and sold from and to dealers include a dealer's mark-up or mark-down.
The Adviser attempts to negotiate with underwriters to decrease the commission
or concession for the benefit of the Fund. The Adviser normally seeks to deal
directly with the primary market makers unless, in its opinion, better prices
are available elsewhere. Securities firms or futures commission merchants may
receive brokerage commissions on transactions involving Futures Contracts and
Options on Futures Contracts. Subject to the requirement of seeking execution at
the best available price, securities may, as authorized by the Advisory
Agreement, be bought from or sold to dealers who have furnished statistical,
research and other information or services to the Adviser. At present no
arrangements for the recapture of commission payments are in effect.
 
Consistent with the foregoing primary consideration, the Conduct Rules of the
NASD and such other policies as the Trustees may determine, the Adviser may
consider sales of shares of the Fund and of the other investment company clients
of MFD as a factor in the selection of broker-dealers to execute the Fund's
portfolio transactions.
 
   
For the fiscal years ended August 31, 1998, 1997 and 1996, the Fund paid no
brokerage commissions.
    
 
In certain instances there may be securities which are suitable for the Fund's
portfolio as well as for that of one or more of the other clients of the Adviser
or any subsidiary of the Adviser. Investment decisions for the Fund and for such
other clients are made with a view to achieving their respective investment
objectives. It may develop that a particular security is bought or sold for only
one client even though it might be held by, or bought or sold for, other
clients. Likewise, a particular security may be bought for one or more clients
when one or more other clients are selling that same security. Some simultaneous
transactions are inevitable when several clients receive investment advice from
the same investment adviser, particularly when the same security is suitable for
the investment objectives of more than one client. When two or more clients are
simultaneously engaged in the purchase or sale of the same security, the
securities are allocated among clients in a manner believed by the Adviser to be
equitable to each. It is recognized that in some cases this system could have a
detrimental effect on the price or volume of the security as far as the Fund is
concerned. In other cases, however, the Fund believes that its ability to
participate in volume transactions will produce better executions for the Fund.
 
5.   SHAREHOLDER SERVICES
INVESTMENT AND WITHDRAWAL PROGRAMS -- The Fund makes available the following
programs designed to enable shareholders to add to their investment or withdraw
from it with a minimum of paper work. These are described below and, in certain
cases, in the Prospectus. The programs involve no extra charge to shareholders
(other than a sales charge in the case of certain Class A share purchases) and
may be changed or discontinued at any time by a shareholder or the Fund.
 
  LETTER OF INTENT: If a shareholder (other than a group purchaser described
below) anticipates purchasing $100,000 or more of Class A shares of the Fund
alone or in combination with shares of either class of other MFS Funds or MFS
Fixed Fund (a bank collective investment fund) within a 13-month period (or
36-month period, in the case of purchases of $1 million or more), the
shareholder may obtain Class A shares of the Fund at the same reduced sales
charge as though the total quantity were invested in one lump sum by completing
the Letter of Intent section of the Fund's Account Application or filing a
separate Letter of Intent application (available from the Shareholder Servicing
Agent) within 90 days of the commencement of purchases. Subject to acceptance by
MFD and the conditions mentioned below, each purchase will be made at a public
offering price applicable to a single transaction of the dollar amount specified
in the Letter of Intent application. The shareholder or his dealer must inform
MFD that the Letter of Intent is in effect each time shares are purchased. The
shareholder makes no commitment to purchase additional shares, but if his
purchases within 13 months (or 36 months, in the case of purchases of $1 million
or more), plus the value of shares credited toward completion of the Letter of
Intent do not total the sum specified, he will pay the increased amount of the
sales charge as described below. Instructions for issuance of shares in the name
of a person other than the person signing the Letter of Intent application must
be accompanied by a written statement from the dealer stating that the shares
were paid for by the person signing such Letter. Neither income dividends nor
capital gain distributions taken in additional shares will apply toward the
completion of the Letter of Intent. Dividends and distributions of other MFS
Funds automatically reinvested in shares of the Fund pursuant to the
Distribution Investment Program will also not apply toward completion of the
Letter of Intent.
 
Out of the shareholder's initial purchase (or subsequent purchases if
necessary), 5% of the dollar amount specified in the Letter of Intent
application shall be held in escrow by the Shareholder Servicing Agent in the
form of shares registered in the shareholder's name. All income dividends and
capital gain distributions on escrowed shares will be paid to the shareholder
 
                                       12
<PAGE>   106
 
or to his order. When the minimum investment so specified is completed (either
prior to or by the end of the 13-month period or 36-month period, as
applicable), the shareholder will be notified and the escrowed shares will be
released.
 
If the intended investment is not completed, the Shareholder Servicing Agent
will redeem an appropriate number of the escrowed shares in order to realize
such difference. Shares remaining after any such redemption will be released by
the Shareholder Servicing Agent. By completing and signing the Account
Application or separate Letter of Intent application, the shareholder
irrevocably appoints the Shareholder Servicing Agent his attorney to surrender
for redemption any or all escrowed shares with full power of substitution in the
premises.
 
  RIGHT OF ACCUMULATION: A shareholder qualifies for cumulative quantity
discounts on the purchase of Class A shares when that shareholder's new
investment, together with the current offering price value of all the holdings
of Class A, Class B and Class C shares of that shareholder in the MFS Funds or
MFS Fixed Fund (a bank collective investment fund) reaches a discount level (see
"Purchases" in the Prospectus for the sales charges on quantity discounts). For
example, if a shareholder owns shares valued at $75,000 and purchases $25,000 of
Class A shares of the Fund, the sales charge for the $25,000 purchase would be
at the rate of 4% (the rate applicable to single transactions of $100,000). A
shareholder must provide the Shareholder Servicing Agent (or his investment
dealer must provide MFD) with information to verify that the quantity sales
charge discount is applicable at the time the investment is made.
 
  SUBSEQUENT INVESTMENT BY TELEPHONE: Each shareholder may purchase additional
shares of any MFS Fund by telephoning the Shareholder Servicing Agent toll-free
at (800) 225-2606. The minimum purchase amount is $50 and the maximum purchase
amount is $100,000. Shareholders wishing to avail themselves of this telephone
purchase privilege must so elect on their Account Application and designate
thereon a bank and account number from which purchases will be made. If a
telephone purchase request is received by the Shareholder Servicing Agent on any
business day prior to the close of regular trading on the Exchange (generally,
4:00 p.m., Eastern time), the purchase will occur at the closing net asset value
of the shares purchased on that day. The Shareholder Servicing Agent may be
liable for any losses resulting from unauthorized telephone transactions if it
does not follow reasonable procedures designed to verify the identity of the
caller. The Shareholder Servicing Agent will request personal or other
information from the caller, and will normally also record calls. Shareholders
should verify the accuracy of confirmation statements immediately after their
receipt.
 
  DISTRIBUTION INVESTMENT PROGRAM: Distributions of dividends and capital gains
made by the Fund with respect to a particular class of shares may be
automatically invested in shares of the same class of shares of one of the other
MFS Funds, if shares of the fund are available for sale. Such investments will
be subject to additional purchase minimums. Distributions will be invested at
net asset value (exclusive of any sales charge) and will not subject to any
CDSC). Distributions will be invested at the close of business on the payable
date for the distribution. A shareholder considering the Distribution Investment
Program should obtain and read the prospectus of the other fund and consider the
differences in objectives and policies before making any investment.
 
  SYSTEMATIC WITHDRAWAL PLAN: A shareholder may direct the Shareholder Servicing
Agent to send him (or anyone he designates) regular periodic payments based upon
the value of his account. Each payment under a Systematic Withdrawal Plan (a
"SWP") must be at least $100, except in certain limited circumstances. The
aggregate withdrawals of Class B shares in any year pursuant to a SWP generally
are limited to 10% of the value of the account at the time of establishment of
the SWP. SWP payments are drawn from the proceeds of share redemptions (which
would be a return of principal and, if reflecting a gain, would be taxable).
Redemptions of Class B shares will be made in the following order: (i) any "Free
Amount"; (ii) to the extent necessary, any "Reinvested Shares"; and (iii) to the
extent necessary, the "Direct Purchase" subject to the lowest CDSC (as such
terms are defined in "Contingent Deferred Sales Charge" in the Prospectus). The
CDSC will be waived in the case of redemptions of Class B shares pursuant to a
SWP, but will not be waived in the case of SWP redemptions of Class A shares
which are subject to a CDSC. To the extent that redemptions for such periodic
withdrawals exceed dividend income reinvested in the account, such redemptions
will reduce and may eventually exhaust the number of shares in the shareholder's
account. All dividend and capital gain distributions for an account with a SWP
will be reinvested in additional, full or fractional shares of the Fund at the
net asset value in effect at the close of business on the record date for such
distributions. To initiate this service, shares having an aggregate value of at
least $5,000 either must be held on deposit by, or certificates for such shares
must be deposited with, the Shareholder Servicing Agent. With respect to Class A
shares, maintaining a withdrawal plan concurrently with an investment program
would be disadvantageous because of the sales charges included in share
purchases and the imposition of a CDSC on certain redemptions. The shareholder
may deposit into the account additional shares of the Fund, change the payee or
change the dollar amount of each payment. The Shareholder Servicing Agent may
charge the account for services rendered and expenses incurred beyond those
normally assumed by the Fund with respect to the liquidation of shares. No
charge is currently assessed against the account, but one could be instituted by
the Shareholder Servicing Agent on 60 days' notice in writing to the shareholder
in the event that the Fund ceases to assume the cost of these services. The Fund
may terminate any SWP for an account if the value of the account falls below
$5,000 as a result of share redemptions (other than as a result of a SWP) or an
exchange of shares of the Fund for shares of another MFS Fund. Any SWP may be
terminated at any time by either the shareholder or the Fund.
 
  INVEST BY MAIL: Additional investments of $50 or more may be made at any time
by mailing a check payable to the Fund directly to the Shareholder Servicing
Agent. The shareholder's
 
                                       13
<PAGE>   107
 
account number and the name of his investment dealer must be included with each
investment.
 
  GROUP PURCHASES: A bona fide group and all its members may be treated as a
single purchaser and, under the Right of Accumulation (but not a Letter of
Intent), obtain quantity sales charge discounts on the purchase of Class A
shares if the group (1) gives its endorsement or authorization to the investment
program so it may be used by the investment dealer to facilitate solicitation of
the membership, thus effecting economies of sales effort; (2) has been in
existence for at least six months and has a legitimate purpose other than to
purchase mutual fund shares at a discount; (3) is not a group of individuals
whose sole organizational nexus is as credit cardholders of a company,
policyholders of an insurance company, customers of a bank or broker-dealer,
clients of an investment adviser or other similar groups; and (4) agrees to
provide certification of membership of those members investing money in the MFS
Funds upon the request of MFD.
 
  AUTOMATIC EXCHANGE PLAN: Shareholders having account balances of at least
$5,000 in any MFS Fund may exchange their shares for the same class of shares of
the other MFS Funds, if available for sale, under the Automatic Exchange Plan.
The Automatic Exchange Plan provides for automatic exchanges of funds from the
shareholder's account in an MFS Fund for investment in the same class of shares
of other MFS Funds selected by the shareholder. Under the Automatic Exchange
Plan, exchanges of at least $50 each may be made to up to six different funds
effective on the seventh day of each month or of every third month, depending
whether monthly or quarterly exchanges are elected by the shareholder. If the
seventh day of the month is not a business day, the transaction will be
processed on the next business day. Generally, the initial exchange will occur
after receipt and processing by the Shareholder Servicing Agent of an
application in good order. Exchanges will continue to be made from a
shareholder's account in any MFS Fund, as long as the balance of the account is
sufficient to complete the exchange. Additional payments made to a shareholder's
account will extend the period that exchanges will continue to be made under the
Automatic Exchange Plan. However, if additional payments are added to an account
subject to the Automatic Exchange Plan shortly before an exchange is scheduled,
such funds may not be available for an exchange until the following month;
therefore, care should be used to avoid inadvertently terminating the Automatic
Exchange Plan through exhaustion of the account balance.
 
No transaction fee for exchanges will be charged in connection with the
Automatic Exchange Plan. However, exchanges of shares of MFS Money Market Fund,
MFS Government Money Market Fund and Class A shares of MFS Cash Reserve Fund
will be subject to any applicable sales charge. Changes in amounts to be
exchanged to each fund, the funds to which exchanges are to be made and the
timing of exchanges (monthly or quarterly), or termination of a shareholder's
participation in the Automatic Exchange Plan will be made after instructions in
writing or by telephone (an "Exchange Change Request") are received by the
Shareholder Servicing Agent in proper form (i.e., if in writing -- signed by the
record owner(s) exactly as shares are registered; if by telephone -- proper
account identification is given by the dealer or shareholder of record). Each
Exchange Change Request (other than termination of participation in the program)
must involve at least $50. Generally, if an Exchange Change Request is received
by telephone or in writing before the close of business on the last business day
of a month, the Exchange Change Request will be effective for the following
month's exchange.
 
A shareholder's right to make additional investments in any of the MFS Funds, to
make exchanges of shares from one MFS Fund to another and to withdraw from an
MFS Fund, as well as a shareholder's other rights and privileges are not
affected by a shareholder's participation in the Automatic Exchange Plan.
 
The Automatic Exchange Plan is part of the Exchange Privilege. For additional
information regarding the Automatic Exchange Plan, including the treatment of
any CDSC, see "Exchange Privilege" below.
 
  REINSTATEMENT PRIVILEGE: Shareholders of the Fund and shareholders of the
other MFS Funds (except MFS Money Market Fund, MFS Government Money Market Fund
and holders of Class A shares of MFS Cash Reserve Fund in the case where the
shares are acquired through direct purchase or reinvested dividends) who have
redeemed their shares have a one-time right to reinvest the redemption proceeds
in shares of any of the MFS Funds (if shares of the fund are available for sale)
at net asset value (without a sales charge) and, if applicable, with credit for
any CDSC paid. In the case of proceeds reinvested in shares of MFS Money Market
Fund, MFS Government Money Market Fund and Class A shares of MFS Cash Reserve
Fund, the shareholder has the right to exchange the acquired shares for shares
of another MFS Fund at net asset value pursuant to the exchange privilege
described below. Such a reinvestment must be made within 90 days of the
redemption and is limited to the amount of the redemption proceeds. If the
shares credited for any CDSC paid are then redeemed within six years of the
initial purchase in the case of Class B shares or 12 months of the initial
purchase in the case of certain Class A shares, a CDSC will be imposed upon
redemption. Although redemptions and repurchases of shares are taxable events, a
reinvestment within such 90-day period of time in the same fund may be
considered a "wash sale" and may result in the inability to recognize currently
all or a portion of any loss realized on the original redemption for federal
income tax purposes. Please see your tax adviser for further information.
 
EXCHANGE PRIVILEGE -- Subject to the requirements set forth below, some or all
of the shares in an account with the Fund for which payment has been received by
the Fund (i.e., an established account) may be exchanged for shares of the same
class of any of the other MFS Funds (if available for sale) at net asset value.
Exchanges will be made only after instructions in writing or by telephone (an
"Exchange Request") are received for an established account by the Shareholder
Servicing Agent.
 
                                       14
<PAGE>   108
 
Each Exchange Request must be in proper form (i.e., if in writing -- signed by
the record owner(s) exactly as the shares are registered; if by
telephone -- proper account identification is given by the dealer or shareholder
of record), and each exchange must involve either shares having an aggregate
value of at least $1,000 ($50 in the case of retirement plan participants whose
sponsoring organizations subscribe to the MFS FUNDamental 401(k) Plan or another
similar 401(k) record keeping system made available by the Shareholder Servicing
Agent) or all the shares in the account. Each exchange involves the redemption
of the shares of the Fund to be exchanged and the purchase at net asset value
(i.e., without a sales charge) of shares of the same class of the other MFS
Fund. Any gain or loss on the redemption of the shares exchanged is reportable
on the shareholder's federal income tax return. No more than five exchanges may
be made in any one Exchange Request by telephone. If an Exchange Request is
received by the Shareholder Servicing Agent prior to the close of regular
trading on the New York Stock Exchange (the "Exchange"), the exchange usually
will occur on that day if all of the requirements set forth above have been
complied with at that time. However, payment of the redemption proceeds by the
Fund, and thus the purchase of shares of the other MFS Fund, may be delayed for
up to seven days if the Fund determines that such a delay would be in the best
interest of all its shareholders. Investment dealers which have satisfied
criteria established by MFD may also communicate a shareholder's Exchange
Request to MFD by facsimile subject to the requirements set forth above.
 
No CDSC is imposed on exchanges among the MFS Funds, although liability for the
CDSC is carried forward to the exchanged shares. For purposes of calculating the
CDSC upon redemption of shares acquired in an exchange, the purchase of shares
acquired in one or more exchanges is deemed to have occurred at the time of the
original purchase of the exchanged shares.
 
Additional information with respect to any of the MFS Funds, including a copy of
its current prospectus, may be obtained from investment dealers or the
Shareholder Servicing Agent. A shareholder considering an exchange should obtain
and read the prospectus of the other MFS Fund and consider the differences in
objectives and policies before making any exchange. Shareholders of the other
MFS Funds (except holders of shares of MFS Money Market Fund, MFS Government
Money Market Fund and Class A shares of MFS Cash Reserve Fund acquired through
direct purchase or reinvested dividends prior to June 1, 1992) have the right to
exchange their shares for shares of the Fund, subject to the conditions, if any,
set forth in their respective prospectuses. In addition, unitholders of the MFS
Fixed Fund (a bank collective investment fund) have the right to exchange their
units (except units acquired through direct purchase) for shares of the Fund,
subject to the conditions, if any, imposed upon such unitholders by the MFS
Fixed Fund.
 
Any state income tax advantages for investment in shares of each state specific
series of MFS Municipal Series Trust may only benefit residents of such states.
Investors should consult with their own tax advisers to be sure this is an
appropriate investment, based on their residency and each state's income tax
laws.
 
The exchange privilege (or any aspect of it) may be changed or discontinued and
is subject to certain limitations, including certain restrictions on purchases
by market timers (see "Purchases" in the Prospectus).
 
6.   TAX STATUS
The Fund has elected to be treated and intends to qualify each year as a
"regulated investment company" under Subchapter M of the Internal Revenue Code
of 1986, as amended (the "Code"), by meeting all applicable requirements of
Subchapter M, including requirements as to the nature of the Fund's gross
income, the amount of Fund distributions (as a percentage of both the Fund's
overall income and its tax-exempt income), and the composition of the Fund's
portfolio assets. Because the Fund intends to distribute all of its net
investment income and net realized capital gains to shareholders in accordance
with the timing requirements imposed by the Code, it is not expected that the
Fund will be required to pay federal income or excise taxes. If the Fund should
fail to qualify as a "regulated investment company" in any year, the Fund would
incur a regular corporate federal income tax upon its taxable income and Fund
distributions would generally be taxable as ordinary dividend income to the
shareholders.
 
The portion of the Fund's distributions of net investment income that is
attributable to interest from tax-exempt securities will be designated by the
Fund as an "exempt-interest dividend" under the Code and will generally be
exempt from federal income tax in the hands of shareholders so long as at least
50% of the total value of the Fund's assets consists of tax-exempt securities at
the close of each quarter of the Fund's taxable year. Distributions of
tax-exempt interest earned from certain securities may, however, be treated as
an item of tax preference for shareholders under the federal alternative minimum
tax, and all exempt-interest dividends may increase a corporate shareholder's
alternative minimum tax. The percentage of income designated as tax-exempt will
be applied uniformly to all distributions by the Fund of net investment income
made during each fiscal year of the Fund and may differ from the percentage of
distributions consisting of tax-exempt interest in any particular month.
Shareholders are required to report exempt-interest dividends received from the
Fund on their federal income tax returns.
 
   
The Fund may also recognize some net investment income that is not tax-exempt,
as well as capital gains and losses as a result of the disposition of securities
and from certain options and futures transactions. Shareholders of the Fund
normally will have to pay federal income taxes, and any state or local income
taxes, on the non-exempt-interest dividends and capital gain distributions they
receive from the Fund; however, the Fund does not expect that the non-tax-exempt
portion of its net investment income, if any, will be substantial. That portion
of net investment income distributions not designated as exempt-interest
dividends and any distributions from net short-term capital gains are taxable to
shareholders as ordinary income for federal income tax purposes whether the
distributions are paid
    
 
                                       15
<PAGE>   109
 
   
in cash or reinvested in additional shares. Because the Fund expects to earn
primarily tax-exempt interest income, it is expected that no Fund dividends will
qualify for the dividends received deduction for corporations. Distributions of
net capital gains (i.e., the excess of net long-term capital gains over net
short-term capital losses), whether paid in cash or reinvested in additional
shares, are taxable to shareholders as long-term capital gains for federal
income tax purposes without regard to the length of time the shareholders have
held their shares. Any Fund dividend that is declared in October, November, or
December of any calendar year, that is payable to shareholders of record in such
a month, and that is paid the following January will be treated as if received
by the shareholders on December 31 of the year in which the dividend is
declared. The Fund will notify shareholders regarding the federal tax status of
its distributions after the end of each calendar year.
    
 
Any fund distribution of net capital gains or net short-term capital gains will
have the effect of reducing the per-share net asset value of shares in the Fund
by the amount of the distribution. Shareholders purchasing shares shortly before
the record date of any such distribution may thus pay the full price for the
shares and then effectively receive a portion of the purchase price back as a
taxable distribution.
 
Interest on indebtedness incurred by shareholders to purchase or carry shares of
the Fund will not be deductible for federal income tax purposes. Exempt-interest
dividends are taken into account in calculating the amount of social security
and railroad retirement benefits that may be subject to federal income tax.
Entities or persons who are "substantial users" (or persons related to
"substantial users") of facilities financed by private activity bonds should
consult their tax advisers before purchasing shares of the Fund.
 
   
In general, any gain or loss realized upon a taxable disposition of shares of
the Fund by a shareholder that holds such shares as a capital asset will be
treated as long-term capital gain or loss if the shares have been held for more
than twelve months and otherwise as a short-term capital gain or loss. However,
any loss realized upon a disposition of shares in the Fund held for six months
or less will be disallowed to the extent of any exempt-interest dividends
received with respect to those shares. If not disallowed, any such loss will be
treated as a long-term capital loss to the extent of any distributions of net
capital gain made with respect to those shares. Any loss realized upon a
disposition of shares may also be disallowed under rules relating to wash sales.
Gain may be increased (or loss reduced) upon a redemption of Class A shares of
the Fund within ninety days after their purchase followed by any purchase
(including purchases by exchange or by reinvestment) without payment of an
additional sales charge of Class A shares of the Fund or of another MFS Fund (or
any other shares of an MFS Fund generally sold subject to a sales charge).
    
 
   
The Fund's current dividend and accounting policies will affect the amount,
timing, and character of distributions to shareholders, and may, under certain
circumstances, make an economic return of capital taxable to shareholders. Any
investment in zero coupon bonds and certain securities purchased at a market
discount will cause the Fund to recognize income prior to the receipt of cash
payments with respect to those securities. In order to distribute this income
and avoid a tax on the Fund, the Fund may be required to liquidate portfolio
securities that it might otherwise have continued to hold, potentially resulting
in additional taxable gain or loss to the Fund.
    
 
The Fund's transactions in options and Futures Contracts will be subject to
special tax rules that may affect the amount, timing, and character of Fund
income and distributions to shareholders. For example, certain positions held by
the Fund on the last business day of each taxable year will be marked to market
(i.e., treated as if closed out) on that day, and any gain or loss associated
with the positions will be treated as 60% long-term and 40% short-term capital
gain or loss. Certain positions held by the Fund that substantially diminish its
risk of loss with respect to other positions in its portfolio may constitute
"straddles," and may be subject to special tax rules that would cause deferral
of Fund losses, adjustments in the holding periods of Fund securities, and
conversion of short-term into long-term capital losses. Certain tax elections
exist for straddles that may alter the effects of these rules. The Fund will
limit its activities in options and Futures Contracts to the extent necessary to
meet the requirements of Subchapter M of the Code.
 
Dividends and certain other payments to persons who are not citizens or
residents of the United States or U.S. entities ("Non-U.S. Persons") are
generally subject to U.S. federal income tax withholding at a rate of 30%. The
Fund intends to withhold U.S. federal income tax at the rate of 30% (or any
lower rate permitted under an applicable treaty) on taxable dividends and other
payments to Non-U.S. Persons that are subject to such withholding. Any amounts
overwithheld may be recovered by such persons by filing a claim for refund with
the U.S. Internal Revenue Service within the time period applicable to such
claims. Distributions received by the Fund by Non-U.S. Persons also may be
subject to tax under the laws of their own jurisdictions. The Fund is also
required in certain circumstances to apply backup withholding at the rate of 31%
on taxable dividends and redemption proceeds paid to any shareholder (including
a Non-U.S. Person) who does not furnish to the Fund certain information and
certifications or who is otherwise subject to backup withholding. Backup
withholding will not, however, be applied to payments that have been subject to
30% withholding.
 
As long as it qualifies as a regulated investment company under the Code, the
Fund will not be required to pay Massachusetts income or excise taxes.
 
The exemption of exempt-interest dividends for federal income tax purposes does
not necessarily result in exemption under the income or other tax laws of any
state or local taxing authority. Some states do exempt from tax that portion of
the exempt-interest dividend which represents interest received by a regulated
investment company on its holdings of tax-exempt securities of that state and
its political subdivisions and instrumentalities. Therefore, the Fund will
report annually to its shareholders the percentage of interest income earned by
the Fund during the preceding year on Municipal Bonds and will
 
                                       16
<PAGE>   110
 
   
indicate, on a state-by-state basis only, the source of such income. Residents
of certain states may be subject to an intangibles tax or a personal property
tax on all or a portion of the value of their shares. Each shareholder is
advised to consult his own tax adviser regarding the exemption of
exempt-interest dividends under applicable state or local law, as well as
regarding the tax consequences of an investment in the fund.
    
 
7.   DETERMINATION OF NET ASSET VALUE AND PERFORMANCE
NET ASSET VALUE: The net asset value per share of each class of the Fund is
determined each day during which the Exchange is open for trading. (As of the
date of this SAI, the Exchange is open for trading every weekday except for the
following holidays or the days on which they are observed: New Year's Day,
Martin Luther King, Jr., Day, Presidents' Day, Good Friday, Memorial Day,
Independence Day, Labor Day, Thanksgiving Day and Christmas Day.) This
determination is made once during each such day as of the close of regular
trading on the Exchange by deducting the amount of the liabilities attributable
to the class from the value of the assets attributable to the class and dividing
the difference by the number of shares of the class outstanding. Debt securities
(other than short-term obligations), including listed issues, are valued on the
basis of valuations furnished by a pricing service which utilizes both
dealer-supplied valuations and electronic data processing techniques which take
into account appropriate factors such as institution-size trading in similar
groups of securities, yield, quality, coupon rate, maturity, type of issue,
trading characteristics and other market data, without exclusive reliance upon
exchange or over-the-counter prices, since such valuations are believed to
reflect more accurately the fair value of such securities. Use of the pricing
service has been approved by the Trust's Board of Trustees. Short-term
obligations with a remaining maturity in excess of 60 days will be valued based
upon dealer supplied valuations. Other short-term obligations are valued at
amortized cost, which constitutes fair value as determined by the Board of
Trustees. Positions in listed options, Futures Contracts and Options on Futures
Contracts will normally be valued at the settlement price on the exchange on
which they are primarily traded. Positions in over-the-counter options will be
valued using dealer supplied valuations. Portfolio securities for which there
are no such valuations are valued at fair value as determined in good faith by
or at the direction of the Board of Trustees.
 
PERFORMANCE INFORMATION
TOTAL RATE OF RETURN: The Fund will calculate its total rate of return for each
class of shares for certain periods by determining the average annual compounded
rates of return over those periods that would cause an investment of $1,000
(made with all dividends and distributions reinvested and reflecting the CDSC or
the maximum public offering price) to reach the value of that investment at the
end of the periods. The Fund may also calculate (i) a total rate of return,
which is not reduced by the CDSC (4% maximum for Class B shares) and therefore
may result in a higher rate of return, (ii) a total rate of return assuming an
initial account value of $1,000, which will result in a higher rate of return
since the value of the initial account will not be reduced by the maximum sales
charge (currently 4.75%) and/or (iii) total rates of return which represent
aggregate performance over a period or year-by-year performance, and which may
or may not reflect the effect of the maximum or other sales charge or CDSC.
 
The Fund offers multiple classes of shares which were initially offered for sale
to, and purchase by, the public on different dates. The calculation of total
rate of return for a class of shares which has a later class inception date than
another class of shares of the Fund is based both on (i) the performance of the
Fund's newer class from its inception date and (ii) the performance of the
Fund's oldest class from its inception date up to the date of the newer class.
 
As discussed in the Prospectus, the sales charges, expenses and expense ratios,
and therefore the performance, of the Fund's classes of shares differ. In
calculating total rate of return for a newer class of shares in accordance with
certain formulas required by the SEC, the performance will be adjusted to take
into account the fact that the newer class is subject to a different sales
charge than the oldest class (e.g., if the newer class is Class A shares, the
total rate of return quoted will reflect the deduction of the initial sales
charge applicable to Class A shares; if the newer class is Class B shares, the
total rate of return quoted will reflect the deduction of the CDSC applicable to
Class B shares). However, the performance will not be adjusted to take into
account the fact that the newer class of shares bears different class specific
expenses than the oldest class of shares (e.g., Rule 12b-1 fees). Therefore, the
total rate of return quoted for a newer class of shares will differ from the
return that would be quoted had the newer class of shares been outstanding for
the entire period over which the calculation is based (i.e., the total rate of
return quoted for the newer class will be higher than the return that would have
been quoted had the newer class of shares been outstanding for the entire period
over which the calculation is based if the class specific expenses for the newer
class are higher than the class specific expenses of the oldest class, and the
total rate of return quoted for the newer class will be lower than the return
that would be quoted had the newer class of shares been outstanding for this
entire period if the class specific expenses for the newer class are lower than
the class specific expenses of the oldest class).
 
   
Total rate of return quotations for each class are presented in Appendix A
attached hereto.
    
 
   
Any performance results, as well as any yield, tax-equivalent yield or total
rate of return quotation provided by the Fund, should not be considered as
representative of the performance of the Fund in the future since the net asset
value and public offering price of shares of the Fund will vary based not only
on the type, quality and maturities of the securities held in the Fund's
portfolio, but also on changes in the current value of such securities and on
changes in the expenses of the Fund. These factors and possible differences in
the methods used to calculate yields, tax-equivalent yields and total rates of
return should be considered when comparing the yield, tax-equivalent
    
 
                                       17
<PAGE>   111
 
yield and total rate of return of the Fund to yields, tax-equivalent yields and
total rates of return published for other investment companies or other
investment vehicles. Total rate of return reflects the performance of both
principal and income. Current net asset value as well as account balance
information may be obtained by calling 1-800-MFS-TALK (637-8255).
 
   
YIELD: Any yield quotation for a class of shares of the Fund is based on the
annualized net investment income per share allocated to such class of the Fund
over a 30-day period. The yield for a class of shares of the Fund is calculated
by dividing the net investment income per share of the Fund allocated to such
class earned during the period by the maximum offering price per share of such
class of the Fund on the last day of that period. The resulting figure is then
annualized. Net investment income per share of a class is determined by dividing
(i) the dividends and interest earned by the Fund and allocated to such class
during the period, minus accrued expenses of such class for the period, by (ii)
the average number of Fund shares of such class entitled to receive dividends
during the period multiplied by the maximum offering price per share of such
Class on the last day of the period for Class A shares. The Fund's yield
calculations assume a maximum sales charge of 4.75%. The yield calculations
assume no CDSC is paid. Yield quotations for each class of shares are presented
in Appendix A attached hereto.
    
 
   
TAX-EQUIVALENT YIELD: The Fund's tax-equivalent yield is calculated by
determining the rate of return that would have to be achieved on a fully taxable
investment to produce the after-tax equivalent of the Fund's yield. In
calculating tax-equivalent yield, the Fund assumes certain tax brackets for
shareholders. Tax equivalent yield quotations for each class of shares are
presented in Appendix A attached hereto.
    
 
   
CURRENT DISTRIBUTION RATE: Yield, which is calculated according to a formula
prescribed by the Securities and Exchange Commission, is not indicative of the
amounts which were or will be paid to the Fund's shareholders. Amounts paid or
expected to be paid to shareholders of each class are reflected in the quoted
"current distribution rate" for that class. The current distribution rate for a
class is computed by (i) annualizing the distributions (excluding short-term
capital gains) of the class for a stated period; (ii) adding any short-term
capital gains paid within the immediately preceding twelve-month period; and
(iii) dividing the result by the maximum offering price or net asset value per
share on the last day of the period. The current distribution rate differs from
the yield computation because it may include distributions to shareholders from
sources other than dividends and interest, such as premium income for option
writing, short-term capital gains and return of invested capital, and may be
calculated over a different period of time. Current distribution rate quotations
for each class of shares are presented in Appendix A attached hereto.
    
 
From time to time the Fund may, as appropriate, quote Fund rankings or reprint
all or a portion of evaluations of fund performance and operations appearing in
various independent publications, including but not limited to the following:
Money, Fortune, U.S. News and World Report, Kiplinger's Personal Finance, The
Wall Street Journal, Barron's, Investors Business Daily, Newsweek, Financial
World, Financial Planning, Investment Advisor, USA Today, Pensions and
Investments, SmartMoney, Forbes, Global Finance, Registered Representative,
Institutional Investor, the Investment Company Institute, Johnson's Charts,
Morningstar, Lipper Analytical Services, Inc., CDA Wiesenberger, Shearson Lehman
and Salomon Bros. Indices, Ibbotson, Business Week, Lowry Associates, Media
General, Investment Company Data, The New York Times, Your Money, Strangers
Investment Advisor, Financial Planning on Wall Street, Standard and Poor's,
Individual Investor, The 100 Best Mutual Funds You Can Buy, by Gordon K.
Williamson, Consumer Price Index, and Sanford C. Bernstein & Co. Fund
performance may also be compared to the performance of other mutual funds
tracked by financial or business publications or periodicals.
 
The Fund may also quote evaluations mentioned in independent radio or television
broadcasts.
 
From time to time the Fund may use charts and graphs to illustrate the past
performance of various indices such as those mentioned above and illustrations
using hypothetical rates of return to illustrate the effects of compounding and
tax-deferral.
 
   
The Fund may also use charts, graphs or other presentation formats to illustrate
the historical correlation of its performance to fund categories established by
Morningstar (or other nationally recognized statistical ratings organizations)
and to other MFS Funds.
    
 
From time to time, the Fund may discuss or quote its current portfolio manager
as well as other investment personnel, including such persons' views on: the
economy; securities markets; portfolio securities and their issuers; investment
philosophies, strategies, techniques and criteria used in the selection of
securities to be purchased or sold for the Fund; the Fund's portfolio holdings;
the investment research and analysis process; the formulation and evaluation of
investment recommendations; and the assessment and evaluation of credit,
interest rate, market and economic risks, and similar or related matters.
 
From time to time the Fund may also discuss or quote the views of its
distributor, its investment adviser and other financial planning, legal, tax,
accounting, insurance, estate planning and other professionals, or from surveys,
regarding individual and family financial planning. Such views may include
information regarding: retirement planning; tax management strategies; estate
planning; general investment techniques (e.g., asset allocation and disciplined
saving and investing); business succession; ideas and information provided
through the MFS Heritage Planning(sm) program, an intergenerational financial
planning assistance program; issues with respect to insurance (e.g., disability
and life insurance and Medicare supplemental insurance); issues regarding
financial and health care management for elderly family members; and other
similar or related matters.
 
The Fund may advertise examples of the effects of periodic investment plans,
including the principle of dollar cost averaging. In such a program, an investor
invests a fixed dollar amount in a fund at periodic intervals, thereby
purchasing fewer shares
 
                                       18
<PAGE>   112
 
when prices are high and more shares when prices are low. While such a strategy
does not assure a profit or guard against a loss in a declining market, the
investor's average cost per share can be lower than if fixed numbers of shares
are purchased at the same intervals.
 
   
From time to time, the Fund may also advertise annual returns showing the
cumulative value of an initial investment in the Fund in various amounts over
specified periods, with capital gain and dividend distributions invested in
additional shares or taken in cash, and with no adjustment for any income taxes
(if applicable) payable by shareholders.
    
 
MFS FIRSTS: MFS has a long history of innovations.
 
  --  1924 -- Massachusetts Investors Trust is established as the first mutual
       fund in America.
 
  --  1924 -- Massachusetts Investors Trust is the first mutual fund to make
       full public disclosure of its operations in shareholder reports.
 
  --  1932 -- One of the first internal research departments is established to
       provide in-house analytical capability for an investment management firm.
 
  --  1933 -- Massachusetts Investors Trust is the first mutual fund to register
       under the Securities Act of 1933 ("Truth in Securities Act" or "Full
       Disclosure Act").
 
  --  1936 -- Massachusetts Investors Trust is the first mutual fund to let
       shareholders take capital gain distributions either in additional shares
       or in cash.
   
 
  --  1976 -- MFS(R) Municipal Bond Fund is among the first municipal bond funds
       established.
    
 
  --  1979 -- Spectrum becomes the first combination fixed/ variable annuity
       with no initial sales charge.
 
   
  --  1981 -- MFS(R) Global Governments Fund is established as America's first
       globally diversified fixed-income mutual fund.
    
   
 
  --  1984 -- MFS(R) Municipal High Income Fund is the first mutual fund to seek
       high tax-free income from lower-rated municipal securities.
    
   
 
  --  1986 -- MFS(R) Managed Sectors Fund becomes the first mutual fund to
       target and shift investments among industry sectors for shareholders.
    
   
 
  --  1986 -- MFS(R) Municipal Income Trust is the first closed-end, high-yield
       municipal bond fund traded on the New York Stock Exchange.
    
   
 
  --  1987 -- MFS(R) Multimarket Income Trust is the first closed-end,
       multimarket high income fund listed on the New York Stock Exchange.
    
   
 
  --  1989 -- MFS(R) Regatta becomes America's first non-qualified market-value
       adjusted fixed/variable annuity.
    
 
   
  --  1990 -- MFS(R) Global Total Return Fund is the first global balanced fund.
    
 
   
  --  1993 -- MFS(R) Global Growth Fund is the first global emerging markets
       fund to offer the expertise of two sub-advisers.
    
 
   
  --  1993 -- MFS(R) becomes money manager of MFS(R) Union Standard(R) Equity
       Fund, the first Fund to invest in companies deemed to be union-friendly
       by an Advisory Board of senior labor officials, senior managers of
       companies with significant labor contracts, academics and other national
       labor leaders or experts.
    
 
8.   DISTRIBUTION PLAN
 
The Trustees have adopted a Distribution Plan for Class B shares (the
"Distribution Plan") pursuant to Section 12(b) of the 1940 Act and Rule 12b-1
thereunder (the "Rule") after having concluded that there is a reasonable
likelihood that the Distribution Plan would benefit the Fund and its
shareholders. The Distribution Plan is designed to promote sales, thereby
increasing the net assets of the Fund attributable to Class B shares. Such an
increase may reduce the Fund's Class B expense ratio to the extent that the
Fund's fixed costs are spread over a larger net asset base. Also, an increase in
net assets may lessen the adverse effect that could result were the Fund
required to liquidate portfolio securities to meet redemptions. There is,
however, no assurance that the net assets of the Fund will increase or that the
other benefits referred to above will be realized.
 
The Distribution Plan is described in the Prospectus under the caption
"Distribution Plan," which is incorporated herein by reference. The following
information supplements this Prospectus discussion.
 
SERVICE FEES: Except in the case of the first year service fee, no service fees
will be paid to any securities dealer who is the holder or dealer of record for
investors who own Class B shares having an aggregate net asset value of less
than $750,000 or such other amount as may be determined by MFD from time to
time. MFD, however, may waive this minimum amount requirement from time to time.
Dealers may from time to time be required to meet certain other criteria in
order to receive service fees.
 
MFD or its affiliates shall be entitled to receive any service fee payable under
the Distribution Plan for which there is no dealer of record or for which
qualification standards have not been met as partial consideration for personal
services and/or account maintenance services performed by MFD or its affiliates
for shareholder accounts.
 
DISTRIBUTION FEES: The purpose of distribution payments to MFD under the
Distribution Plan is to compensate MFD for its distribution services to the
Fund. MFD pays commissions to dealers as well as expenses of printing
prospectuses and reports used for sales purposes, expenses with respect to the
preparation and printing of sales literature and other distribution related
expenses, including, without limitation, the cost necessary to provide
distribution-related services, or personnel, travel, office expenses and
equipment.
 
                                       19
<PAGE>   113
 
   
DISTRIBUTION AND SERVICE FEES PAID DURING THE FUND'S LAST FISCAL YEAR: During
fiscal year ended August 31, 1998, the Fund paid the following Distribution Plan
expenses:
    
 
   
<TABLE>
<CAPTION>
                           AMOUNT OF       AMOUNT OF       AMOUNT OF
                          DISTRIBUTION   DISTRIBUTION    DISTRIBUTION
                          AND SERVICE     AND SERVICE     AND SERVICE
                          FEES PAID BY   FEES RETAINED   FEES RECEIVED
    CLASS OF SHARES           FUND          BY MFD        BY DEALERS
    ---------------       ------------   -------------   -------------
<S>                       <C>            <C>             <C>
Class B Shares..........    $615,624       $582,298        $ 33,326
</TABLE>
    
 
   
GENERAL: The Distribution Plan will remain in effect until August 1, 1999, and
will continue in effect thereafter only if such continuance is specifically
approved at least annually by vote of both the Trustees and a majority of the
Trustees who are not "interested persons" or financially interested parties of
the Plan ("Distribution Plan Qualified Trustees"). The Distribution Plan also
requires that the Fund and MFD each shall provide the Trustees, and the Trustees
shall review, at least quarterly, a written report of the amounts expended (and
purposes therefor) under the Plan. The Distribution Plan may be terminated at
any time by vote of a majority of the Distribution Plan Qualified Trustees or by
vote of the holders of a majority of the Class B shares of the Fund (as defined
in "Investment Restrictions"). All agreements relating to the Distribution Plan
entered into between the Fund or MFD and other organizations must be approved by
the Board of Trustees, including a majority of the Distribution Plan Qualified
Trustees. Agreements under the Distribution Plan must be in writing, will be
terminated automatically if assigned, and may be terminated at any time without
payment of any penalty, by vote of a majority of the Distribution Plan Qualified
Trustees or by vote of the holders of a majority of the Class B shares of the
Fund. The Distribution Plan may not be amended to increase materially the amount
of permitted distribution expenses without the approval of a majority of the
Class B shares of the Fund (as defined in "Investment Restrictions") or may be
materially amended in any case without a vote of the Trustees and a majority of
the Distribution Plan Qualified Trustees. The selection and nomination of
Distribution Plan Qualified Trustees shall be committed to the discretion of the
non-interested Trustees then in office. No Trustee who is not an "interested
person" has any financial interest in any of the Distribution Plan or in any
related agreement.
    
 
9.   DESCRIPTION OF SHARES, VOTING RIGHTS AND LIABILITIES
 
The Trust's Declaration of Trust permits the Trustees to issue an unlimited
number of full and fractional Shares of Beneficial Interest (without par value)
of one or more series and to divide or combine the shares of any series into a
greater or lesser number of shares without thereby changing the proportionate
beneficial interests in that series. The Trustees have currently authorized
shares of the Fund and three other series. The Declaration of Trust further
authorizes the Trustees to classify or reclassify any series of shares into one
or more classes. Pursuant thereto, the Trustees have authorized the issuance of
two classes of shares for this series of the Trust, Class A shares and Class B
shares, one class of shares for each of the Trust's two money market series, and
Class A, Class B, Class C and Class I shares of one other of the Trust's four
series. Each share of a class of the Fund represents an equal proportionate
interest in the assets of the Fund allocable to that class. The Trust reserves
the right to create and issue additional series or classes of shares, in which
case the shares of each class of a series would participate equally in the
earnings, dividends and assets allocable to that class of the particular series
(subject to any expenses attributable to that class. Upon liquidation of the
Fund, shareholders of each class of the Fund are entitled to share pro rata in
the Fund's net assets allocable to such class available for distribution to
shareholders.
 
Shareholders are entitled to one vote for each share held and may vote in the
election of Trustees and on other matters submitted to meetings of shareholders.
Although Trustees are not elected annually by the shareholders, shareholders
have under certain circumstances the right to remove one or more Trustees in
accordance with the provisions of section 16(c) of the 1940 Act. No material
amendment may be made to the Trust's Declaration of Trust without the
affirmative vote of a majority of its shares (as defined in "Investment
Restrictions") or without a meeting by an instrument in writing, signed by a
majority of the Trustees and consented to by the holders of not less than a
majority of the shares outstanding and entitled to vote. Shares have no
preemptive or conversion rights (except as described in the Prospectus under
"Purchases -- Conversion of Class B Shares"). Shares are fully paid and
nonassessable. The Trust may enter into a merger or consolidation, or sell all
or substantially all of its assets (or all or substantially all of the assets
belonging to any series of the Trust), if approved by the vote of the holders of
two-thirds of the Trust's outstanding shares voting as a single class, or of the
affected series of the Trust, as the case may be, except that if the Trustees of
the Trust recommend such merger, consolidation or sale, the approval by vote of
the holders of a majority of the Trust's or the affected series' outstanding
shares (as defined in "Investment Restrictions") will be sufficient. The Trust
or any series of the Trust may also be terminated (i) upon liquidation and
distribution of its assets, if approved by the vote of the holders of two-
thirds of its outstanding shares, or (ii) by the Trustees by written notice to
the shareholders of the Trust or the affected series. If not so terminated the
Trust will continue indefinitely.
 
The Trust is an entity of the type commonly known as a "Massachusetts business
trust". Under Massachusetts law, shareholders of such a trust may, under certain
circumstances, be held personally liable as partners for its obligations.
However, the Declaration of Trust contains an express disclaimer of shareholder
liability for acts or obligations of the Trust and provides for indemnification
and reimbursement of expenses out of the Trust property for any shareholder held
personally liable for the obligations of the Trust. The Declaration of Trust
also provides that the Trust shall maintain appropriate insurance (for example,
fidelity bonding and errors and omissions insurance) for the protection of the
Trust, its shareholders, Trustees, officers, employees and agents covering
possible tort and other liabilities. Thus, the risk of a shareholder incurring
financial loss
 
                                       20
<PAGE>   114
 
on account of shareholder liability is limited to circumstances in which both
inadequate insurance existed and the Trust itself was unable to meet its
obligations.
 
The Declaration of Trust further provides that obligations of the Trust are not
binding upon the Trustees individually but only upon the property of the Trust
and that the Trustees will not be liable for any action or failure to act, but
nothing in the Declaration of Trust protects a Trustee against any liability to
which he would otherwise be subject by reason of willful misfeasance, bad faith,
gross negligence, or reckless disregard of the duties involved in the conduct of
his office.
 
10. INDEPENDENT AUDITORS AND FINANCIAL STATEMENTS
 
Deloitte & Touche LLP, are the Fund's independent auditors providing audit
services, tax return preparation and assistance and consultation with respect to
the preparation of filings with the SEC.
 
   
The Portfolio of Investments at August 31, 1998, the Statement of Assets and
Liabilities at August 31, 1998, the Statement of Operations for the year ended
August 31, 1998, the Statements of Changes in Net Assets for the years ended
August 31, 1998, and 1997, the Notes to Financial Statements and the Independent
Auditors' Report, each of which is included in the Annual Report to shareholders
of the Fund, are incorporated by reference into this SAI and have been so
incorporated in reliance upon the report of Deloitte & Touche LLP, independent
auditors, as experts in accounting and auditing. A copy of the Annual Report
accompanies this SAI.
    
 
                                       21
<PAGE>   115
 
                                                                      APPENDIX A
 
   
                            PERFORMANCE INFORMATION
    
 
   
The performance quotations below should not be considered as representative of
the performance of the Fund in the future since the net asset value and public
offering price of shares of the Fund will vary. See "Performance Information" in
the SAI.
    
 
   
All performance quotations are as of August 31, 1998.
    
 
   
<TABLE>
<CAPTION>
                                                                                             TAX EQUIVALENT
                                                                                              30-DAY YIELD
                                                                                             TAX BRACKETS:       CURRENT
                                                                                             --------------    DISTRIBUTION
                                             1 YEAR    5 YEAR     10 YEAR    30-DAY YIELD     28%      31%       RATE(2)
                                             ------    ------     -------    ------------     ---      ---     ------------
<S>                                          <C>       <C>        <C>        <C>             <C>      <C>      <C>
Class A with sales charge..................   2.66%     4.24%      7.42%         4.43%       6.18%    6.45%        4.90%
Class A without sales charge...............   7.78%     5.26%      7.95%
Class B with CDSC..........................   2.85%     3.92%(1)   7.44%(1)                                        4.15%
Class B without CDSC.......................   6.85%     4.27%(1)   7.44%(1)      3.90%       5.41%    5.65%
</TABLE>
    
 
- ---------------
 
(1) Class B share performance includes the performance of the Fund's Class A
    shares for periods prior to the inception of Class B shares on September 7,
    1993. Sales charges, expenses and expense ratios, and therefore performance,
    for Class A and Class B shares differ. Class B share performance has been
    adjusted to reflect that Class B shares generally are subject to a CDSC
    (unless the performance quotation does not give effect to the CDSC) whereas
    Class A shares generally are subject to an initial sales charge. Class B
    share performance has not, however, been adjusted to reflect differences in
    operating expenses (e.g., Rule 12b-1 fees), which generally are lower for
    Class A shares.
 
   
(2) Annualized based on last distribution.
    
 
                                       A-1
<PAGE>   116
 
INVESTMENT ADVISER
Massachusetts Financial Services Company
500 Boylston Street, Boston, MA 02116
617-954-5000
DISTRIBUTOR
MFS Fund Distributors, Inc.
500 Boylston Street, Boston, MA 02116
(617)954-5000
CUSTODIAN AND DIVIDEND DISBURSING AGENT
State Street Bank and Trust Company
225 Franklin Street, Boston, MA 02110
SHAREHOLDER SERVICING AGENT
MFS Service Center, Inc.
500 Boylston Street, Boston, MA 02116
Toll free: (800)-225-2606
Mailing Address:
P.O. Box 2281, Boston, MA 02107-9906
INDEPENDENT AUDITORS
Deloitte & Touche LLP
125 Summer Street, Boston, MA 02110
MFS(R)
MUNICIPAL
BOND FUND
 
500 BOYLSTON STREET
BOSTON, MA 02116
 
[MFS Logo]
<PAGE>   117
                            MFS MID CAP GROWTH FUND

   
     Supplement to the MFS Mid Cap Growth Fund Prospectus and Statement of 
Additional Information dated January 1, 1999.
    

   
     The following information should be read in conjunction with the Fund's 
Prospectus and Statement of Additional Information ("SAI"), also dated January 
1, 1999, and contains a description of Class I shares.
    

     Class I shares are available for purchase only by certain investors as 
described under the caption "Eligible Purchasers" below.

   
EXPENSE SUMMARY
<TABLE>
<CAPTION>
                                                                                Class I
                                                                                -------
<S>                                                                             <C>
Shareholder Transaction Expenses:
  Maximum Initial Sales Charge Imposed on Purchases of Fund
    Shares (as a percentage of offering price)...................................  None
  Maximum Contingent Deferred Sales Charge (as a percentage
    of original purchase price or redemption proceeds, as applicable)............  None

Annual Operating Expenses of the Fund (as a percentage of average net assets):
  Management Fees................................................................  0.75%
  Rule 12b-1 Fees................................................................  None
  Other Expenses(1)..............................................................  0.43%
  Total Operating Expenses.......................................................  1.18%
</TABLE>
    
- -------------- 
(1) The Fund has an expense offset arrangement which reduces the Fund's
    custodian fee based upon the amount of cash maintained by the Fund with its
    custodian and dividend disbursing agent, and may enter into other such
    arrangements and directed brokerage arrangements (which would also have the
    effect of reducing the Fund's expenses). Any such fee reductions are not
    reflected under "Other Expenses."

                              Example of Expenses
                              -------------------

     An investor would pay the following dollar amounts of expenses on a $1,000 
investment in Class I shares of the Fund, assuming (a) a 5% annual return and 
(b) redemption at the end of each of the time periods indicated:

   
<TABLE>
<CAPTION>
               Period                                   Class I
               ------                                   -------
               <S>                                      <C>
               1 year.................................   $ 12
               3 years................................     37
               5 years................................     65
               10 years...............................    143
</TABLE>
    

     The purpose of the expense table above is to assist investors in 
understanding the various costs and expenses that a shareholder of the Fund 
will bear directly or indirectly. A more complete description of the Fund's 
management fee is set forth under the caption "Management of the Fund" in the 
Prospectus.

     The "Example" set forth above should not be considered a representation of 
past or future expenses of the Fund; actual expenses may be greater or less 
than those shown.

CONDENSED FINANCIAL INFORMATION

     The following information should be read in conjunction with the financial 
statements included in the Fund's Annual Report to shareholders, which are 
incorporated by reference into the SAI.


                                      -1-

<PAGE>   118
FINANCIAL HIGHLIGHTS - CLASS I SHARES

   
<TABLE>
<CAPTION>
                                                       Year Ended     Period Ended
                                                    August 31, 1998  August 31, 1997*
                                                    ---------------  ----------------
<S>                                                    <C>               <C>
                                                       Class I
Per share data (for a share outstanding throughout
  each period):  
Net asset value - beginning of period                  $  9.44            $ 8.50
Income from investment operations#-
     Net investment loss                               $ (0.08)           $(0.05)
     Net realized and unrealized gain (loss) on
       investments and foreign currency transactions     (1.32)             0.99
         Total from investment operations              $ (1.40)           $ 0.94
Less distributions declared to shareholders from net
     realized gain on investments and foreign
     currency transactions                             $ (0.31)           $  --
Net asset value - end of period                        $  7.73            $ 9.44
Total return                                            (15.23)%           11.06%++
Ratios (to average net assets)/Supplemental data:
     Expenses##                                           1.18%             1.03%+
     Net investment loss                                 (0.82)%           (0.74)%+
Portfolio turnover                                         168%              170%
Net assets at end of period (000 omitted)                 $925            $1,384   
</TABLE>
    
- --------------------
   
*   For the period from the inception of Class I shares, January 2, 1997, 
    through August 31, 1997.
    
   
+   Annualized
    
   
++  Not Annualized
    
#   Per share distributions are based on average shares outstanding.

##  The Fund's expenses are calculated without reduction for fees paid 
    indirectly.

ELIGIBLE PURCHASERS

Class I shares are available for purchase only by the following Eligible 
Purchasers:

(i)   certain retirement plans established for the benefit of employees of
      Massachusetts Financial Services Company ("MFS"), the Fund's investment
      adviser, and employees of MFS' affiliates;

(ii)  any fund distributed by MFS Fund Distributors, Inc. ("MFD"), the Fund's
      distributor, if the fund seeks to achieve its investment objective by
      investing primarily in shares of the Fund and other funds distributed by
      MFD;

(iii) any retirement plan, endowment or foundation which (a) purchases shares
      directly through MFD (rather than through a third party broker or dealer
      or other financial intermediary); (b) has, at the time of purchase of
      Class I shares, aggregate assets of at least $100 million; and (c)
      invests at least $10 million in Class I shares of the Fund either alone or
      in combination with investments in Class I shares of other MFS funds
      distributed by MFD (additional investments may be made in any amount);
      provided that MFD may accept purchases from smaller plans, endowments or
      foundations or in smaller amounts if it believes, in its sole discretion,
      that such entity's aggregate assets will equal or exceed $100 million, or
      that such entity will make additional investments which will cause its
      total investment to equal or exceed $10 million, within a reasonable
      period of time;

   
(iv)  bank trust departments or law firms acting as trustee or manager for trust
      accounts which initially invest, on behalf of their trust clients, at
      least $100,000 in Class I shares of the Fund (additional investments may
      be made in any amount); provided that MFD may accept smaller initial
      purchases if it believes, in its sole discretion, that the bank trust
      department or law firm will make additional investments, on behalf of its
      trust clients, which will cause its total investment to equal or exceed
      $100,000 within a reasonable period of time; and 
    

(v)   certain retirement plans offered, administered or sponsored by insurance
      companies, provided that these plans and insurance companies meet certain
      criteria established by MFD from time to time.

                                      -2-

 



<PAGE>   119
     In no event will the Fund, MFS, MFD or any of their affiliates pay any 
sales commissions or compensation to any third party in connection with the 
sale of Class I shares; the payment of any such sales commission or 
compensation would, under the Fund's policies, disqualify the purchaser as an 
eligible investor of Class I shares.

SHARE CLASSES OFFERED BY THE FUND

     Four classes of shares of the Fund currently are offered for sale, Class A 
shares, Class B shares, Class C shares and Class I shares. Class I shares are 
available for purchase only by Eligible Purchasers, as defined above, and are 
described in this Supplement. Class A shares, Class B shares and Class C shares 
are described in the Fund's Prospectus and are available for purchase by the 
general public.

     Class A shares are offered at net asset value plus an initial sales charge 
up to a maximum of 5.75% of the offering price (or a contingent deferred sales 
charge (a "CDSC") upon redemption of 1.00% during the first year in the case of 
purchases of $1 million or more and certain purchases by retirement plans), and 
are subject to an annual distribution fee and service fee up to a maximum of 
0.35% per annum. Class B shares are offered at net asset value without an 
initial sales charge but are subject to a CDSC upon redemption (declining from 
4.00% during the first year to 0% after six years) and an annual distribution 
fee and service fee up to a maximum of 1.00% per annum; Class B shares convert 
to Class A shares approximately eight years after purchase. Class C shares are 
offered at net asset value without an initial sales charge but are subject to a 
CDSC upon redemption of 1.00% during the first year and an annual distribution 
fee and service fee up to a maximum of 1.00% per annum. Class I shares are 
offered at net asset value without an initial sales charge or CDSC and are not 
subject to a distribution or service fee. Class C and Class I shares do not 
convert to any other class of shares of the Fund.

OTHER INFORMATION

     Eligible Purchasers may purchase Class I shares only directly through MFD. 
Eligible Purchasers may exchange Class I shares of the Fund for Class I shares 
of any other MFS Fund available for purchase by such Eligible Purchasers at 
their net asset value (if available for sale), and may exchange Class I shares 
of the Fund for shares of the MFS Money Market Fund (if available for sale), 
and may redeem Class I shares of the Fund at net asset value. Distributions 
paid by the Fund with respect to Class I shares generally will be greater than 
those paid with respect to Class A shares, Class B shares and Class C shares 
because expenses attributable to Class A shares, Class B shares and Class C 
shares generally will be higher.


   
                The date of this Supplement is January 1, 1999.
    


                                      -3-
<PAGE>   120
 
   
<TABLE>
<S>                                   <C>
    
   
                                                                   PROSPECTUS
                                                              JANUARY 1, 1999
MFS(R) MID CAP GROWTH FUND              CLASS A SHARES OF BENEFICIAL INTEREST
(A member of the MFS Family of          CLASS B SHARES OF BENEFICIAL INTEREST
Funds(R))                               CLASS C SHARES OF BENEFICIAL INTEREST
</TABLE>
    
 
- --------------------------------------------------------------------------------
500 Boylston Street, Boston, Massachusetts 02116      (617) 954-5000
 
   
This Prospectus pertains to the MFS Mid Cap Growth Fund (the "Fund"), a
non-diversified series of MFS Series Trust IV (the "Trust"), an open-end
investment company presently consisting of four series. The investment objective
of the Fund is to seek to obtain long-term growth of capital. The Fund seeks to
achieve this objective by investing at least 65% of its assets, under normal
market conditions, in equity securities of companies with medium market
capitalization which the Adviser believes have above-average growth potential.
THE FUND IS INTENDED FOR INVESTORS WHO UNDERSTAND AND ARE WILLING TO ACCEPT THE
RISKS ENTAILED IN SEEKING LONG-TERM GROWTH OF CAPITAL. See "Additional Risk
Factors." The minimum initial investment generally is $1,000 per account (see
"Information Concerning Shares of the Fund -- Purchases").
    
 
The Fund's investment adviser and distributor are Massachusetts Financial
Services Company ("MFS" or the "Adviser") and MFS Fund Distributors, Inc.
("MFD"), respectively, both of which are located at 500 Boylston Street, Boston,
Massachusetts 02116.
 
                                                        (continued on next page)
 
INVESTMENT PRODUCTS ARE NOT INSURED BY THE FDIC OR ANY OTHER GOVERNMENT AGENCY,
AND ARE NOT DEPOSITS OR OTHER OBLIGATIONS OF, OR GUARANTEED BY, ANY FINANCIAL
INSTITUTION. SHARES OF MUTUAL FUNDS ARE SUBJECT TO INVESTMENT RISK, INCLUDING
POSSIBLE LOSS OF THE PRINCIPAL AMOUNT INVESTED, AND WILL FLUCTUATE IN VALUE. YOU
MAY RECEIVE MORE OR LESS THAN YOU PAID WHEN YOU REDEEM YOUR SHARES.
  THESE SECURITIES HAVE NOT BEEN APPROVED OR DISAPPROVED BY THE SECURITIES AND
 EXCHANGE COMMISSION OR ANY STATE SECURITIES COMMISSION NOR HAS THE SECURITIES
   AND EXCHANGE COMMISSION OR ANY STATE SECURITIES COMMISSION PASSED UPON THE
ACCURACY OR ADEQUACY OF THIS PROSPECTUS. ANY REPRESENTATION TO THE CONTRARY IS A
                               CRIMINAL OFFENSE.
 
   INVESTORS SHOULD READ THIS PROSPECTUS AND RETAIN IT FOR FUTURE REFERENCE.
<PAGE>   121
 
(continued from previous page)
 
   
This Prospectus sets forth concisely the information concerning the Fund that a
prospective investor ought to know before investing. The Fund has filed with the
Securities and Exchange Commission (the "SEC") a Statement of Additional
Information, dated January 1, 1999, as amended or supplemented from time to time
(the "SAI"), which contains more detailed information about the Fund. The SAI is
incorporated into this Prospectus by reference. See page 39 for a further
description of the information set forth in the SAI. A copy of the SAI may be
obtained without charge by contacting the Shareholder Servicing Agent (see back
cover for address and phone number). The SEC maintains an Internet World Wide
Web site (http://www.sec.gov) that contains the SAI, materials that are
incorporated by reference into this Prospectus and the SAI, and other
information regarding the Fund. This Prospectus is available on the Adviser's
Internet World Wide Web site at http://www.mfs.com.
    
 
TABLE OF CONTENTS
 
   
<TABLE>
<CAPTION>
                                                                  PAGE
                                                                  ----
<S>  <C>                                                          <C>
1.   Expense Summary............................................    3
2.   Condensed Financial Information............................    5
3.   The Fund...................................................    8
4.   Investment Objective and Policies..........................    8
5.   Certain Securities and Investment Techniques...............    9
6.   Additional Risk Factors....................................   15
7.   Management of the Fund.....................................   18
8.   Year 2000 Issues...........................................   20
9.   Information Concerning Shares of the Fund..................   20
     Purchases..................................................   20
     Exchanges..................................................   27
     Redemptions and Repurchases................................   29
     Distribution Plan..........................................   31
     Distributions..............................................   34
     Tax Status.................................................   34
     Net Asset Value............................................   35
     Description of Shares, Voting Rights and Liabilities.......   35
     Performance Information....................................   36
     Expenses...................................................   36
     Provision of Annual and Semiannual Reports.................   37
10.  Shareholder Services.......................................   37
     Appendix A.................................................  A-1
</TABLE>
    
 
                                        2
<PAGE>   122
 
1.  EXPENSE SUMMARY
 
SHAREHOLDER TRANSACTION EXPENSES:
 
   
<TABLE>
<CAPTION>
                                            CLASS A      CLASS B      CLASS C
                                            -------      -------      -------
<S>                                         <C>          <C>          <C>
    Maximum Initial Sales Charge
      Imposed on Purchases of Fund
      Shares (as a percentage of
      offering price).................           5.75%        0.00%        0.00%
    Maximum Contingent Deferred Sales
      Charge (as a percentage of
      original purchase price or
      redemption proceeds, as                  See
      applicable).....................      Below(1)          4.00%        1.00%
ANNUAL OPERATING EXPENSES (AS A PERCENTAGE OF AVERAGE NET ASSETS):
    Management Fees...................           0.75%        0.75%        0.75%
    Rule 12b-1 Fees...................           0.25%(2)      1.00%(3)      1.00%(3)
    Other Expenses(4).................           0.43%        0.43%        0.43%
                                             -----        -----        -----
    Total Operating Expenses..........           1.43%        2.18%        2.18%
</TABLE>
    
 
- ---------------
(1) Purchases of $1 million or more are not subject to an initial sales charge;
    however, a contingent deferred sales charge (a "CDSC") of 1% will be imposed
    on such purchases in the event of certain redemption transactions within 12
    months following such purchases (see "Information Concerning Shares of the
    Fund -- Purchases").
(2) The Fund has adopted a distribution plan for its shares in accordance with
    Rule 12b-1 under the Investment Company Act of 1940, as amended (the "1940
    Act") (the "Distribution Plan"), which provides that it will pay
    distribution/service fees aggregating up to (but not necessarily all of)
    0.35% per annum of the average daily net assets attributable to the Class A
    shares. Payment of the 0.10% per annum Class A distribution fee will
    commence on such date as the Trustees of the Trust may determine.
    Distribution expenses paid under this Plan, together with the initial sales
    charge, may cause long-term shareholders to pay more than the maximum sales
    charge that would have been permissible if imposed entirely as an initial
    sales charge. See "Information Concerning Shares of the Fund -- Distribution
    Plan" below.
(3) The Fund's Distribution Plan provides that it will pay distribution/service
    fees aggregating up to (but not necessarily all of) 1.00% per annum of the
    average daily net assets attributable to Class B shares and Class C shares,
    respectively. Distribution expenses paid under the Distribution Plan with
    respect to Class B or Class C shares, together with any CDSC payable upon
    redemption of Class B and Class C shares, may cause long-term shareholders
    to pay more than the maximum sales charge that would have been permissible
    if imposed entirely as an initial sales charge. See "Information Concerning
    Shares of the Fund -- Distribution Plan" below.
(4) The Fund has an expense offset arrangement which reduces the Fund's
    custodian fee based upon the amount of cash maintained by the Fund with its
    custodian and dividend disbursing agent, and may enter into other such
    arrangements and directed brokerage arrangements (which would also have the
    effect of reducing the Fund's expenses). Any such reductions are not
    reflected under "Other Expenses."
 
                                        3
<PAGE>   123
 
                              EXAMPLE OF EXPENSES
 
An investor would pay the following dollar amounts of expenses on a $1,000
investment in the Fund, assuming (a) a 5% annual return and (b) redemption at
the end of each of the time periods indicated (unless otherwise noted):
 
   
<TABLE>
<CAPTION>
               PERIOD                  CLASS A      CLASS B         CLASS C
               ------                  -------    ------------    ------------
<S>                                    <C>        <C>     <C>     <C>     <C>
                                                          (1)              (1)
 1 year..............................   $ 71      $ 62    $ 22    $ 32    $ 22
 3 years.............................    100        98      68      68      68
 5 years.............................    131       137     117     117     117
10 years.............................    219       232(2)  232(2)  251     251
</TABLE>
    
 
- ---------------
(1) Assumes no redemption.
(2) Class B shares convert to Class A shares approximately eight years after
    purchase; therefore, years nine and ten reflect Class A expenses.
 
   
The purpose of the expense table above is to assist investors in understanding
the various costs and expenses that a shareholder of the Fund will bear directly
or indirectly. More complete descriptions of the following expenses of the Fund
are set forth in the following sections: (i) varying sales charges on share
purchases -- "Purchases"; (ii) varying CDSCs -- "Purchases"; (iii) management
fees -- "Management of the Fund"; and (iv) Rule 12b-1 (i.e., distribution
plan) fees -- "Distribution Plan."
    
 
THE "EXAMPLE" SET FORTH ABOVE SHOULD NOT BE CONSIDERED A REPRESENTATION OF PAST
OR FUTURE EXPENSES OF THE FUND; ACTUAL EXPENSES MAY BE GREATER OR LESS THAN
THOSE SHOWN.
 
                                        4
<PAGE>   124
 
2.  CONDENSED FINANCIAL INFORMATION
 
The following information has been audited since the inception of the Fund and
should be read in conjunction with the financial statements included in the
Fund's Annual Report to shareholders which are incorporated by reference into
the SAI. The financial statements for all but most recent six months are
included in reliance upon the report of the Fund's independent auditors, given
upon their authority as experts in accounting and auditing. The Fund's current
independent auditors are Deloitte & Touche LLP.
 
   
                              FINANCIAL HIGHLIGHTS
    
 
   
<TABLE>
<CAPTION>
                                               YEAR ENDED AUGUST 31,             PERIOD ENDED
                                     -----------------------------------------    AUGUST 31,
                                       1998       1997       1996       1995        1994*
                                       ----       ----       ----       ----     ------------
                                     CLASS A
                                     -------
<S>                                  <C>        <C>        <C>        <C>        <C>
Per share data (for a share
  outstanding throughout each
  period):
Net asset value -- beginning of
  period...........................  $   9.42   $   9.06   $  10.08   $   8.68     $   7.83
                                     --------   --------   --------   --------     --------
Income from investment
  operations# --
    Net investment loss**..........  $  (0.11)  $  (0.09)  $  (0.10)  $  (0.03)    $  (0.05)
    Net realized and unrealized
      gain (loss) on investments
      and foreign currency
      transactions.................     (1.31)      1.77       0.96       1.69         0.90
                                     --------   --------   --------   --------     --------
Total from investment operations...  $  (1.42)  $   1.68   $   0.86   $   1.66     $   0.85
                                     --------   --------   --------   --------     --------
Less distributions declared to
  shareholders from net realized
  gain on investment and foreign
  currency transactions............  $  (0.29)  $  (1.32)  $  (1.88)  $  (0.26)    $     --
                                     --------   --------   --------   --------     --------
Net asset value -- end of period...  $   7.71   $   9.42   $   9.06   $  10.08     $   8.68
                                     ========   ========   ========   ========     ========
Total return+++....................  (15.44)%     20.26%     10.55%     19.77%       10.86%++
Ratios (to average net assets)/
  Supplemental data**:
    Expenses##.....................     1.43%      1.41%      1.28%      1.29%        1.50%+
    Net investment loss............   (1.07)%    (1.09)%    (1.08)%    (0.40)%        (0.87)%+
Portfolio turnover.................      168%       170%       157%       218%          82%
Net assets at end of period (000
  omitted).........................  $ 36,413   $ 41,737   $ 35,098   $ 30,194     $ 17,776
</TABLE>
    
 
- ---------------
 
   
<TABLE>
<C>  <S>
  *  For the period from the commencement of the Fund's
     investment operations, December 1, 1993, through August 31,
     1994.
  +  Annualized.
 ++  Not annualized.
+++  Total returns for Class A shares do not include the
     applicable sales charge. If the charge had been included,
     the results would have been lower.
  #  Per share data are based on average shares outstanding.
 ##  For fiscal years ending after September 1, 1995, the Fund's
     expenses are calculated without reduction for fees paid
     indirectly.
 **  The investment adviser did not impose a portion of its
     management fee for the period indicated. If this fee had
     been incurred by the Fund, the net investment loss per share
     and the ratios would have been:
</TABLE>
    
 
   
<TABLE>
<S>                                   <C>        <C>        <C>        <C>        <C>
      Net investment loss...........  $     --   $     --   $     --   $     --   $  (0.08)
      Ratios (to average net
        assets):
        Expenses....................        --         --         --         --      2.03%+
        Net investment loss.........        --         --         --         --    (1.40)%+
</TABLE>
    
 
                                        5
<PAGE>   125
 
   
                              FINANCIAL HIGHLIGHTS
    
 
   
<TABLE>
<CAPTION>
                                                 YEAR ENDED AUGUST 31,             PERIOD ENDED
                                       -----------------------------------------    AUGUST 31,
                                         1998       1997       1996       1995        1994*
                                         ----       ----       ----       ----     ------------
                                       CLASS B
                                       --------
<S>                                    <C>        <C>        <C>        <C>        <C>
Per share data (for a share
  outstanding throughout each
  period):
Net asset value -- beginning of
  period.............................  $   9.27   $   8.93   $   9.94   $   8.59     $   7.83
                                       --------   --------   --------   --------     --------
Income from investment operations# --
    Net investment loss**............  $  (0.18)  $  (0.16)  $  (0.17)  $  (0.13)    $  (0.12)
    Net realized and unrealized gain
      (loss) on investments and
      foreign currency
      transactions...................     (1.28)      1.75       0.95       1.69         0.88
                                       --------   --------   --------   --------     --------
Total from investment operations.....  $  (1.46)  $   1.59   $   0.78   $   1.56     $   0.76
                                       --------   --------   --------   --------     --------
Less distributions declared to
  shareholders from net realized gain
  on investment and foreign currency
  transactions.......................  $  (0.21)  $  (1.25)  $  (1.79)  $  (0.21)    $     --
                                       --------   --------   --------   --------     --------
Net asset value -- end of period.....  $   7.60   $   9.27   $   8.93   $   9.94     $   8.59
                                       ========   ========   ========   ========     ========
Total return.........................  (16.05)%     19.36%      9.67%     18.75%        9.71%++
Ratios (to average net assets)/
  Supplemental data**:
    Expenses##.......................     2.18%      2.20%      2.13%      2.29%        2.57%+
    Net investment loss..............   (1.82)%    (1.87)%    (1.81)%    (1.44)%        (2.02)%+
Portfolio turnover...................      168%       170%       157%       218%          82%
Net assets at end of period (000
  omitted)...........................  $ 56,098   $ 73,940   $ 67,043   $ 61,742     $ 36,849
</TABLE>
    
 
- ---------------
 
   
<TABLE>
<C>  <S>
  *  For the period from the commencement of the Fund's
     investment operations, December 1, 1993, through August 31,
     1994.
  +  Annualized.
 ++  Not annualized.
  #  Per share data are based on average shares outstanding.
 ##  For fiscal years ending after September 1, 1995, the Fund's
     expenses are calculated without reduction for fees paid
     indirectly.
 **  The investment adviser did not impose a portion of its
     management fee for the period indicated. If this fee had
     been incurred by the Fund, the net investment loss per share
     and the ratios would have been:
</TABLE>
    
 
   
<TABLE>
<S>                                    <C>        <C>        <C>        <C>        <C>
      Net investment loss............  $     --   $     --   $     --   $     --   $  (0.15)
      Ratios (to average net assets):
        Expenses.....................        --         --         --         --      3.10%+
        Net investment loss..........        --         --         --         --    (2.56)%+
</TABLE>
    
 
                                        6
<PAGE>   126
 
   
                              FINANCIAL HIGHLIGHTS
    
 
   
<TABLE>
<CAPTION>
                                                  YEAR ENDED AUGUST 31,            PERIOD ENDED
                                         ---------------------------------------    AUGUST 31,
                                           1998       1997      1996      1995        1994*
                                           ----       ----      ----      ----     ------------
                                          CLASS C
                                          -------
<S>                                      <C>         <C>       <C>       <C>       <C>
Per share data (for a share outstanding
  throughout each period):
Net asset value -- beginning of
  period...............................  $    9.19   $  8.85   $  9.91   $  8.61     $  7.80
                                         ---------   -------   -------   -------     -------
Income from investment operations# --
    Net investment loss**..............  $   (0.18)  $ (0.16)  $ (0.17)  $ (0.14)    $ (0.04)
    Net realized and unrealized gain
      (loss) on investments and foreign
      currency transactions............      (1.26)     1.74      0.94      1.69        0.85
                                         ---------   -------   -------   -------     -------
Total from investment operations.......  $   (1.44)  $  1.58   $  0.77   $  1.55     $  0.81
                                         ---------   -------   -------   -------     -------
Less distributions declared to
  shareholders from net realized gain
  on investment and foreign currency
  transactions.........................  $   (0.22)  $ (1.24)  $ (1.83)  $ (0.25)         --
                                         ---------   -------   -------   -------     -------
Net asset value -- end of period.......  $    7.53   $  9.19   $  8.85   $  9.91     $  8.61
                                         =========   =======   =======   =======     =======
Total return...........................   (16.00)%    19.44%     9.60%    18.63%      10.38%++
Ratios (to average net assets)/
  Supplemental data**:
    Expenses##.........................      2.18%     2.16%     2.17%     2.30%       2.50%+
    Net investment loss................    (1.82)%   (1.79)%   (1.90)%   (1.55)%     (2.22)%+
Portfolio turnover.....................       168%      170%      157%      218%         82%
Net assets at end of period (000
  omitted).............................  $   5,607   $ 5,796   $ 6,860   $ 3,209     $    87
</TABLE>
    
 
- ---------------
 
   
<TABLE>
<C>  <S>
  *  For the period from the inception of Class C shares, August
     1, 1994, through August 31, 1994.
  +  Annualized.
 ++  Not annualized.
  #  Per share data are based on average shares outstanding.
 ##  For fiscal years ending after September 1, 1995, the Fund's
     expenses are calculated without reduction for fees paid
     indirectly.
 **  The investment adviser did not impose a portion of its
     management fee for the period indicated. If this fee had
     been incurred by the Fund, the net investment loss per share
     and the ratios would have been:
</TABLE>
    
 
   
<TABLE>
<S>                                      <C>         <C>       <C>       <C>       <C>
      Net investment loss..............  $      --   $    --   $    --   $    --     $ (0.05)
      Ratios(to average net assets):
        Expenses.......................         --        --        --        --       3.03%+
        Net investment loss............         --        --        --        --       (2.71)%+
</TABLE>
    
 
                                        7
<PAGE>   127
 
3.  THE FUND
 
The Fund is a non-diversified series of the Trust, an open-end management
investment company which was organized as a business trust under the laws of The
Commonwealth of Massachusetts in 1975. The Trust presently consists of four
series, each of which represents a portfolio with separate investment objectives
and policies. Shares of the Fund are continuously sold to the public and the
Fund then uses the proceeds to buy securities for its portfolio. Three classes
of shares of the Fund are currently offered to the general public. Class A
shares are offered at net asset value plus an initial sales charge up to a
maximum of 5.75% of the offering price (or a CDSC of 1.00% upon redemption
during the first year in the case of purchases of $1 million or more and certain
purchase by retirement plans) and subject to an annual distribution fee and
service fee up to a maximum of 0.35% per annum. Class B shares are offered at
net asset value without an initial sales charge but are subject to a CDSC upon
redemption (declining from 4% during the first year to 0% after six years) and
an annual distribution fee and a service fee up to a maximum of 1.00% per annum;
Class B shares will convert to Class A shares approximately eight years after
purchase. Class C shares are offered at net asset value without an initial sales
charge but are subject to a CDSC of 1.00% upon redemption during the first year
and an annual distribution fee and service fee of 1.00% per annum. Class C
shares do not convert to any other class of shares of the Fund. In addition, the
Fund offers an additional class of shares, Class I shares, exclusively to
certain institutional investors. Class I shares are made available by means of a
separate Prospectus supplement provided to institutional investors eligible to
purchase Class I shares and are offered at net asset value without an annual
distribution and service fee.
 
The Trust's Board of Trustees provides broad supervision over the affairs of the
Fund. The Adviser is responsible for the management of the Fund's assets and the
officers of the Trust are responsible for the Fund's operations. The Adviser
manages the portfolio from day to day in accordance with the Fund's investment
objective and policies. The selection of investments and the way they are
managed depend on conditions and trends in the economy and the financial
marketplaces. The Fund also offers to buy back (redeem) its shares from its
shareholders at any time at net asset value, less any applicable CDSC.
 
4.  INVESTMENT OBJECTIVE AND POLICIES
 
INVESTMENT OBJECTIVE -- The Fund's investment objective is to seek to obtain
long-term growth of capital.
 
   
INVESTMENT POLICIES -- The Fund seeks to achieve its objective by investing,
under normal market conditions, at least 65% of its total assets in equity
securities of companies with medium market capitalization which the Adviser
believes have above-average growth potential (see "Certain Securities and
Investment Techniques -- Equity Securities" below). Medium market capitalization
companies are those whose market capitalization equals or exceeds $250 million
but does not exceed the top range of the Russell Midcap(TM) Growth Index at the
time of the Fund's investment. The Index is a widely recognized, unmanaged index
of mid-cap common stock prices. Companies whose capitalization falls below $250
million or exceeds the top of the Russell Midcap(TM) Growth Index range after
purchase continue to be considered medium-capitalization companies for purposes
of the Fund's 65% policy. The Fund may, but is not required to, purchase
securities of companies included in the Russell Midcap(TM) Growth Index. The
Index is only used by the Fund for purposes of defining the market
capitalization range of
    
 
                                        8
<PAGE>   128
 
   
companies in which the Fund will invest; it is not intended to be used as a
benchmark against which the Fund compares its investment performance. As of
October 30, 1998, the top of the Russell Midcap(TM) Growth Index was $25.8
billion.
    
 
   
Consistent with its investment objective, the Fund may invest in fixed income
securities and up to 20% of its net assets in non-convertible fixed income
securities that are in the lower rating categories (rated Ba or lower by Moody's
Investors Service, Inc. ("Moody's") or BB or lower by Standard & Poor's Ratings
Services ("S&P"), Duff & Phelps Credit Rating Co. ("Duff & Phelps") or Fitch
IBCA ("Fitch") and comparable unrated securities (commonly known as "junk
bonds") (see "Certain Securities and Investment Techniques -- "Fixed Income
Securities" and "Additional Risk Factors -- Lower Rated Fixed Income Securities"
below) and may also invest up to 35% (and generally expects to invest up to 20%)
of its net assets in foreign securities which are not traded on a U.S. exchange
(not including American Depositary Receipts)(see "Additional Risk
Factors -- Foreign Securities" below).
    
 
The Fund may engage in certain securities, transactions and investment
techniques as described under the caption "Certain Securities and Investment
Techniques" below and "Certain Securities and Investment Techniques" in the SAI.
The Fund's investments are subject to certain risks, as described in the
above-referenced sections of this Prospectus and the SAI and as described below
under the caption "Additional Risk Factors."
 
5.  CERTAIN SECURITIES AND INVESTMENT TECHNIQUES
 
Additional information about certain of these securities and investment
techniques can be found under the caption "Certain Securities and Investment
Techniques" in the SAI.
 
EQUITY SECURITIES:  The Fund may invest in all types of equity securities,
including the following: common stocks, preferred stocks and preference stocks;
securities such as bonds, warrants or rights that are convertible into stocks;
and depository receipts for those securities. These securities may be listed on
securities exchanges, traded in various over-the-counter markets or have no
organized markets.
 
FIXED INCOME SECURITIES:  Debt securities in which the Fund may invest include
all types of long- or short-term debt obligations, such as bonds, debentures,
notes and commercial paper. Fixed income securities in which the Fund may invest
include securities in the lower rating categories of recognized rating agencies
(and comparable unrated securities) (see "Additional Risk Factors -- Lower Rated
Fixed Income Securities" below). Fixed income securities in which the Fund may
invest also include zero coupon bonds, deferred interest bonds and bonds on
which the interest is payable in kind. Such investments involve certain risks.
 
INVESTMENTS FOR TEMPORARY DEFENSIVE PURPOSES:  When the Adviser believes that
investing for defensive purposes is appropriate, such as during periods of
unusual market conditions, part or all of the Fund's assets may be temporarily
invested in cash (including foreign currency) or cash equivalent short-term
obligations including, but not limited to, certificates of deposit, commercial
paper, short-term notes, obligations issued or guaranteed by the U.S. Government
or any of its agencies or instrumentalities and repurchase agreements.
 
EMERGING MARKET SECURITIES:  Consistent with the Fund's objective and policies,
the Fund may invest in securities of issuers whose principal activities are
located in emerging market countries. Emerging market countries include any
country determined by the Adviser to have an emerging
 
                                        9
<PAGE>   129
 
market economy, taking into account a number of factors, including whether the
country has a low- to middle-income economy according to the International Bank
for Reconstruction and Development, the country's foreign currency debt rating,
its political and economic stability and the development of its financial and
capital markets. The Adviser determines whether an issuer's principal activities
are located in an emerging market country by considering such factors as its
country of organization, the principal trading market for its securities and the
source of its revenues and location of its assets. The issuer's principal
activities generally are deemed to be located in a particular country if: (a)
the security is issued or guaranteed by the government of that country or any of
its agencies, authorities or instrumentalities; (b) the issuer is organized
under the laws of, and maintains a principal office in, that country; (c) the
issuer has its principal securities trading market in that country; (d) the
issuer derives 50% or more of its total revenues from goods sold or services
performed in that country; or (e) the issuer has 50% or more of its assets in
that country.
 
BRADY BONDS:  The Fund may invest in Brady Bonds, which are securities created
through the exchange of existing commercial bank loans to public and private
entities in certain emerging markets for new bonds in connection with debt
restructurings under a debt restructuring plan introduced by former U.S.
Secretary of the Treasury, Nicholas F. Brady (the "Brady Plan"). Brady Plan debt
restructurings have been implemented to date in Argentina, Brazil, Bulgaria,
Costa Rica, Croatia, the Dominican Republic, Ecuador, Jordan, Mexico, Morocco,
Nigeria, Panama, Peru, the Philippines, Poland, Slovenia, Uruguay and Venezuela.
Brady Bonds have been issued only recently, and for that reason do not have a
long payment history. Brady Bonds may be collateralized or uncollateralized, are
issued in various currencies (but primarily the U.S. dollar) and are actively
traded in over-the-counter secondary markets. U.S. dollar-denominated,
collateralized Brady Bonds, which may be fixed-rate bonds or floating-rate
bonds, are generally collateralized in full as to principal by U.S. Treasury
zero coupon bonds having the same maturity as the bonds. Brady Bonds are often
viewed as having three or four valuation components: the collateralized
repayment of principal at final maturity; the collateralized interest payments;
the uncollateralized interest payments; and any uncollateralized repayment of
principal at maturity (these uncollateralized amounts constituting the "residual
risk"). In light of the residual risk of Brady Bonds and the history of defaults
of countries issuing Brady Bonds with respect to commercial bank loans by public
and private entities, investments in Brady Bonds may be viewed as speculative.
 
AMERICAN DEPOSITARY RECEIPTS:  The Fund may invest in American Depositary
Receipts ("ADRs") which are certificates issued by a U.S. depository (usually a
bank) and represent a specified quantity of shares of an underlying non-U.S.
stock on deposit with a custodian bank as collateral. Because ADRs trade on
United States securities exchanges, the Adviser does not treat them as foreign
securities. However, they are subject to many of the risks of foreign securities
such as changes in exchange rates and more limited information about foreign
issuers.
 
REPURCHASE AGREEMENTS:  The Fund may enter into repurchase agreements in order
to earn income on available cash or as a temporary defensive measure. Under a
repurchase agreement, the Fund acquires securities subject to the seller's
agreement to repurchase at a specified time and price. If the seller becomes
subject to a proceeding under the bankruptcy laws or its assets are otherwise
subject to a stay order, the Fund's right to liquidate the securities may be
restricted
 
                                       10
<PAGE>   130
 
(during which time the value of the securities could decline). As discussed in
the SAI, the Fund has adopted certain procedures intended to minimize risk.
 
LENDING OF SECURITIES:  The Fund may seek to increase its income by lending
portfolio securities. Such loans will usually be made only to member firms (and
subsidiaries thereof) of the New York Stock Exchange (the "Exchange") and to
member banks of the Federal Reserve System, and would be required to be secured
continuously by collateral in cash, U.S. Government securities or an irrevocable
letter of credit maintained on a current basis at an amount at least equal to
the market value of the securities loaned. The Fund will continue to collect the
equivalent of interest on the securities loaned and will also receive either
interest (through investment in cash collateral) or a fee (if the collateral is
U.S. Government securities or a letter of credit).
 
"WHEN-ISSUED" SECURITIES:  The Fund may purchase securities on a "when-issued"
or on a "forward delivery" basis, which means that the securities will be
delivered to the Fund at a future date usually beyond customary settlement time.
The commitment to purchase a security for which payment will be made on a future
date may be deemed a separate security. The Fund does not pay for the securities
until received, and does not start earning interest on the securities until the
contractual settlement date. While awaiting delivery of securities purchased on
such bases, the Fund will segregate liquid assets sufficient to cover its
commitments. Although the Fund does not intend to make such purchases for
speculative purposes, purchases of securities on such bases may involve more
risk than other types of purchases.
 
INDEXED SECURITIES:  The Fund may invest in indexed securities whose value is
linked to foreign currencies, interest rates, commodities, indices, or other
financial indicators. Most indexed securities are short to intermediate term
fixed-income securities whose values at maturity (i.e., principal value) or
interest rates rise or fall according to changes in the value of one or more
specified underlying instruments. Indexed securities may be positively or
negatively indexed (i.e., their principal value or interest rates may increase
or decrease if the underlying instrument appreciates), and may have return
characteristics similar to direct investments in the underlying instrument or to
one or more options on the underlying instrument. Indexed securities may be more
volatile than the underlying instrument itself and could involve the loss of all
or a portion of the principal amount of or interest on the investment.
 
MORTGAGE "DOLLAR ROLL" TRANSACTIONS:  The Fund may enter into mortgage "dollar
roll" transactions with selected banks and broker-dealers pursuant to which the
Fund sells mortgage-backed securities for delivery in the future (generally
within 30 days) and simultaneously contracts to repurchase substantially similar
(same type, coupon and maturity) securities on a specified future date. The Fund
will only enter into covered rolls. A "covered roll" is a specific type of
dollar roll for which there is an offsetting cash position or a cash equivalent
security position which matures on or before the forward settlement date of the
dollar roll transaction.
 
RESTRICTED SECURITIES:  The Fund may also purchase securities that are not
registered under the Securities Act of 1933 ("1933 Act") ("restricted
securities"), including those that can be offered and sold to "qualified
institutional buyers" under Rule 144A under the 1933 Act ("Rule 144A
securities"). A determination is made based upon a continuing review of the
trading markets for a specific Rule 144A security, whether such security is
liquid and thus not subject to the Fund's limitations on investing not more than
15% of its net assets in illiquid investments. The Board of Trustees has adopted
guidelines and delegated to MFS the daily function of
 
                                       11
<PAGE>   131
 
   
determining and monitoring the liquidity of Rule 144A securities. The Board,
however, retains oversight of the liquidity determinations, focusing on factors
such as valuation, liquidity and availability of information. Investing in Rule
144A securities could have the effect of decreasing the level of liquidity in
the Fund to the extent that qualified institutional buyers become for a time
uninterested in purchasing Rule 144A securities held in the Fund's portfolio.
Subject to the Fund's 15% limitation on investments in illiquid investments, the
Fund may also invest in restricted securities that may not be sold under Rule
144A, which presents certain risks. As a result, the Fund might not be able to
sell these securities when the Adviser wishes to do so, or might have to sell
them at less than fair value. In addition, market quotations are less readily
available. Therefore, judgment may at times play a greater role in valuing these
securities than in the case of unrestricted securities.
    
 
CORPORATE ASSET-BACKED SECURITIES:  The Fund may invest in corporate
asset-backed securities. These securities, issued by trusts and special purpose
corporations, are backed by a pool of assets, such as credit card or automobile
loan receivables, representing the obligations of a number of different parties.
Corporate asset-backed securities present certain risks. For instance, in the
case of credit card receivables, these securities may not have the benefit of
any security interest in the related collateral. See the SAI for further
information on these securities.
 
OPTIONS ON SECURITIES:  The Fund may write (sell) covered put and call options
on securities and purchase put and call options on securities. The Fund will
write such options for the purpose of increasing its return and/or to protect
the value of its portfolio. In particular, where the Fund writes an option which
expires unexercised or is closed out by the Fund at a profit, it will retain the
premium paid for the option, which will increase its investment income and will
offset in part the reduced value of a portfolio security in connection with
which the option may have been written or the increased cost of portfolio
securities to be acquired. However, the writing of options constitutes only a
partial hedge, up to the amount of the premium, less any transaction costs. In
contrast, if the price of the security underlying the option moves adversely to
the Fund's position, the option may be exercised and the Fund will be required
to purchase or sell the security at a disadvantageous price, resulting in losses
which may only be partially offset by the amount of the premium. The Fund may
also write combinations of put and call options on the same security, known as
"straddles." Such transactions can generate additional premium income but also
present increased risk.
 
The Fund may purchase put or call options in anticipation of declines in the
value of portfolio securities or increases in the value of securities to be
acquired. In the event that such declines or increases occur, the Fund may be
able to offset the resulting adverse effect on its portfolio, in whole or in
part, through the options purchased. The risk assumed by the Fund in connection
with such transactions is limited to the amount of the premium and related
transaction costs associated with the option, although the Fund may be required
to forfeit such amounts in the event that the prices of securities underlying
the options do not move in the direction or to the extent anticipated.
 
The Fund may also enter into options on the yield "spread," or yield
differential, between two securities, a transaction referred to as a "yield
curve" option, for hedging purposes and non-hedging purposes (which may be
speculative). In contrast to other types of options, a yield curve option is
based on the difference between the yields of designated securities rather than
the
 
                                       12
<PAGE>   132
 
actual prices of the individual securities, and is settled through cash
payments. Accordingly, a yield curve option is profitable to the holder if this
differential widens (in the case of a call) or narrows (in the case of a put),
regardless of whether the yields of the underlying securities increase or
decrease. Yield curve options written by the Fund will be covered as described
in the SAI. The trading of yield curve options is subject to all the risks
associated with trading other types of options, as discussed below under "Risk
Factors" and in the SAI. In addition, such options present risks of loss even if
the yield on one of the underlying securities remains constant, if the spread
moves in a direction or to an extent which was not anticipated.
 
OPTIONS ON STOCK INDICES:  The Fund may write (sell) covered call and put
options and purchase call and put options on stock indices. The Fund may write
options on stock indices for the purpose of increasing its gross income and to
protect its portfolio against declines in the value of securities it owns or
increases in the value of securities to be acquired. When the Fund writes an
option on a stock index, and the value of the index moves adversely to the
holder's position, the option will not be exercised, and the Fund will either
close out the option at a profit or allow it to expire unexercised. The Fund
will thereby retain the amount of the premium, which will increase its gross
income and offset part of the reduced value of portfolio securities or the
increased cost of securities to be acquired. Such transactions, however, will
constitute only partial hedges against adverse price fluctuations, since any
such fluctuations will be offset only to the extent of the premium received by
the Fund for the writing of the option. In addition, if the value of an
underlying index moves adversely to the Fund's option position, the option may
be exercised, and the Fund will experience a loss which may only be partially
offset by the amount of the premium received.
 
The Fund may also purchase put or call options on stock indices in order,
respectively, to hedge its investments against a decline in value or to attempt
to reduce the risk of missing a market or industry segment advance. The Fund's
possible loss in either case will be limited to the premium paid for the option,
plus related transaction costs.
 
OPTIONS ON FOREIGN CURRENCIES:  The Fund may also purchase and write options on
foreign currencies ("Options on Foreign Currencies") for the purpose of
protecting against declines in the dollar value of portfolio securities and
against increases in the dollar cost of securities to be acquired. As in the
case of other types of options, however, the writing of an Option on Foreign
Currency will constitute only a partial hedge, up to the amount of the premium
received, and the Fund may be required to purchase or sell foreign currencies at
disadvantageous exchange rates, thereby incurring losses. The purchase of an
Option on Foreign Currency may constitute an effective hedge against
fluctuations in exchange rates although, in the event of rate movements adverse
to the Fund's position, it may forfeit the entire amount of the premium paid for
the option plus related transaction costs. The Fund may also choose to, or be
required to, receive delivery of the foreign currencies underlying Options on
Foreign Currencies it has entered into. Under certain circumstances, such as
where the Adviser believes that the applicable exchange rate is unfavorable at
the time the currencies are received or the Adviser anticipates, for any other
reason, that the exchange rate will improve, the Fund may hold such currencies
for an indefinite period of time.
 
FUTURES CONTRACTS:  The Fund may enter into stock index and foreign currency
futures contracts (collectively "Futures Contracts"). Such transactions will be
entered into for hedging purposes,
 
                                       13
<PAGE>   133
 
   
in order to protect the Fund's current or intended investments from the effects
of changes in exchange rates or declines in the stock market. The Fund will
incur brokerage fees when it purchases and sells Futures Contracts, and will be
required to maintain margin deposits. In addition, Futures Contracts entail
risks. Although the Adviser believes that use of such contracts will benefit the
Fund, if its investment judgment about the general direction of exchange rates
or the stock market is incorrect, the Fund's overall performance may be poorer
than if it had not entered into any such contract and the Fund may realize a
loss. Futures Contracts may also be entered into for non-hedging purposes, to
the extent permitted by applicable law, which involves greater risks and could
result in losses which are not offset by gains on other portfolio assets.
    
 
OPTIONS ON FUTURES CONTRACTS:  The Fund may purchase and write options on
Futures Contracts ("Options on Futures Contracts") in order to protect against
declines in the values of portfolio securities or against increases in the cost
of securities to be acquired. Purchases of Options on Futures Contracts may
present less risk in hedging the Fund's portfolio than the purchase or sale of
the underlying Futures Contracts because the potential loss is limited to the
amount of the premium plus related transaction costs, although it may be
necessary to exercise the option to realize any profit, which results in the
establishment of a futures position. The writing of Options on Futures
Contracts, however, does not present less risk than the trading of Futures
Contracts and will constitute only a partial hedge, up to the amount of the
premium received. In addition, if an option is exercised, the Fund may suffer a
loss on the transaction. Options on Futures Contracts may also be entered into
for non-hedging purposes (which may be speculative) to the extent permitted
under applicable law, which involves greater risks and could result in losses
which are not offset by gains on other portfolio assets.
 
FORWARD CONTRACTS:  The Fund may enter into forward foreign currency exchange
contracts for the purchase or sale of a fixed quantity of a foreign currency at
a future date ("Forward Contracts"). The Fund may enter into Forward Contracts
for hedging purposes as well as for non-hedging purposes (which may be
speculative). By entering into transactions in Forward Contracts, for hedging
purposes, the Fund may be required to forego the benefits of advantageous
changes in exchange rates and, in the case of Forward Contracts entered into for
non-hedging purposes, the Fund may sustain losses which will reduce its gross
income. Such transactions, therefore, could be considered speculative. Forward
Contracts are traded over-the-counter and not on organized commodities or
securities exchanges. As a result, Forward Contracts operate in a manner
distinct from exchange-traded instruments, and their use involves certain risks
beyond those associated with transactions in Futures Contracts or options traded
on exchanges. The Fund may choose to, or be required to, receive delivery of the
foreign currencies underlying Forward Contracts into which it has entered. Under
certain circumstances, such as where the Adviser believes that the applicable
exchange rate is unfavorable at the time the currencies are received or the
Adviser anticipates, for any other reason, that the exchange rate will improve,
the Fund may hold such currencies for an indefinite period of time. The Fund may
also enter into a Forward Contract on one currency to hedge against risk of loss
arising from fluctuations in the value of a second currency (referred to as a
"cross hedge") if, in the judgment of the Adviser, a reasonable degree of
correlation can be expected between movements in the values of the two
currencies. The Fund has established procedures which require use of segregated
assets or "cover" in connection with the purchase and sale of such contracts.
 
                                       14
<PAGE>   134
 
6.  ADDITIONAL RISK FACTORS
 
The following discussion of additional risk factors supplements the risk factors
described above. Additional information concerning risk factors can be found
under the caption "Certain Securities and Investment Techniques" in the SAI.
 
MEDIUM CAPITALIZATION STOCKS:  Investing in medium capitalization stocks may
involve greater risk than investing in large capitalization stocks, since they
can be subject to more abrupt or erratic movements. However, they tend to
involve less risk than stocks of small capitalization companies.
 
EMERGING GROWTH COMPANIES:  The stocks of companies in which the Fund may invest
may be early in their life cycle but have the potential to become major
enterprises (emerging growth companies). Such companies generally may be of any
size, would be expected to show earnings growth over time that is well above the
growth rate of the overall economy and the rate of inflation, and would have the
products, technologies, management and market and other opportunities which are
usually necessary to become more widely recognized as growth companies. Emerging
growth companies in which the Fund invests may be established companies whose
rates of earnings growth are expected to accelerate because of special factors,
such as rejuvenated management, new products, changes in consumer demand, or
basic changes in economic environment.
 
The nature of investing in emerging growth companies involves greater risk than
is customarily associated with investments in other companies which do not have
emerging growth characteristics. Emerging growth companies often have limited
product lines, markets or financial resources, and they may be dependent on the
management abilities of a limited number of people. In addition, there may be
less research available on many promising emerging growth companies, making it
more difficult to find and analyze these companies. The securities of emerging
growth companies may have limited marketability and may be subject to more
abrupt or erratic market movements than securities of more established growth
companies or the market averages in general. Shares of the Fund, therefore, are
subject to greater fluctuation in value than shares of a conservative equity
fund or of a growth fund which invests entirely in proven growth stocks.
 
FIXED INCOME SECURITIES:  To the extent the Fund invests in fixed income
securities, the net asset value of the Fund may change as the general levels of
interest rates fluctuate. When interest rates decline, the value of fixed income
securities can be expected to rise. Conversely, when interest rates rise, the
value of fixed income securities can be expected to decline.
 
   
LOWER RATED FIXED INCOME SECURITIES:  The Fund may invest up to 20% of its net
assets in non-convertible fixed income securities that are in the lower rating
categories (rated Ba or lower by Moody's or BB or lower by S&P, Duff & Phelps or
Fitch) and comparable unrated securities (commonly known as "junk bonds"). These
securities are considered speculative and, while generally providing greater
income than investments in higher rated securities, will involve greater risk of
principal and income (including the possibility of default or bankruptcy of the
issuers of such securities) and may involve greater volatility of price than
securities in the higher rating categories. The market for these lower rated
fixed income securities may be less liquid than the market for investment grade
fixed income securities. Furthermore, the liquidity of these lower rated
securities may be affected by the market's perception of their credit quality.
Therefore, judgment may at times play a greater role in valuing these securities
than in the case
    
 
                                       15
<PAGE>   135
 
of investment grade fixed income securities, and it also may be more difficult
during certain adverse market conditions to sell these lower rated securities to
meet redemption requests or to respond to changes in the market.
 
   
The Fund may also invest in fixed income securities rated Baa by Moody's or BBB
by S&P, Duff & Phelps or Fitch and comparable unrated securities. These
securities, while normally exhibiting adequate protection parameters, have
speculative characteristics and changes in economic conditions or other
circumstances are more likely to lead to a weakened capacity to make principal
and interest payments than in the case of higher grade fixed income securities.
    
 
FOREIGN SECURITIES:  Investing in securities of foreign issuers generally
involves risks not ordinarily associated with investing in securities of
domestic issuers. These include changes in currency rates, exchange control
regulations, governmental administration or economic or monetary policy (in the
United States or abroad) or circumstances in dealings between nations. Costs may
be incurred in connection with conversions between various currencies. Special
considerations may also include more limited information about foreign issuers,
higher brokerage costs, different accounting standards and thinner trading
markets. Foreign securities markets may also be less liquid, more volatile and
less subject to government supervision than in the United States. Investments in
foreign countries could be affected by other factors including expropriation,
confiscatory taxation and potential difficulties in enforcing contractual
obligations and could be subject to extended settlement periods. The Fund may
hold foreign currency received in connection with investments in foreign
securities when, in the judgment of the Adviser, it would be beneficial to
convert such currency into U.S. dollars at a later date, based on anticipated
changes in the relevant exchange rate. The Fund may also hold foreign currency
in anticipation of purchasing foreign securities. See the SAI for further
discussion of foreign securities and the holding of foreign currency, as well as
the associated risks.
 
EMERGING MARKETS:  The risks of investing in foreign securities may be
intensified in the case of investments in emerging markets. Securities of many
issuers in emerging markets may be less liquid and more volatile than securities
of comparable domestic issuers. Emerging markets also have different clearance
and settlement procedures, and in certain markets there have been times when
settlements have been unable to keep pace with the volume of securities
transactions, making it difficult to conduct such transactions. Delays in
settlement could result in temporary periods when a portion of the assets of the
Fund is uninvested and no return is earned thereon. The inability of the Fund to
make intended security purchases due to settlement problems could cause the Fund
to miss attractive investment opportunities. Inability to dispose of portfolio
securities due to settlement problems could result in losses to the Fund due to
subsequent declines in value of the portfolio security, a decrease in the level
of liquidity in the Fund's portfolio, or, if the Fund has entered into a
contract to sell the security, in possible liability to the purchaser. Certain
markets may require payment for securities before delivery, and in such markets
the Fund bears the risk that the securities will not be delivered and that the
Fund's payments will not be returned. Securities prices in emerging markets can
be significantly more volatile than in the more developed nations of the world,
reflecting the greater uncertainties of investing in less established markets
and economies. In particular, countries with emerging markets may have
relatively unstable governments, present the risk of nationalization of
businesses, restrictions on foreign ownership, or prohibitions of repatriation
of assets, and may have less protection of property rights than more developed
countries. The economies of
                                       16
<PAGE>   136
 
countries with emerging markets may be predominantly based on only a few
industries, may be highly vulnerable to changes in local or global trade
conditions, and may suffer from extreme and volatile debt burdens or inflation
rates. Local securities markets may trade a small number of securities and may
be unable to respond effectively to increases in trading volume, potentially
making prompt liquidation of substantial holdings difficult or impossible at
times. Securities of issuers located in countries with emerging markets may have
limited marketability and may be subject to more abrupt or erratic price
movements.
 
Certain emerging markets may require governmental approval for the repatriation
of investment income, capital or the proceeds of sales of securities by foreign
investors. In addition, if a deterioration occurs in an emerging market's
balance of payments or for other reasons, a country could impose temporary
restrictions on foreign capital remittances. The Fund could be adversely
affected by delays in, or a refusal to grant, any required governmental approval
for repatriation of capital, as well as by the application to the Fund of any
restrictions on investments.
 
Investment in certain foreign emerging market debt obligations may be restricted
or controlled to varying degrees. These restrictions or controls may at times
preclude investment in certain foreign emerging market debt obligations and
increase the expenses of the Fund. See the SAI for a further discussion of
emerging market securities as well as the associated risks.
 
OPTIONS, FUTURES CONTRACTS AND FORWARD CONTRACTS:  Although the Fund will enter
into certain transactions in options, Futures Contracts, Options on Futures
Contracts and Options on Foreign Currencies for hedging purposes, such
transactions nevertheless involve certain risks. For example, a lack of
correlation between the instrument underlying an option on Futures Contract and
the assets being hedged, or unexpected adverse price movements, could render the
Fund's hedging strategy unsuccessful and could result in losses. The Fund also
may enter into transactions in options, Futures Contracts, Options or Futures
Contracts and Forward Contracts for other than hedging purposes, which involves
greater risk. In particular, such transactions may result in losses for the Fund
which are not offset by gains on other portfolio positions, thereby reducing
gross income. In addition, foreign currency markets may be extremely volatile
from time to time. There also can be no assurance that a liquid secondary market
will exist for any contract purchased or sold, and the Fund may be required to
maintain a position until exercise or expiration, which could result in losses.
The SAI contains a description of the nature and trading mechanics of options,
Futures Contracts, Options on Futures Contracts, Forward Contracts and Options
on Foreign Currencies, and includes a discussion of the risks related to
transactions therein.
 
Transactions in Forward Contracts may be entered into only in the
over-the-counter market. Futures Contracts and Options on Futures Contracts may
be entered into on U.S. exchanges regulated by the Commodity Futures Trading
Commission and on foreign exchanges. In addition, the securities underlying
options, Futures Contracts and Options on Futures Contracts traded by the Fund
will include both domestic and foreign securities.
 
NON-DIVERSIFIED STATUS:  The Fund has registered as a "non-diversified"
investment company. As a result, the Fund is limited as to the percentage of its
assets which may be invested in the securities of any one issuer only by its own
investment restrictions and the diversification requirements imposed by the
Internal Revenue Code of 1986, as amended (the "Code"). U.S. Government
securities which are generally considered free of credit risk and are assured as
to
 
                                       17
<PAGE>   137
 
payment of principal and interest if held to maturity are not subject to any
investment limitation. Since the Fund may invest a relatively high percentage of
its assets in a limited number of issuers, the Fund may be more susceptible to
any single economic, political or regulatory occurrence and to the financial
conditions of the issuers in which it invests. For these reasons, an investment
in shares of the Fund should not be considered to constitute a complete
investment program.
                            ------------------------
 
PORTFOLIO TRADING:  The primary consideration in placing portfolio security
transactions with broker-dealers for execution is to obtain and maintain the
availability of execution at the most favorable prices and in the most effective
manner possible. Consistent with the foregoing primary consideration, the
Conduct Rules of the National Association of Securities Dealers, Inc. (the
"NASD"), and such other policies as the Trustees may determine, the Adviser may
consider sales of shares of the Fund and of the other investment company clients
of MFD, the Fund's distributor, as a factor in the selection of broker-dealers
to execute the Fund's portfolio transactions. From time to time, the Adviser may
direct certain portfolio transactions to broker-dealer firms which, in turn,
have agreed to pay a portion of the Fund's operating expenses (e.g., fees
charged by the custodian of the Fund's assets). For a further discussion of
portfolio trading, see "Portfolio Transactions and Brokerage Commissions" in the
SAI.
 
   
While it is not generally the Fund's policy to invest or trade for short-term
profits, the Fund may dispose of a portfolio security whenever the Adviser is of
the opinion that such security no longer has an appropriate appreciation
potential or when another security appears to offer relatively greater
appreciation potential. Portfolio changes are made without regard to the length
of time a security has been held, or whether a sale would result in a profit or
loss. Therefore, the rate of portfolio turnover is not a limiting factor when a
change in the portfolio is otherwise appropriate. For the fiscal year ended
August 31, 1998, the Fund had a portfolio turnover rate of over 100%.
Transaction costs incurred by the Fund and the realized capital gains and losses
of the Fund may be greater than that of a Fund with a lesser portfolio turnover
rate.
    
                            ------------------------
 
The investment objective and policies described above, including Options,
Options on Foreign Currency, Futures Contracts, Options on Futures Contracts and
Forward Contracts, are not fundamental and may be changed without shareholder
approval. A change in the Fund's investment objective may result in the Fund
having an investment objective different from the objective which the
shareholder considered appropriate at the time of investment in the Fund.
 
The SAI includes a discussion of other investment policies and a listing of
specific investment restrictions which govern the Fund's investment policies.
The specific investment restrictions listed in the SAI may be changed without
shareholder approval unless indicated otherwise (see "Investment Restrictions"
in the SAI). Except with respect to the Fund's policy on borrowing and investing
in illiquid securities, the Fund's investment limitations, policies and rating
standards are adhered to at the time of purchase or utilization of assets; a
subsequent change in circumstances will not be considered to result in a
violation of policy.
 
7.  MANAGEMENT OF THE FUND
 
INVESTMENT ADVISER -- The Adviser manages the Fund pursuant to an Investment
Advisory Agreement, dated October 20, 1993 (the "Advisory Agreement"). Under the
Advisory Agree-
 
                                       18
<PAGE>   138
 
   
ment, the Adviser provides the Fund with overall investment advisory services.
Mark Regan has been the Fund's portfolio manager since the Fund's inception. Mr.
Regan is a Vice President of the Adviser and has been employed as a portfolio
manager by the Adviser since 1989. Subject to such policies as the Trustees may
determine, the Adviser makes investment decisions for the Fund. For these
services and facilities, the Adviser receives a management fee, computed and
paid monthly, equal to 0.75% of the average daily net assets of the Fund on an
annualized basis. For the Fund's fiscal year ended August 31, 1998, management
fees paid to MFS under the Advisory Agreement were $972,215.
    
 
   
MFS also serves as investment adviser to each of the other funds in the MFS
Family of Funds (the "MFS Funds") and to MFS(R)/Sun Life Series Trust, MFS
Institutional Trust, MFS Variable Insurance Trust, MFS Municipal Income Trust,
MFS Government Markets Income Trust, MFS Multimarket Income Trust, MFS
Intermediate Income Trust, MFS Charter Income Trust, MFS Special Value Trust,
and seven variable accounts, each of which is a registered investment company
established by Sun Life Assurance Company of Canada (U.S.), a subsidiary of Sun
Life Assurance Company of Canada ("Sun Life") in connection with the sale of
various fixed/variable annuity contracts. MFS and its wholly owned subsidiary,
MFS Institutional Advisors, Inc., also provide investment advice to substantial
private clients.
    
 
   
MFS is America's oldest mutual fund organization. MFS and its predecessor
organizations have a history of money management dating from 1924 and the
founding of the first mutual fund in the United States, Massachusetts Investors
Trust. Net assets under the management of the MFS organization were
approximately $83.1 billion on behalf of approximately 3.5 million investor
accounts as of September 30, 1998. As of such date, the MFS organization managed
approximately $54.6 billion in assets in equity securities and $20.6 billion of
assets in fixed income securities. Approximately $4.3 billion of assets managed
by MFS are invested in securities of foreign issuers and non-U.S. dollar
denominated securities of U.S. issuers. MFS is a subsidiary of Sun Life
Assurance Company of Canada (U.S.) Financial Services Holdings, Inc. ("Sun Life
of Canada (U.S.)") which in turn is an indirect wholly owned subsidiary of Sun
Life Assurance Company of Canada ("Sun Life"). The Directors of MFS are John W.
Ballen, Thomas J. Cashman, Joseph Dello Russo, John D. McNeil, Kevin R. Parke,
Arnold D. Scott, William W. Scott, Jr., Jeffrey L. Shames and Donald A. Stewart.
Mr. Shames is the Chairman and Chief Executive Officer of MFS. Mr. Ballen is the
President and the Chief Investment Officer of MFS. Mr. Cashman is an Executive
Vice President of MFS. Mr. W. Dello Russo is the Chief Financial Officer and an
Executive Vice President of MFS. Mr. Parke is the Chief Equity Officer, Director
of Equity Research and an Executive Vice President of MFS. Mr. Arnold Scott is
the Secretary and a Senior Executive Vice President of MFS and Mr. William Scott
is the President of MFS Fund Distributors, Inc., the distributor of MFS Funds.
Messrs. McNeil and Stewart are the Chairman and the President, respectively, of
Sun Life. Sun Life, a mutual life insurance company, is one of the largest
international life insurance companies and has been operating in the U.S. since
1895, establishing a headquarters office here in 1973. The executive officers of
MFS report to the Chairman of Sun Life.
    
 
   
Mr. Shames, the Chairman of MFS, is a Trustee of the Trust. W. Thomas London,
Stephen E. Cavan, James O. Yost, Ellen Moynihan, Mark E. Bradley and James R.
Bordewick, Jr., all of whom are officers of MFS, are officers of the Trust.
    
 
                                       19
<PAGE>   139
 
In certain instances there may be securities which are suitable for the Fund's
portfolios as well as for portfolios of other clients of MFS. Some simultaneous
transactions are inevitable when several clients receive investment advice from
MFS, particularly when the same security is suitable for more than one client.
While in some cases this arrangement could have a detrimental effect on the
price or availability of the security as far as the Fund is concerned, in other
cases, however, it may produce increased investment opportunities for the Fund.
 
ADMINISTRATOR -- MFS provides the Fund with certain financial, legal,
compliance, shareholder communications and other administrative services
pursuant to a Master Administrative Services Agreement dated March 1, 1997, as
amended. Under this Agreement, the Fund pays MFS an administrative fee up to
0.015% per annum of the Fund's average daily net assets. This fee reimburses MFS
for a portion of the costs it incurs to provide such services.
 
DISTRIBUTOR -- MFD, a wholly owned subsidiary of MFS, is the distributor of
shares of the Fund and also serves as distributor for each of the other MFS
Funds.
 
SHAREHOLDER SERVICING AGENT -- MFS Service Center, Inc. (the "Shareholder
Servicing Agent"), a wholly owned subsidiary of MFS, performs transfer agency
and certain other services for the Fund.
 
   
8.  YEAR 2000 ISSUES
    
 
   
The Fund could be adversely affected if the computer systems used by MFS, the
Fund's other service providers or the companies in which the Fund invests do not
properly process date-related information from and after January 1, 2000 (the
"Year 2000 Issue"). MFS recognizes the importance of the Year 2000 Issue and, to
address Year 2000 compliance, created a Year 2000 Program Management Office in
1996, which is separately funded, has a specialized staff and reports directly
to MFS senior management. The Office, with the help of external consultants, is
responsible for ascertaining that all internal systems, data feeds and third
party applications are Year 2000 compliant. While MFS is confident that all MFS
systems will be Year 2000 compliant before the turn of the century, there are
significant systems interdependencies in the domestic and foreign markets for
securities, the business environments in which companies held by the Fund
operate and in MFS' own business environment. MFS has been actively working with
the Fund's other service providers to identify and respond to potential problems
in an effort to ensure Year 2000 compliance or develop contingency plans. Year
2000 compliance is also one of the factors considered by MFS in its ongoing
assessment of companies in which the Fund invests. There can be no assurance,
however, that these steps will be sufficient to avoid any adverse impact on the
Fund.
    
 
   
9.  INFORMATION CONCERNING SHARES OF THE FUND
    
 
PURCHASES
 
Class A, B and C shares of the Fund may be purchased at the public offering
price through any dealer. As used in the Prospectus and any appendices thereto
the term "dealer" includes any broker, dealer, bank (including bank trust
departments), registered investment adviser, financial planner and any other
financial institutions having a selling agreement or other similar agreement
with MFD. Dealers may also charge their customers fees relating to investment in
the Fund.
 
                                       20
<PAGE>   140
 
This Prospectus offers Class A, B and C shares, which bear sales charges and
distribution fees in different forms and amounts, as described below:
 
CLASS A SHARES:  Class A shares are generally offered at net asset value plus an
initial sales charge, but in certain cases are offered at net asset value
without an initial sales charge but subject to a CDSC.
 
PURCHASES SUBJECT TO INITIAL SALES CHARGE.  Class A shares are offered at net
asset value plus an initial sales charge as follows:
- --------------------------------------------------------------------------------
 
<TABLE>
<CAPTION>
                                              SALES CHARGE* AS           DEALER
                                               PERCENTAGE OF:        ALLOWANCE AS A
                                           OFFERING    NET AMOUNT    PERCENTAGE OF
           AMOUNT OF PURCHASE               PRICE       INVESTED     OFFERING PRICE
- -----------------------------------------------------------------------------------
<S>                                        <C>         <C>           <C>
Less than $50,000........................   5.75%        6.10%           5.00%
$50,000 but less than $100,000...........    4.75         4.99            4.00
$100,000 but less than $250,000..........    4.00         4.17            3.20
$250,000 but less than $500,000..........    2.95         3.04            2.25
$500,000 but less than $1,000,000........    2.20         2.25            1.70
$1,000,000 or more.......................   None**       None**       See Below**
- -----------------------------------------------------------------------------------
</TABLE>
 
 *Because of rounding in the calculation of offering price, actual sales charges
  may be more or less than those calculated using the percentages above.
**A CDSC will apply to such purchases, as discussed below.
 
MFD allows discounts to dealers (which are alike for all dealers) from the
applicable public offering price as shown in the above table. In the case of the
maximum sales charge, the dealer retains 5% and MFD retains approximately 3/4 of
1% of the public offering price. The sales charge may vary depending on the
number of shares of the Fund as well as certain other MFS Funds owned or being
purchased, the existence of an agreement to purchase additional shares during a
13-month period (or 36-month period for purchases of $1 million or more) or
other special purchase programs. A description of the Right of Accumulation,
Letter of Intent and Group Purchase privileges by which the sales charge may be
reduced is set forth in the SAI.
 
PURCHASES SUBJECT TO A CDSC (but not an initial sales charge). In the following
five circumstances, Class A shares are offered at net asset value without an
initial sales charge, but subject to a CDSC equal to 1% of the lesser of the
value of the shares redeemed (exclusive of reinvested dividend and capital gain
distributions) or the total cost of such shares, in the event of a share
redemption within 12 months following the purchase:
 
         (i) on investments of $1 million or more in Class A shares:
 
   
         (ii) on investments in Class A shares by certain retirement plans
    subject to the Employee Retirement Income Security Act of 1974, as amended
    ("ERISA"), if, prior to July 1, 1996: (a) the plan had established an
    account with the Shareholder Servicing Agent and (b) the sponsoring
    organization had demonstrated to the satisfaction of MFD that either (i) the
    employer had at least 25 employees or (ii) the aggregate purchases by the
    retirement plan of Class A shares of Funds in the MFS Funds would be in an
    aggregate amount of at least $250,000 within a reasonable period of time, as
    determined by MFD in its sole discretion;
    
 
                                       21
<PAGE>   141
 
   
        (iii) on investments in Class A shares by certain retirement plans
    subject to ERISA, if: (a) the retirement plan and/or sponsoring organization
    subscribes to the MFS FUNDamental 401(k) Program or any similar
    recordkeeping system made available by the Shareholder Servicing Agent (the
    "MFS Participant Recordkeeping System"); (b) the plan establishes an account
    with the Shareholder Servicing Agent on or after July 1, 1996; (c) the
    aggregate purchases by the retirement plan of Class A shares of the MFS
    Funds will be in an aggregate amount of at least $500,000 within a
    reasonable period of time, as determined by MFD in its sole discretion; and
    (d) the plan has not redeemed its Class B shares in the MFS Funds in order
    to purchase Class A shares under this category;
    
 
   
        (iv) on investments in Class A shares by certain retirement plans
    subject to ERISA, if: (a) the plan establishes an account with the
    Shareholder Servicing Agent on or after July 1, 1996 and (b) the plan has,
    at the time of purchase, a market value of $500,000 or more invested in
    shares of any class or classes of the MFS Funds; THE RETIREMENT PLAN WILL
    QUALIFY UNDER THIS CATEGORY ONLY IF THE PLAN OR ITS SPONSORING ORGANIZATION
    INFORMS THE SHAREHOLDER SERVICING AGENT PRIOR TO THE PURCHASE THAT THE PLAN
    HAS A MARKET VALUE OF $500,000 OR MORE INVESTED IN SHARES OF ANY CLASS OR
    CLASSES OF THE MFS FUNDS; THE SHAREHOLDER SERVICING AGENT HAS NO OBLIGATION
    INDEPENDENTLY TO DETERMINE WHETHER SUCH A PLAN QUALIFIES UNDER THIS
    CATEGORY; and
    
 
         (v) on investments in Class A shares by certain retirement plans
    subject to ERISA if: (a) the plan establishes an account with the
    Shareholder Servicing Agent on or after July 1, 1997; (b) such plan's
    records are maintained on a pooled basis by the Shareholder Servicing Agent;
    and (c) the sponsoring organization demonstrates to the satisfaction of MFD
    that, at the time of purchase the employer has at least 200 eligible
    employees and the plan has aggregate assets of at least $2,000,000.
 
In the case of all such purchases, MFD will pay commissions to dealers on new
investments in Class A shares made through such dealers as follows:
 
<TABLE>
<CAPTION>
COMMISSION PAID BY MFD TO DEALERS        CUMULATIVE PURCHASE AMOUNT
- ---------------------------------   ------------------------------------
<C>                                 <S>
              1.00%                 On the first $2,000,000, plus
              0.80%                 Over $2,000,000 to $3,000,000, plus
              0.50%                 Over $3,000,000 to $50,000,000, plus
              0.25%                 Over $50,000,000
</TABLE>
 
   
For purposes of determining the level of commissions to be paid to dealers with
respect to a shareholder's new investment in Class A, purchases for each
shareholder account (and certain other accounts for which the shareholder is a
record or beneficial holder) will be aggregated over a 12-month period
(commencing from the date of the first such purchases).
    
 
See "Redemptions and Repurchases -- Contingent Deferred Sales Charge" in the
Prospectus for further discussion of the CDSC.
 
WAIVERS OF INITIAL SALES CHARGE AND CDSC. In certain circumstances, the initial
sales charge imposed upon purchases of Class A shares and the CDSC imposed upon
redemption of Class A shares is waived. These circumstances are described in
Appendix A to this Prospectus. In addition to these circumstances, the CDSC
imposed upon the redemption of Class A shares is
 
                                       22
<PAGE>   142
 
waived with respect to shares held by certain retirement plans qualified under
Section 401(a) or 403(b) of the Code, and subject to ERISA, where:
 
         (i) the retirement plan and/or sponsoring organization does not
    subscribe to the MFS Participant Recordkeeping System; and
 
        (ii) the retirement plan and/or sponsoring organization demonstrates to
    the satisfaction of, and certifies to, the Shareholder Servicing Agent that
    the retirement plan has, at the time of certification or will have pursuant
    to a purchase order placed with the certification, a market value of
    $500,000 or more invested in shares of any class or classes of the MFS Funds
    and aggregate assets of at least $10 million;
 
provided, however, that the CDSC will not be waived (i.e., it will be imposed)
(a) with respect to plans which establish an account with the Shareholder
Servicing Agent on or after November 1, 1997, in the event that the plan makes a
complete redemption of all of its shares in the MFS Funds, or (b) with respect
to plans which established an account with the Shareholder Servicing Agent prior
to November 1, 1997, in the event that there is a change in law or regulations
which results in a material adverse change to the tax advantaged nature of the
plan, or in the event that the plan and/or sponsoring organization: (i) becomes
insolvent or bankrupt; (ii) is terminated under ERISA or is liquidated or
dissolved; or (iii) is acquired by, merged into, or consolidated with, any other
entity.
 
CLASS B SHARES:  Class B shares are offered at net asset value without an
initial sales charge but subject to a CDSC upon redemption as follows:
 
<TABLE>
<CAPTION>
          YEAR OF                  CONTINGENT
        REDEMPTION               DEFERRED SALES
      AFTER PURCHASE                 CHARGE
      --------------             --------------
<S>                              <C>
First......................            4%
Second.....................            4%
Third......................            3%
Fourth.....................            3%
Fifth......................            2%
Sixth......................            1%
Seventh and following......            0%
</TABLE>
 
The CDSC imposed is assessed against the lesser of the value of the shares
redeemed (exclusive of reinvested dividends and capital gain distributions) or
the total cost of such shares. No CDSC is assessed against shares acquired
through the automatic reinvestment of dividends or capital gain distributions.
 
Except as described below, MFD will pay commissions to dealers of 3.75% of the
purchase price of Class B shares purchased through dealers. MFD will also
advance to dealers the first year service fee payable under the Fund's
Distribution Plan (see "Distribution Plan" below) at a rate equal to 0.25% of
the purchase price of such shares. Therefore, the total amount paid to a dealer
upon the sale of Class B shares is 4% of the purchase price of the shares
(commission rate of 3.75% plus a service fee equal to 0.25% of the purchase
price).
 
   
Class B shares purchased by a retirement plan whose sponsoring organization
subscribes to the MFS Participant Recordkeeping System and which has established
its account with the Shareholder Servicing Agent between July 1, 1996 and
December 31, 1998, will be subject to the CDSC described above, only under
limited circumstances, as explained below under "Waivers of
    
                                       23
<PAGE>   143
 
CDSC." With respect to such purchases, MFD pays an amount to dealers equal to
3.00% of the amount purchased through such dealers (rather than the 4.00%
payment described above), which is comprised of a commission of 2.75% plus the
advancement of the first year service fee equal to 0.25% of the purchase price
payable under the Fund's Distribution Plan.
 
   
For purchases of Class B shares by a retirement plan whose sponsoring
organization subscribes to the MFS Recordkeeper Plus product and which
establishes its account with MFSC on or after January 1, 1999 (provided that the
plan establishment paperwork is received by MFSC in good order on or after
November 15, 1998), MFD pays no up front commissions to dealers, but instead
pays an amount to dealers equal to 1% per annum of the average daily net assets
of the Fund attributable to plan assets, payable at the rate of 0.25% at the end
of each calendar quarter, in arrears. This commission structure is not available
with respect to a plan with a pre-existing account(s) with any MFS Fund which
seeks to switch to the MFS Recordkeeper Plus Product.
    
 
   
Certain retirement plans are eligible to purchase Class A shares of the Fund at
net asset value without an initial sales charge but subject to a 1% CDSC if the
plan has, at the time of purchase, a market value of $500,000 or more invested
in shares of any class or classes of the MFS Funds. IN THIS EVENT, THE PLAN OR
ITS SPONSORING ORGANIZATION SHOULD INFORM THE SHAREHOLDER SERVICING AGENT THAT
THE PLAN IS ELIGIBLE TO PURCHASE CLASS A SHARES UNDER THIS CATEGORY; THE
SHAREHOLDER SERVICING AGENT HAS NO OBLIGATION INDEPENDENTLY TO DETERMINE WHETHER
SUCH A PLAN QUALIFIES UNDER THIS CATEGORY FOR THE PURCHASE OF CLASS A SHARES.
    
 
See "Redemptions and Repurchases -- Contingent Deferred Sales Charge" for
further discussion of the CDSC.
 
   
WAIVERS OF CDSC.  In certain circumstances, the CDSC imposed upon redemption of
Class B shares is waived. These circumstances are described in Appendix A to
this Prospectus. In addition to these circumstances, the CDSC imposed upon the
redemption of Class B shares is waived with respect to shares held by a
retirement plan whose sponsoring organization subscribes to the MFS Participant
Recordkeeping System and which established an account with the Shareholder
Servicing Agent between July 1, 1996 and December 31, 1998; provided, however,
that the CDSC will not be waived (i.e., it will be imposed) in the event that
there is a change in law or regulations which results in a material adverse
change to the tax advantaged nature of the plan, or in the event that the plan
and/or sponsoring organization: (i) becomes insolvent or bankrupt; (ii) is
terminated under ERISA or is liquidated or dissolved; or (iii) is acquired by,
merged into, or consolidated with, and other entity.
    
 
   
In addition to these circumstances, the CDSC imposed upon the redemption of
Class B shares is waived with respect to shares held by a retirement plan whose
sponsoring organization subscribes to the MFS Recordkeeper Plus product and
which establishes its account with MFSC on or after January 1, 1999 (provided
that the plan establishment paperwork is received by MFSC in good order on or
after November 15, 1998). A plan with a pre-existing account(s) with any MFS
Fund which switches to the MFS Recordkeeper Plus product will not become
eligible for this waiver category.
    
 
CONVERSION OF CLASS B SHARES.  Class B shares of the Fund that remain
outstanding for approximately eight years will convert to Class A shares of the
same Fund. Shares purchased through the reinvestment of distributions paid in
respect of Class B shares will be treated as Class B shares for purposes of the
payment of the distribution and service fees under the Fund's
                                       24
<PAGE>   144
 
Distribution Plan. See "Distribution Plan" below. However, for purposes of
conversion to Class A shares, all shares in a shareholder's account that were
purchased through the reinvestment of dividends and distributions paid in
respect of Class B shares (and which have not converted to Class A shares as
provided in the following sentence) will be held in a separate sub-account. Each
time any Class B shares in the shareholder's account (other than those in the
sub-account) convert to Class A shares, a portion of the Class B shares then in
the sub-account will also convert to Class A shares. The portion will be
determined by the ratio that the shareholder's Class B shares not acquired
through reinvestment of dividends and distributions that are converting to Class
A shares bear to the shareholder's total Class B shares not acquired through
reinvestment. The conversion of Class B shares to Class A shares is subject to
the continuing availability of a ruling from the Internal Revenue Service or an
opinion of counsel that such conversion will not constitute a taxable event for
federal tax purposes. There can be no assurance that such ruling or opinion will
be available, and the conversion of Class B shares to Class A shares will not
occur if such ruling or opinion is not available. In such event, Class B shares
would continue to be subject to higher expenses than Class A shares for an
indefinite period.
 
CLASS C SHARES:  Class C shares are offered at net asset value without an
initial sales charge but are subject to a CDSC upon redemption of 1.00% during
the first year. Class C shares do not convert to any other class of the Fund.
The maximum investment in Class C shares that may be made is up to $1,000,000
per transaction.
 
The CDSC imposed is assessed against the lesser of the value of the shares
redeemed (exclusive of reinvested dividend and capital gain distributions) or
the total cost of such shares. No CDSC is assessed against shares acquired
through the automatic reinvestment of dividend or capital gain distributions.
See "Redemptions and Repurchases -- Contingent Deferred Sales Charge" below for
further discussion of the CDSC.
 
MFD will pay dealers 1.00% of the purchase price of Class C shares purchased
through dealers and, as compensation therefor, MFD will retain the 1.00% per
annum distribution and service fee paid under the Fund's Distribution Plan to
MFD for the first year after purchase (see "Distribution Plan" below).
 
Class C shares are not currently available for purchase by any retirement plan
qualified under Sections 401(a) or 403(b) of the Code if the retirement plan
and/or the sponsoring organization subscribe to the MFS FUNDamental 401(k) Plan
or another similar recordkeeping program made available by the Shareholder
Servicing Agent.
 
WAIVERS OF CDSC.  In certain circumstances, the CDSC imposed upon redemption of
Class C shares is waived. These circumstances are described in Appendix A to
this Prospectus.
 
GENERAL:  The following information applies to purchases of all classes of the
Fund's shares.
 
MINIMUM INVESTMENT.  Except as described below, the minimum initial investment
is $1,000 per account and the minimum additional investment is $50 per account.
Accounts being established for monthly automatic investments and under payroll
savings programs and tax-deferred retirement programs (other than IRA's)
involving the submission of investments by means of group remittal statements
are subject to a $50 minimum on initial and additional investments per account.
The minimum initial investment for IRAs is $250 per account and the
 
                                       25
<PAGE>   145
 
minimum additional investment is $50 per account. Accounts being established for
participation in the Automatic Exchange Plan are subject to a $50 minimum on
initial and additional investments per account. There are also other limited
exceptions to these minimums for certain tax-deferred retirement programs. Any
minimums may be changed at any time at the discretion of MFD. The Fund reserves
the right to cease offering its shares for sale at any time.
 
SUBSEQUENT INVESTMENT BY TELEPHONE:  Each shareholder may purchase additional
shares of any MFS Fund by telephoning the Shareholder Servicing Agent toll-free
at (800) 225-2606. The minimum purchase amount is $50 and the maximum purchase
amount is $100,000. Shareholders wishing to avail themselves of this telephone
purchase privilege must so elect on their Account Application and designate
thereon a bank and account number from which purchases will be made. If a
telephone purchase request is received by the Shareholder Servicing Agent on any
business day prior to the close of regular trading on the Exchange (generally,
4:00 p.m., Eastern time), the purchase will occur at the closing net asset value
of the shares purchased on that day. The Shareholder Servicing Agent may be
liable for any losses resulting from unauthorized telephone transactions if it
does not follow reasonable procedures designed to verify the identity of the
caller. The Shareholder Servicing Agent will request personal or other
information from the caller, and will normally also record calls. Shareholders
should verify the accuracy of confirmation statements immediately after their
receipt.
 
   
RIGHT TO REJECT PURCHASE ORDERS/MARKET TIMING.  Purchases and exchanges should
be made for investment purposes only. The Fund and MFD each reserve the right to
reject or restrict any specific purchase or exchange request. Because an
exchange request involves both a request to redeem shares of one fund and to
purchase shares of another fund, the Fund considers the underlying redemption
request conditioned upon the acceptance of the underlying purchase request.
Therefore, in the event that the Fund or MFD rejects an exchange request,
neither the redemption nor the purchase side of the exchange will be processed.
    
 
   
The MFS Family of Funds is not designed for professional market timing
organizations or other entities using programmed or frequent exchanges. The MFS
Family of Funds defines a "market timer" as an individual or organization acting
on behalf of one or more individuals, if (i) the individual or organization
makes six or more exchange requests among the MFS Family of Funds or three or
more exchange requests out of any of the MFS high yield bond funds or MFS
municipal bond funds per calendar year and (ii) any one of such exchange
requests represents shares equal in value to $1 million or more. Accounts under
common ownership or control, including accounts administered by market timers,
will be aggregated for purposes of this definition.
    
 
   
As noted above, the Fund and MFD each reserves the right to reject or restrict
any specific purchase and exchange request and, in addition, may impose specific
limitations with respect to market timers, including (i) delaying for up to
seven days the purchase side of an exchange request by market timers, (ii)
rejecting or otherwise restricting purchase or exchange requests by market
timers; and (iii) permitting exchanges by market timers only into certain MFS
Funds.
    
 
DEALER CONCESSIONS.  Dealers may receive different compensation with respect to
sales of Class A, Class B and Class C shares. In addition, from time to time,
MFD may pay dealers 100% of the applicable sales charge on sales of Class A
shares of certain specified MFS Funds sold by such dealer during a specified
sales period. In addition, MFD or its affiliates may, from time to
 
                                       26
<PAGE>   146
 
time, pay dealers an additional commission equal to 0.50% of the net asset value
of all of the Class B and/or Class C shares of certain specified MFS Funds sold
by such dealer during a specified sales period. In addition, from time to time,
MFD, at its expense, may provide additional commissions, compensation or
promotional incentives ("concessions") to dealers which sell or arrange for the
sale of shares of the Fund. Such concessions provided by MFD may include
financial assistance to dealers in connection with preapproved conferences or
seminars, sales or training programs for invited registered representatives and
other employees, payment for travel expenses, including lodging, incurred by
registered representatives and other employees for such seminars or training
programs, seminars for the public, advertising and sales campaigns regarding one
or more MFS Fund, and/or other dealer-sponsored events. From time to time, MFD
may make expense reimbursements for special training of a dealer's registered
representatives and other employees in group meetings or to help pay the
expenses of sales contests. Other concessions may be offered to the extent not
prohibited by state laws or any self-regulatory agency, such as the NASD.
 
SPECIAL INVESTMENT PROGRAMS.  For shareholders who elect to participate in
certain investment programs (e.g., the Automatic Investment Plan) or other
shareholder services, MFD or its affiliates may either (i) give a gift of
nominal value, such as a hand-held calculator or (ii) make a nominal charitable
contribution on their behalf.
 
RESTRICTIONS ON ACTIVITIES OF NATIONAL BANKS.  The Glass-Steagall Act prohibits
national banks from engaging in the business of underwriting, selling or
distributing securities. Although the scope of the prohibition has not been
clearly defined, MFD believes that such Act should not preclude banks from
entering into agency agreements with MFD. If, however, a bank were prohibited
from so acting, the Trustees would consider what actions, if any, would be
necessary to continue to provide efficient and effective shareholder services in
respect of shareholders who invested in the Fund through a national bank. It is
not expected that shareholders would suffer any adverse financial consequence as
a result of these occurrences. In addition, state securities laws on this issue
may differ from the interpretation of federal law expressed herein and banks and
financial institutions may be required to register as broker-dealers pursuant to
state law.
                            ------------------------
 
A shareholder whose shares are held in the name of, or controlled by, a dealer
might not receive many of the privileges and services from the Fund (such as
Right of Accumulation, Letter of Intent and certain recordkeeping services) that
the Fund ordinarily provides.
 
EXCHANGES
 
Subject to the requirements set forth below, some or all of the shares in an
account with the Fund for which payment has been received by the Fund (i.e., an
established account) may be exchanged for shares of the same class of any of the
other MFS Funds at net asset value (if available for sale). Shares of one class
may not be exchanged for shares of any other class.
 
EXCHANGES AMONG MFS FUNDS (EXCLUDING EXCHANGES FROM MFS MONEY MARKET FUNDS):  No
initial sales charges or CDSC will be imposed in connection with an exchange
from shares of an MFS Fund to shares of any other MFS Fund, except with respect
to exchanges from an MFS money market fund to another MFS Fund which is not an
MFS money market fund (discussed below). With respect to an exchange involving
shares subject to a CDSC, the CDSC will be
 
                                       27
<PAGE>   147
 
unaffected by the exchange and the holding period for purposes of calculating
the CDSC will carry over to the acquired shares.
 
EXCHANGES FROM AN MFS MONEY MARKET FUND:  Special rules apply with respect to
the imposition of an initial sales charge or a CDSC for exchanges from an MFS
money market fund to another MFS Fund which is not an MFS money market fund.
These rules are described under the caption "Exchanges" in the Prospectuses of
those MFS money market funds.
 
EXCHANGES INVOLVING THE MFS FIXED FUND:  Class A shares of any MFS Fund held by
certain qualified retirement plans may be exchanged for units of participation
of the MFS Fixed Fund (a bank collective investment fund) (the "Units"), and
Units may be exchanged for Class A shares of any MFS Fund. With respect to
exchanges between Class A shares subject to a CDSC and Units, the CDSC will
carry over to the acquired shares or Units and will be deducted from the
redemption proceeds when such shares or Units are subsequently redeemed,
assuming the CDSC is then payable (the period during which the Class A shares
and the Units were held will be aggregated for purposes of calculating the
applicable CDSC). In the event that a shareholder initially purchases Units and
then exchanges into Class A shares subject to an initial sales charge of an MFS
Fund, the initial sales charge shall be due upon such exchange, but will not be
imposed with respect to any subsequent exchanges between such Class A shares and
Units with respect to shares on which the initial sales charge has already been
paid. In the event that a shareholder initially purchases Units and then
exchanges into Class A shares subject to a CDSC of an MFS Fund, the CDSC period
will commence upon such exchange, and the applicability of the CDSC with respect
to subsequent exchanges shall be governed by the rules set forth above in this
paragraph.
 
GENERAL:  A shareholder should read the prospectus of the other MFS Fund into
which an exchange is made and consider the differences in objectives, policies
and restrictions before making any exchange. Exchanges will be made only after
instructions in writing or by telephone (an "Exchange Request") are received for
an established account by the Shareholder Servicing Agent in proper form (i.e.,
if in writing -- signed by the record owner(s) exactly as the shares are
registered; if by telephone -- proper account identification is given by the
dealer or shareholder of record) and each exchange must involve either shares
having an aggregate value of at least $1,000 ($50 in case of retirement plan
participants whose sponsoring organizations subscribe to the MFS FUNDamental
401(k) Plan or another similar 401(k) recordkeeping system made available by the
Shareholder Servicing Agent) or all the shares in the account. If an Exchange
Request is received by the Shareholder Servicing Agent on any business day prior
to the close of regular trading on the Exchange (generally, 4:00 p.m., Eastern
time), the exchange will occur on that day if all the requirements set forth
above have been complied with at that time and subject to the Fund's right to
reject purchase orders. No more than five exchanges may be made in any one
Exchange Request by telephone. Additional information concerning this exchange
privilege and prospectuses for any of the other MFS Funds may be obtained from
dealers or the Shareholder Servicing Agent. For federal and (generally) state
income tax purposes, an exchange is treated as a sale of the shares exchanged
and, therefore, an exchange could result in a gain or loss to the shareholder
making the exchange. Exchanges by telephone are automatically available to most
non-retirement plan accounts and certain retirement plan accounts. For further
information regarding exchanges by telephone, see "Redemptions by
 
                                       28
<PAGE>   148
 
Telephone." The exchange privilege (or any aspect of it) may be changed or
discontinued and is subject to certain limitations, including certain
restrictions on purchases by market timers.
 
REDEMPTIONS AND REPURCHASES
 
A shareholder may withdraw all or any portion of the value of his account on any
date on which the Fund is open for business by redeeming shares at their net
asset value (a redemption ) or by selling such shares to the Fund through a
dealer (a repurchase). Certain redemptions and repurchases are, however, subject
to a CDSC. See "Contingent Deferred Sales Charge" below. Because the net asset
value of shares of the account fluctuates, redemptions or repurchases, which are
taxable transactions, are likely to result in gains or losses to the
shareholder. When a shareholder withdraws an amount from his account, the
shareholder is deemed to have tendered for redemption a sufficient number of
full and fractional shares in his account to cover the amount withdrawn. The
proceeds of a redemption or repurchase will normally be available within seven
days, except for shares purchased or received in exchange for shares purchased
by check (including certified checks or cashier's checks). Payment of redemption
proceeds may be delayed for up to 15 days from the purchase date in an effort to
assure that such check has cleared.
 
REDEMPTION BY MAIL:  Each shareholder may redeem all or any portion of the
shares in his account by mailing or delivering to the Shareholder Servicing
Agent (see back cover for address) a stock power with a written request for
redemption or letter of instruction, together with his share certificates (if
any were issued), all in "good order" for transfer. "Good order" generally means
that the stock power, written request for redemption, letter of instruction or
certificate must be endorsed by the record owner(s) exactly as the shares are
registered and the signature(s) must be guaranteed in the manner set forth below
under the caption "Signature Guarantee." In addition, in some cases "good order"
will require the furnishing of additional documents. The Shareholder Servicing
Agent may make certain de minimis exceptions to the above requirements for
redemption. Within seven days after receipt of a redemption request in "good
order" by the Shareholder Servicing Agent, the Fund will make payment in cash of
the net asset value of the shares next determined after such redemption request
was received, reduced by the amount of any applicable CDSC described above and
the amount of any income tax required to be withheld, except during any period
in which the right of redemption is suspended or date of payment is postponed
because the Exchange is closed or trading on such Exchange is restricted or to
the extent otherwise permitted by the 1940 Act if an emergency exists. See "Tax
Status" below.
 
REDEMPTION BY TELEPHONE:  Each shareholder may redeem an amount from his account
by telephoning the Shareholder Servicing Agent toll-free at (800) 225-2606.
Shareholders wishing to avail themselves of this telephone redemption privilege
must so elect on their Account Application, designate thereon a bank and account
number to receive the proceeds of such redemption, and sign the Account
Application Form with the signature(s) guaranteed in the manner set forth below
under the caption "Signature Guarantee." The proceeds of such a redemption,
reduced by the amount of any applicable CDSC and the amount of any income tax
required to be withheld, are mailed by check to the designated account, without
charge, if the redemption proceeds do not exceed $1,000, and are wired in
federal funds to the designated account if the redemption proceeds exceed
$1,000. If a telephone redemption request is received
 
                                       29
<PAGE>   149
 
by the Shareholder Servicing Agent by the close of regular trading on the
Exchange on any business day, shares will be redeemed at the closing net asset
value of the Fund on that day. Subject to the conditions described in this
section, proceeds of a redemption are normally mailed or wired on the next
business day following the date of receipt of the order for redemption. The
Shareholder Servicing Agent may be liable for any losses resulting from
unauthorized telephone transactions if it does not follow reasonable procedures
designed to verify the identity of the caller. The Shareholder Servicing Agent
will request personal or other information from the caller, and will normally
also record calls. Shareholders should verify the accuracy of confirmation
statements immediately after their receipt.
 
REPURCHASE THROUGH A DEALER:  If a shareholder desires to sell his shares
through his dealer (a repurchase), the shareholder can place a repurchase order
with his dealer, who may charge the shareholder a fee. IF THE DEALER RECEIVES
THE SHAREHOLDER'S ORDER PRIOR TO THE CLOSE OF REGULAR TRADING ON THE EXCHANGE
AND COMMUNICATES IT TO MFD BEFORE THE CLOSE OF BUSINESS ON THE SAME DAY, THE
SHAREHOLDER WILL RECEIVE THE NET ASSET VALUE CALCULATED ON THAT DAY, REDUCED BY
THE AMOUNT OF ANY APPLICABLE CDSC AND THE AMOUNT OF ANY INCOME TAX REQUIRED TO
BE WITHHELD.
 
CONTINGENT DEFERRED SALES CHARGE:  Investments in Class A, Class B and Class C
shares ("Direct Purchases") will be subject to a CDSC for a period of: (i) with
respect to Class A and Class C shares, 12 months (however, the CDSC on Class A
shares is only imposed with respect to purchases of $1 million or more of Class
A shares or purchases by certain retirement plans of Class A shares); or (ii)
with respect to Class B shares, six years. Purchases of Class A shares made
during a calendar month, regardless of when during the month the investment
occurred, will age one month on the last day of the month and each subsequent
month. Class C shares and Class B shares purchased on or after January 1, 1993
will be aggregated on a calendar month basis -- all transactions made during a
calendar month, regardless of when during the month they have occurred, will age
one year at the close of business on the last day of such month in the following
calendar year and each subsequent year. For Class B shares of the Fund purchased
prior to January 1, 1993, transactions will be aggregated on a calendar year
basis -- all transactions made during a calendar year, regardless of when during
the year they have occurred, will age one year at the close of business on
December 31 of that year and each subsequent year.
 
At the time of a redemption, the amount by which the value of a shareholder's
account for a particular class of shares represented by Direct Purchases exceeds
the sum of the six calendar year aggregations (12 months in the case of
purchases of Class C shares and of purchases of $1 million or more of Class A
shares or purchases by certain retirement plans of Class A shares) of Direct
Purchases may be redeemed without charge ("Free Amount"). Moreover, no CDSC is
ever assessed on additional shares acquired through the automatic reinvestment
of dividends or capital gain distributions ("Reinvested Shares"). Therefore, at
the time of redemption of a particular class, (i) any Free Amount is not subject
to the CDSC, and (ii) the amount of redemption equal to the then-current value
of Reinvested Shares is not subject to the CDSC, but (iii) any amount of the
redemption in excess of the aggregate of the then-current value of Reinvested
Shares and the Free Amount is subject to a CDSC. The CDSC will first be applied
against the amount of Direct Purchases which will result in any such charge
being imposed at the
 
                                       30
<PAGE>   150
 
lowest possible rate. The CDSC to be imposed upon redemptions will be calculated
as set forth in "Purchases" above.
 
The applicability of a CDSC will be unaffected by exchanges or transfers of
registration, except as described in Appendix A hereto.
 
GENERAL:  The following information applies to redemptions and repurchases of
all classes of the Fund's shares.
 
SIGNATURE GUARANTEE.  In order to protect shareholders against fraud, the Fund
requires, in certain instances as indicated above, that the shareholder's
signature be guaranteed. In these cases the shareholder's signature must be
guaranteed by an eligible bank, broker, dealer, credit union, national
securities exchange, registered securities association, clearing agency or
savings association. Signature guarantees shall be accepted in accordance with
policies established by the Shareholder Servicing Agent.
 
REINSTATEMENT PRIVILEGE.  Shareholders of the Fund who have redeemed their
shares have a one-time right to reinvest the redemption proceeds in the same
class of shares of any of the MFS Funds (if shares of such Fund are available
for sale) at net asset value (with a credit for any CDSC paid) within 90 days of
the redemption pursuant to the Reinstatement Privilege. If the shares credited
for any CDSC paid are then redeemed within six years of the initial purchase in
the case of Class B shares or within 12 months of the initial purchase for Class
C shares and certain Class A share purchases, a CDSC will be imposed upon
redemption. Such purchases under the Reinstatement Privilege are subject to all
limitations in the SAI regarding this privilege.
 
IN-KIND DISTRIBUTIONS.  The Trust agrees to redeem shares of the Fund solely in
cash up to the lesser of $250,000 or 1% of the net asset value of the Fund
during any 90-day period for any one shareholder. The Fund has reserved the
right to pay other redemptions, either totally or partially, by a distribution
in-kind of securities (instead of cash) from the Fund's portfolio. The
securities distributed in such a distribution would be valued at the same amount
as that assigned to them in calculating the net asset value for the shares being
sold. If a shareholder received a distribution in-kind, the shareholder could
incur brokerage or transaction charges when converting the securities to cash.
 
INVOLUNTARY REDEMPTIONS/SMALL ACCOUNTS.  Due to the relatively high cost of
maintaining small accounts, the Fund reserves the right to redeem shares in any
account for their then-current value if at any time the total investment in such
account drops below $500 because of redemptions or exchanges, except in the case
of accounts being established for monthly automatic investments and certain
payroll savings programs, Automatic Exchange Plan accounts and tax-deferred
retirement plans, for which there is a lower minimum investment requirement. See
"Purchases -- General -- Minimum Investment." Shareholders will be notified that
the value of their account is less than the minimum investment requirement and
allowed 60 days to make an additional investment before the redemption is
processed.
 
DISTRIBUTION PLAN
 
The Trustees have adopted a Distribution Plan for Class A, Class B and Class C
shares pursuant to Section 12(b) of the 1940 Act and Rule 12b-1 thereunder (the
"Distribution Plan"), after having concluded that there is a reasonable
likelihood that the Plan would benefit the Fund and its shareholders.
 
                                       31
<PAGE>   151
 
In certain circumstances, the fees described below may not be imposed or are
being waived. These circumstances, if any, are described below under the heading
"Current Level of Distribution and Service Fees."
 
FEATURES COMMON TO EACH CLASS OF SHARES:  There are features of the Distribution
Plan that are common to each class of shares, as described below.
 
SERVICE FEES.  The Distribution Plan provides that the Fund may pay MFD a
service fee of up to 0.25% of the average daily net assets attributable to the
class of shares to which the Distribution Plan relates (i.e., Class A shares,
Class B shares or Class C shares, as appropriate) (the "Designated Class")
annually in order that MFD may pay expenses on behalf of the Fund relating to
the servicing of shares of the Designated Class. The service fee is used by MFD
to compensate dealers which enter into a sales agreement with MFD in
consideration for all personal services and/or account maintenance services
rendered by the dealer with respect to shares of the Designated Class owned by
investors for whom such dealer is the dealer or holder of record. MFD may from
time to time reduce the amount of the service fees paid for shares sold prior to
a certain date. Service fees may be reduced for a dealer that is the holder or
dealer of record for an investor who owns shares of the Fund having an aggregate
net asset value at or above a certain dollar level. Dealers may from time to
time be required to meet certain criteria in order to receive service fees. MFD
or its affiliates are entitled to retain all service fees payable under the
Distribution Plan for which there is no dealer of record or for which
qualification standards have not been met as partial consideration for personal
services and/or account maintenance services performed by MFD or its affiliates
to shareholder accounts.
 
DISTRIBUTION FEES.  The Distribution Plan provides that the Fund may pay MFD a
distribution fee based on the average daily net assets attributable to the
Designated Class as partial consideration for distribution services performed
and expenses incurred in the performance of MFD's obligations under its
distribution agreement with the Fund. See "Management of the Fund --
Distributor" in the SAI. The amount of the distribution fee paid by the Fund
with respect to each class differs under the Distribution Plan, as does the use
of MFD of such distribution fees. Such amounts and uses are described below in
the discussion of the provisions of the Distribution Plan relating to each class
of shares. While the amount of compensation received by MFD in the form of
distribution fees during any year may be more or less than the expense incurred
by MFD under its distribution agreement with the Fund, the Fund is not liable to
MFD for any losses MFD may incur in performing services under its distribution
agreement with the Fund.
 
OTHER COMMON FEATURES.  Fees payable under the Distribution Plan are charged to,
and therefore reduce, income allocated to shares of the Designated Class. The
provisions of the Distribution Plan relating to operating policies as well as
initial approval, renewal, amendment and termination are substantially identical
as they relate to each class of shares covered by the Distribution Plan.
 
FEATURES UNIQUE TO EACH CLASS OF SHARES:  There are certain features of the
Distribution Plan that are unique to each class of shares, as described below.
 
CLASS A SHARES.  Class A shares are generally offered pursuant to an initial
sales charge, a substantial portion of which is paid to or retained by the
dealer making the sale (the remainder of which is paid to MFD). See "Purchases
- -- Class A Shares" above. In addition to the initial sales
 
                                       32
<PAGE>   152
 
charge, the dealer also generally receives the ongoing 0.25% per annum service
fee, as discussed above.
 
The distribution fee paid to MFD under the Distribution Plan is equal, on an
annual basis, to 0.10% of the Fund's average daily net assets attributable to
Class A shares. As noted above, MFD may use the distribution fee to cover
distribution-related expenses incurred by it under its distribution agreement
with the Fund, including commissions to dealers and payments to wholesalers
employed by MFD (e.g., MFD pays commission to dealers with respect to purchases
of $1 million or more and purchases by certain retirement plans of Class A
shares which are sold at net asset value but which are subject to a 1% CDSC for
one year after purchase). See "Purchases -- Class A Shares" above. In addition,
to the extent that the aggregate service and distribution fees paid under the
Distribution Plan do not exceed 0.35% per annum of the average daily net assets
of the Fund attributable to Class A shares, the Fund is permitted to pay such
distribution-related expenses or other distribution-related expenses.
 
CLASS B SHARES.  Class B shares are offered at net asset value without an
initial sales charge but subject to a CDSC. See "Purchases -- Class B Shares"
above. MFD will advance to dealers the first year service fee described above at
a rate equal to 0.25% of the purchase price of such shares and, as compensation
therefor, MFD may retain the service fee paid by the Fund with respect to such
shares for the first year after purchase. Dealers will become eligible to
receive the ongoing 0.25% per annum service fee with respect to such shares
commencing in the thirteenth month following purchase.
 
Under the Distribution Plan, the Fund pays MFD a distribution fee equal, on an
annual basis, to 0.75% of the Fund's average daily net assets attributable to
Class B shares. As noted above, this distribution fee may be used by MFD to
cover its distribution-related expenses under its distribution agreement with
the Fund (including the 3.75% commission it pays to dealers upon purchase of
Class B shares, as described under "Purchases -- Class B Shares" above).
 
CLASS C SHARES.  Class C shares are offered at net asset value without an
initial sales charge but subject to a CDSC. See "Purchases -- Class C Shares"
above. MFD will pay a commission to dealers of 1.00% of the purchase price of
Class C shares purchased through dealers at the time of purchase. In
compensation for this 1.00% commission paid by MFD to dealers, MFD will retain
the 1.00% per annum Class C distribution and service fees paid by the Fund with
respect to such shares for the first year after purchase, and dealers will
become eligible to receive from MFD the ongoing 1.00% per annum distribution and
service fees paid by the Fund to MFD with respect to such shares commencing in
the thirteenth month following purchase.
 
This ongoing 1% fee is comprised of the 0.25% per annum service fee paid to MFD
under the Distribution Plan (which MFD in turn pays to dealers), as discussed
above, and a distribution fee paid to MFD (which MFD also in turn pays to
dealers) under the Distribution Plan equal, on an annual basis, to 0.75% of the
Fund's average daily net assets attributable to Class C shares.
 
CURRENT LEVEL OF DISTRIBUTION AND SERVICE FEES.  The Fund's Class A, Class B and
Class C distribution and service fees for its current fiscal year are 0.25%,
1.00% and 1.00% per annum of the Fund's net assets, respectively. Payment of the
0.10% per annum Class A distribution fee will commence on such date as the
Trustees of the Trust may determine.
 
                                       33
<PAGE>   153
 
DISTRIBUTIONS
 
The Fund intends to pay substantially all of its net investment income for any
calendar year to its shareholders as dividends on an annual basis. In
determining the net investment income available for distributions, the Fund may
rely on projections of its anticipated net investment income over a longer term,
rather than its actual net investment income for the period. The Fund may make
one or more distributions during the calendar year to its shareholders from any
long-term capital gains, and may also make one or more distributions during the
calendar year to its shareholders from short-term capital gains. Shareholders
may elect to receive dividends and capital gain distributions in either cash or
additional shares of the same class with respect to which a distribution is
made. Distribution paid by the Fund with respect to Class A shares will
generally be greater than those paid with respect to Class B and Class C shares
because expenses attributable to Class B and Class C shares will generally be
higher.
 
TAX STATUS
 
   
The Fund is treated as an entity separate from the other series of the Trust for
federal income tax purposes. In order to minimize the taxes the Fund would
otherwise be required to pay, the Fund intends to qualify each year as a
"regulated investment company" under Subchapter M of the Code. Because the Fund
intends to distribute all of its net investment income and net realized capital
gains to its shareholders in accordance with the timing requirements imposed by
the Code, it is not expected that the Fund will be required to pay entity level
federal income or excise taxes, although the Fund's foreign-source income may be
subject to foreign withholding taxes.
    
 
   
Shareholders of the Fund normally will have to pay federal income taxes, and any
state or local taxes on the dividends and capital gain distributions they
receive from the Fund, whether paid in cash or reinvested in additional shares.
A portion of the dividends received from the Fund (but none of the Fund's
capital gain distributions) may qualify for the dividends received deduction for
corporations. Shortly after the end of each calendar year, each shareholder will
be sent a statement setting forth the federal income tax status of all dividends
and distributions for that year, including the portion taxable as ordinary
income, the portion taxable as long-term capital gain (as well as the rate
category or categories under which such gain is taxable), the portion, if any,
representing a return of capital (which is generally free of current taxes but
which results in a basis reduction), and the amount, if any, of federal income
tax withheld.
    
 
Fund distributions will reduce the Fund's net asset value per share.
Shareholders who buy shares shortly before the Fund makes a distribution may
thus pay the full price for the shares and then effectively receive a portion of
the purchase price back as a taxable distribution.
 
The Fund intends to withhold U.S. federal income tax at the rate of 30% (or any
lower rate permitted under an applicable treaty) on taxable dividends and other
payments that are subject to such withholding and that are made to persons who
are neither citizens nor residents of the U.S. The Fund is also required in
certain circumstances to apply backup withholding at the rate of 31% on taxable
dividends and redemption proceeds paid to any shareholder (including a
shareholder who is neither a citizen nor a resident of the U.S.) who does not
furnish to the Fund certain information and certifications or who is otherwise
subject to backup withholding. Backup withholding will not, however, be applied
to payments that have been subject to 30% withholding. Prospective investors
should read the Fund's Account Application for additional
 
                                       34
<PAGE>   154
 
information regarding backup withholding of federal income tax and should
consult their own tax advisers as to the tax consequences to them of an
investment in the Fund.
 
NET ASSET VALUE
 
   
The net asset value per share of each class of shares of the Fund is determined
each day during which the Exchange is open for trading. This determination is
made once each day as of the close of regular trading on the Exchange by
deducting the amount of liabilities attributable to the class from the value of
the Fund's assets attributable to the class and dividing the difference by the
number of shares of the class outstanding. Assets in the Fund's portfolio are
valued on the basis of their market values as described in the SAI. The net
asset value of each class of shares is effective for orders received by the
dealer prior to its calculation and received by MFD prior to the close of that
business day. The Fund has authorized one or more dealers to receive purchase
and redemption orders on behalf of the Fund. Such dealers are authorized to
designate other intermediaries to receive purchase and redemption orders on
behalf of the Fund. The Fund will be deemed to have received a purchase or
redemption order when an authorized dealer or, if applicable, a dealer's
authorized designee, receives the order. Customer orders will be priced at the
net asset value of the Fund next computed after such orders are received by an
authorized dealer or the dealer's authorized designee.
    
 
DESCRIPTION OF SHARES, VOTING RIGHTS AND LIABILITIES
 
The Fund, one of four series of the Trust, has three classes of shares which it
offers to the general public, entitled Class A, Class B and Class C Shares of
Beneficial Interest (without par value). The Fund also has a class of shares
which it offers exclusively to certain institutional investors, entitled Class I
shares. The Trust has reserved the right to create and issue additional classes
and series of shares, in which case each class of shares of a series would
participate equally in the earnings, dividends and assets attributable to that
class of that particular series. Shareholders are entitled to one vote for each
share held and shares of each series would be entitled to vote separately to
approve investment advisory agreements or changes in investment restrictions,
but shares of all series would vote together in the election of Trustees and
selection of accountants. Additionally, each class of shares of a series will
vote separately on any material increases in the fees under the Distribution
Plan or on any other matter that affects solely that class of shares, but will
otherwise vote together with all other classes of shares of the series on all
other matters. The Trust does not intend to hold annual shareholder meetings.
The Declaration of Trust provides that a Trustee may be removed from office in
certain instances (see "Description of Shares, Voting Rights and Liabilities" in
the SAI).
 
Each share of a class of the Fund represents an equal proportionate interest in
the Fund with each other class share, subject to the liabilities of that class.
Shares have no pre-emptive or conversion rights (except as set forth above in
"Purchases -- Conversion of Class B Shares"). Shares are fully paid and
non-assessable. Should the Fund be liquidated, shareholders of each class are
entitled to share pro rata in the net assets attributable to that class
available for distribution to shareholders. Shares will remain on deposit with
the Shareholder Servicing Agent and certificates will not be issued except in
connection with pledges and assignments and in certain other limited
circumstances.
 
                                       35
<PAGE>   155
 
The Trust is an entity of the type commonly known as a "Massachusetts business
trust." Under Massachusetts law, shareholders of such a trust may, under certain
circumstances, be held personally liable as partners for its obligations.
However, the risk of a shareholder incurring financial loss on account of
shareholder liability is limited to circumstances in which both inadequate
insurance (e.g., fidelity bonding and errors and omissions insurance) existed
and the Trust itself was unable to meet its obligations.
 
PERFORMANCE INFORMATION
 
   
From time to time, the Fund will provide total rate of return quotations for
each class of shares and may also quote fund rankings in the relevant fund
category from various sources, such as the Lipper Analytical Securities
Corporation and Wiesenberger Investment Companies Service. Total rate of return
quotations will reflect the average annual percentage change over stated periods
in the value of an investment in each class of shares of the Fund made at the
maximum public offering price of the shares of that class with all distributions
reinvested and which will give effect to the imposition of any applicable CDSC
assessed upon redemptions of the Fund's Class B and Class C shares. Such total
rate of return quotations may be accompanied by quotations which do not reflect
the reduction in value of the initial investment due to the sales charge or the
deduction of a CDSC, and which will therefore be higher. The Fund offers
multiple classes of shares which were initially offered for sale to, and
purchased by, the public on different dates (the class "inception date"). The
calculation of total rate of return for a class of shares which has a later
class inception date than another class of shares of the Fund is based both on
(i) the performance of the Fund's newer class from its inception date and (ii)
the performance of the Fund's oldest class from its inception date up to the
class inception date of the newer class. See the SAI for further information on
the calculation of total rate of return for share classes with different class
inception dates.
    
 
   
The Fund's total rate of return quotations are based on historical performance
and are not intended to indicate future performance. Total rate of return
reflects all components of investment return over a stated period of time. The
Fund's quotations may from time to time be used in advertisements, shareholder
reports or other communications to shareholders. For a discussion of the manner
in which the Fund will calculate its total rate of return, see the SAI. For
further information about the Fund's performance for the fiscal year ended,
August 31, 1998, please see the Fund's Annual Report. A copy of the Annual
Report may be obtained without charge by contacting the Shareholder Servicing
Agent (see back cover for address and phone number). In addition to information
provided in shareholder reports, the Fund may, in its discretion, from time to
time, make a list of all or a portion of its holdings available to investors
upon request.
    
 
EXPENSES
 
The Trust pays the compensation of the Trustees who are not officers of MFS and
all expenses of the Fund (other than those assumed by MFS) including but not
limited to: governmental fees; interest charges; taxes; membership dues in the
Investment Company Institute allocable to the Fund, fees and expenses of
independent auditors, of legal counsel, and of any transfer agent, registrar or
dividend disbursing agent of the Fund; expenses of repurchasing and redeeming
shares and servicing shareholder accounts; expenses of preparing, printing and
mailing prospectus, periodic reports, notices and proxy statements to
shareholders and to governmental officers
                                       36
<PAGE>   156
 
and commissions; brokerage and other expenses connected with the execution,
recording and settlement of portfolio security transactions, insurance premiums;
fees and expenses of State Street Bank and Trust Company, the Trust's Custodian,
for all services to the Fund, including safekeeping of funds and securities and
maintaining required books and accounts; expenses of calculating the net asset
value of shares of the Fund; and expenses of shareholder meetings. Expenses
relating to the issuance, registration and qualification of shares of the Fund
and the preparation, printing and mailing of prospectuses are borne by the Fund
except that the Distribution Agreement with MFD requires MFD to pay for
prospectuses that are to be used to sales purposes. Expenses of the Trust which
are not attributable to a specific series of the Trust are allocated among the
series in a manner believed by management of the Trust to be fair and equitable.
 
   
PROVISION OF ANNUAL AND SEMIANNUAL REPORTS
    
 
   
To avoid sending duplicate copies of materials to households, only one copy of
each Fund annual and semiannual report may be mailed to shareholders having the
same residential address on the Fund's records. However, any shareholder may
call the Shareholder Servicing Agent at 1-800-225-2606 to request that copies of
such reports be sent personally to that shareholder.
    
 
   
10.  SHAREHOLDER SERVICES
    
 
Shareholders with questions concerning the shareholder services described below
or concerning other aspects of the Fund, should contact their investment dealer
or the Shareholder Servicing Agent (see back cover for address and phone
number).
 
ACCOUNT AND CONFIRMATION STATEMENTS -- Each shareholder will receive
confirmation statements showing the transaction activity in his account. At the
end of each calendar year, each shareholder will receive information regarding
the tax status of reportable dividends and distributions for that year (see "Tax
Status" above).
 
DISTRIBUTION OPTIONS -- The following options are available to all accounts
(except Systematic Withdrawal Plan accounts) and may be changed as often as
desired by notifying the Shareholder Servicing Agent:
 
    -- Dividends and capital gain distributions reinvested in additional shares.
       This option will be assigned if no other option is specified.
 
    -- Dividends in cash; capital gain distributions reinvested in additional
       shares.
 
    -- Dividends and capital gain distributions in cash.
 
Reinvestments (net of any tax withholding) will be made in additional full and
fractional shares of the same class of shares at the net asset value in effect
on the record date. Dividends and capital gain distributions in amounts less
than $10 will automatically be reinvested in additional shares of the Fund. If a
shareholder has elected to receive dividends and/or capital gain distributions
in cash, and the postal or other delivery service is unable to deliver checks to
the shareholder's address of record, or the shareholder does not respond to
mailings from the Shareholder Servicing Agent with regard to uncashed
distribution checks, such shareholder's distribution option will automatically
be converted to having all dividends and other distributions reinvested in
additional shares. Any request to change a distribution option must be received
by the Shareholder Servicing Agent by the record date for a dividend or
distribution in order to be
 
                                       37
<PAGE>   157
 
effective for that dividend or distribution. No interest will accrue on amounts
represented by uncashed distribution or redemption checks.
 
INVESTMENT AND WITHDRAWAL PROGRAMS -- For the convenience of shareholders, the
Fund makes available the following programs designed to enable shareholders to
add to their investment in an account with the Fund or withdraw from it with a
minimum of paper work. The programs involve no extra charge to shareholders
(other than a sales charge in the case of certain Class A share purchases) and
may be changed or discontinued at any time by a shareholder or the Fund.
 
LETTER OF INTENT -- If a shareholder (other than a group purchaser as described
in the SAI) anticipates purchasing $50,000 or more of Class A shares of the Fund
alone or in combination with shares of any class of other MFS Funds or MFS Fixed
Fund (a bank collective trust) within a 13-month period (or 36-month period for
purchases of $1 million or more), the shareholder may obtain such shares at the
same reduced sales charge as though the total quantity were invested in one lump
sum, subject to escrow agreements and the appointment of an attorney for
redemptions from the escrow amount if the intended purchases are not completed,
by completing the Letter of Intent section of the Account Application.
 
    RIGHT OF ACCUMULATION -- A shareholder qualifies for cumulative quantity
discounts on purchases of Class A shares when his new investment, together with
the current offering price value of all holdings of Class A, Class B and Class C
shares of that shareholder in the MFS Funds and MFS Fixed Fund (a bank
collective trust), reaches a discount level.
 
    DISTRIBUTION INVESTMENT PROGRAM -- Shares of a particular class of the Fund
may be sold at net asset value (and without any applicable CDSC) through the
automatic reinvestment of dividend and capital gain distributions from the same
class of another MFS Fund. Furthermore, distributions made by the Fund may be
automatically invested at net asset value in shares of the same class of another
MFS Fund, if shares of such fund are available for sale (without a sales charge
and not subject to any applicable CDSC).
 
    SYSTEMATIC WITHDRAWAL PLAN -- A shareholder may direct the Shareholder
Servicing Agent to send him (or anyone he designates) regular periodic payments
based upon the value of his account. Each payment under a Systematic Withdrawal
Plan (a "SWP") must be at least $100, except in certain limited circumstances.
The aggregate withdrawals of Class B and Class C shares in any year pursuant to
a SWP will not be subject to a CDSC and are generally limited to 10% of the
value of the account at the time of the establishment of the SWP. The CDSC will
not be waived in the case of SWP redemptions of Class A shares which are subject
to a CDSC.
 
DOLLAR COST AVERAGING PROGRAMS
 
    AUTOMATIC INVESTMENT PLAN:  Cash investments of $50 or more may be made
through a shareholder's checking account on any day of the month. If the
shareholder does not specify a date, the investment will automatically occur on
the first business day of the month. Required forms are available from the
Shareholder Servicing Agent or investment dealers.
 
    AUTOMATIC EXCHANGE PLAN:  Shareholders having account balances of at least
$5,000 in any MFS Fund may exchange their shares for the same class of shares of
the other MFS Funds (and, in the case of Class C shares, for shares of the MFS
Money Market Fund) under the Automatic Exchange Plan, a dollar cost averaging
program. The Automatic Exchange Plan provides for automatic monthly or quarterly
exchanges of funds from the shareholder's account
 
                                       38
<PAGE>   158
 
in an MFS Fund for investment in the same class of shares of other MFS Funds
selected by the shareholder. Under the Automatic Exchange Plan, exchanges of at
least $50 each may be made to up to six different funds. A shareholder should
consider the objectives and policies of a fund and review its prospectus before
electing to exchange money into such fund through the Automatic Exchange Plan.
No transaction fee is imposed in connection with exchange transactions under the
Automatic Exchange Plan. However, exchanges of shares of MFS Money Market Fund,
MFS Government Money Market Fund or Class A shares of MFS Cash Reserve Fund will
be subject to any applicable sales charge. For federal and (generally) state
income tax purposes, an exchange is treated as a sale of the shares exchanged
and, therefore, could result in a capital gain or loss to the shareholder making
the exchange. See the SAI for further information concerning the Automatic
Exchange Plan. Investors should consult their tax advisers for information
regarding the potential capital gain and loss consequences of transactions under
the Automatic Exchange Plan.
 
Because a dollar cost averaging program involves periodic purchases of shares
regardless of fluctuating share offering prices, a shareholder should consider
his financial ability to continue his purchases through periods of low price
levels. Maintaining a dollar cost averaging program concurrently with a
withdrawal program could be disadvantageous because of the sales charge included
in share purchases in the case of Class A shares and because of the assessment
of the CDSC for certain share redemptions in the case of Class A shares.
 
TAX-DEFERRED RETIREMENT PLANS -- Except as noted under "Purchases -- Class C
shares," shares of the Fund may be purchased by all types of tax-deferred
retirement plans, including IRAs, SEP-IRA plans, 401(k) plans, 403(b) plans and
other corporate pension and profit-sharing plans. Investors should consult with
their tax advisers before establishing any of the tax-deferred retirement plans
described above.
                            ------------------------
 
   
The Fund's SAI, dated January 1, 1999, contains more detailed information about
the Fund, including, but not limited to, information related to (i) the Fund's
investment objective, policies and restrictions, (ii) Trustees, officers and
investment adviser, (iii) portfolio transactions and brokerage commissions, (iv)
the Distribution Plan, (v) the method used to calculate total rate of return
quotations of the Fund, and (vi) various services and privileges provided by the
Fund for the benefit of its shareholders, including additional information with
respect to the exchange privilege.
    
 
                                       39
<PAGE>   159
 
                                   APPENDIX A
 
WAIVERS OF SALES CHARGES
 
   
This Appendix sets forth the various circumstances in which all applicable sales
charges are waived (Section I), the initial sales charge and the CDSC for Class
A shares are waived (Section II), and the CDSC for Class B and Class C shares is
waived (Section III). Some of the following information will not apply to
certain funds in the MFS Family of Funds, depending on which classes of shares
are offered by such fund. As used in this Appendix thereto the term "dealer"
includes any broker, dealer, bank (including bank trust departments), registered
investment adviser, financial planner and any other financial institution having
a selling agreement or other similar agreement with MFS Fund Distributors, Inc.
("MFD").
    
 
I. WAIVERS OF ALL APPLICABLE SALES CHARGES
 
In the following circumstances, the initial charge imposed on purchases of Class
A shares and the CDSC imposed on certain redemptions of Class A shares and on
redemptions of Class B shares, as applicable, are waived:
 
1. DIVIDEND REINVESTMENT
 
  - Shares acquired through dividend or capital gain reinvestment; and
 
  - Shares acquired by automatic reinvestment of distributions of dividends and
    capital gains of any fund in the MFS Funds pursuant to the Distribution
    Investment Program.
 
2. CERTAIN ACQUISITIONS/LIQUIDATIONS
 
  - Shares acquired on account of the acquisition or liquidation of assets of
    other investment companies or personal holding companies.
 
3. AFFILIATES OF AN MFS FUND/CERTAIN DEALERS. SHARES ACQUIRED BY:
 
  - Officers, eligible directors, employees (including retired employees) and
    agents of MFS, Sun Life or any of their subsidiary companies;
 
  - Trustees and retired trustees of any investment company for which MFD serves
    as distributor;
 
  - Employees, directors, partners, officers and trustees of any sub-adviser to
    any MFS Fund;
 
  - Employees or registered representatives of dealers;
 
  - Certain family members of any such individual and their spouses identified
    above and certain trusts, pension, profit-sharing or other retirement plans
    for the sole benefit of such persons, provided the shares are not resold
    except to the MFS Fund which issued the shares; and
 
  - Institutional Clients of MFS or MFS Institutional Advisors, Inc.
 
4. INVOLUNTARY REDEMPTIONS (CDSC WAIVER ONLY)
 
  - Shares redeemed at an MFS Fund's direction due to the small size of a
    shareholder's account. See "Redemptions and Repurchases -- General --
    Involuntary Redemptions/Small Accounts" in the Prospectus.
 
                                       A-1
<PAGE>   160
 
5. RETIREMENT PLANS (CDSC WAIVER ONLY).  Shares redeemed on account of
distributions made under the following circumstances:
 
  INDIVIDUAL RETIREMENT ACCOUNTS ("IRAS")
 
  - Death or disability of the IRA owner.
 
  SECTION 401(a) PLANS ("401(a) PLANS") AND SECTION 403(b) EMPLOYER SPONSORED
PLANS ("ESP PLANS")
 
  - Death, disability or retirement of 401(a) or ESP Plan participant;
 
  - Loan from 401(a) or ESP Plan;
 
  - Financial hardship (as defined in Treasury Regulation Section
    1.401(k)-1(d)(2), as amended from time to time);
 
  - Termination of employment of 401(a) or ESP Plan participant (excluding,
    however, a partial or other termination of the Plan);
 
  - Tax-free return of excess 401(a) or ESP Plan contributions;
 
  - To the extent that redemption proceeds are used to pay expenses (or certain
    participant expenses) of the 401(a) or ESP Plan (e.g., participant account
    fees), provided that the Plan sponsor subscribes to the MFS FUNDamental
    401(k) Plan or another similar recordkeeping system made available by MFS
    Service Center, Inc. (the "Shareholder Servicing Agent"); and
 
  - Distributions from a 401(a) or ESP Plan that has invested its assets in one
    or more of the MFS Funds for more than 10 years from the later to occur of:
    (i) January 1, 1993 or (ii) the date such 401(a) or ESP Plan first invests
    its assets in one or more of the MFS Funds.
 
  - The sales charges will be waived in the case of a redemption of all of the
    401(a) or ESP Plan's shares in all MFS Funds (i.e., all the assets of the
    401(a) or ESP Plan invested in the MFS Funds are withdrawn), unless
    immediately prior to the redemption, the aggregate amount invested by the
    401(a) or ESP Plan in shares of the MFS Funds (excluding the reinvestment of
    distributions) during the prior four years equals 50% or more of the total
    value of the 401(a) or ESP Plan's assets in the MFS Funds, in which case the
    sales charges will not be waived.
 
   
  - Shares purchased by certain retirement plans or trust accounts if: (i) the
    plan is currently a party to a retirement plan recordkeeping or
    administrative services agreement with MFD or one of its affiliates and (ii)
    the shares purchased or redeemed represent transfers from or transfers to
    plan investments other than the MFS Funds of which retirement plan
    recordkeeping services are provided under the terms of such agreement.
    
 
  SECTION 403(b) SALARY REDUCTION ONLY PLANS ("SRO PLANS")
 
  - Death or disability of SRO Plan participant.
 
                                       A-2
<PAGE>   161
 
6. CERTAIN TRANSFERS OF REGISTRATION (CDSC WAIVER ONLY). Shares transferred:
 
  - To an IRA rollover account where any sales charges with respect to the
    shares being reregistered would have been waived had they been redeemed; and
 
  - From a single account maintained for a 401(a) Plan to multiple accounts
    maintained by the Shareholder Servicing Agent on behalf of individual
    participants of such Plan, provided that the Plan sponsor subscribes to the
    MFS FUNDamental 401(k) Plan or another similar recordkeeping system made
    available by the Shareholder Servicing Agent.
 
7. LOAN REPAYMENTS.
 
  - Shares acquired pursuant to repayments by retirement plan participants of
    loans from 401(a) or ESP Plans with respect to which such Plan or its
    sponsoring organization subscribes to the MFS FUNDamental 401(k) Program or
    the MFS Recordkeeper Plus Program (but not the MFS Recordkeeper Program).
 
II. WAIVERS OF CLASS A SALES CHARGES
 
In addition to the waivers set forth in Section I above, in the following
circumstances the initial sales charge imposed on purchases of Class A shares
and the CDSC imposed on certain redemptions of Class A shares are waived:
 
1. WRAP ACCOUNT AND FUND "SUPERMARKET" INVESTMENTS
 
  - Shares acquired by investments through certain dealers (including registered
    investment advisers and financial planners) which have established certain
    operational arrangements with MFD which include a requirement that such
    shares be sold for the sole benefit of clients participating in a "wrap"
    account, mutual fund "supermarket" account or a similar program under which
    such clients pay a fee to such dealer.
 
2. INVESTMENT BY INSURANCE COMPANY SEPARATE ACCOUNTS
 
  - Shares acquired by insurance company separate accounts.
 
3. RETIREMENT PLANS
 
  ADMINISTRATIVE SERVICES ARRANGEMENTS
 
  - Shares acquired by retirement plans or trust accounts whose third party
    administrators or dealers have entered into an administrative services
    agreement with MFD or one of its affiliates to perform certain
    administrative services, subject to certain operational and minimum size
    requirements specified from time to time by MFD or one or more of its
    affiliates.
 
  REINVESTMENT OF DISTRIBUTIONS FROM QUALIFIED RETIREMENT PLANS
 
  - Shares acquired through the automatic reinvestment in Class A shares of
    Class A or Class B distributions which constitute required withdrawals from
    qualified retirement plans.
 
                                       A-3
<PAGE>   162
 
  SHARES REDEEMED ON ACCOUNT OF DISTRIBUTIONS MADE UNDER THE FOLLOWING
CIRCUMSTANCES:
 
  IRAS
 
  - Distributions made on or after the IRA owner has attained the age of 59 1/2
    years old; and
 
  - Tax-free returns of excess IRA contributions.
 
  401(a) PLANS
 
  - Distributions made on or after the 401(a) Plan participant has attained the
    age of 59 1/2 years old; and
 
  - Certain involuntary redemptions and redemptions in connection with certain
    automatic withdrawals from a 401(a) Plan.
 
  ESP PLANS AND SRO PLANS
 
  - Distributions made on or after the ESP or SRO Plan participant has attained
    the age of 59 1/2 years old.
 
4. PURCHASE OF AT LEAST $5 MILLION (CDSC WAIVER ONLY)
 
  - Shares acquired of Eligible Funds (as defined below) if the shareholder's
    investment equals or exceeds $5 million in one or more Eligible Funds (the
    "Initial Purchase") (this waiver applies to the shares acquired from the
    Initial Purchase and all shares of Eligible Funds subsequently acquired by
    the shareholder); provided that the dealer through which the Initial
    Purchase is made enters into an agreement with MFD to accept delayed payment
    of commissions with respect to the Initial Purchase and all subsequent
    investments by the shareholder in the Eligible Funds subject to such
    requirements as may be established from time to time by MFD (for a schedule
    of the amount of commissions paid by MFD to the dealer on such investments
    see "Purchases -- Class A Shares -- Purchases subject to a CDSC" in the
    Prospectus). The Eligible Funds are all funds included in the MFS Family of
    Funds, except for Massachusetts Investors Trust, Massachusetts Investors
    Growth Stock Fund, MFS Municipal Bond Fund, MFS Municipal Limited Maturity
    Fund, MFS Money Market Fund, MFS Government Money Market Fund and MFS Cash
    Reserve Fund.
 
   
5. BANK TRUST DEPARTMENTS AND LAW FIRMS
    
 
   
  - Shares acquired by certain bank trust departments or law firms acting as
    trustee or manager for trust accounts which have entered into an
    administrative services agreement with MFS and are acquiring such shares for
    the benefit of their trust account clients.
    
 
   
6. INVESTMENT OF PROCEEDS FROM CERTAIN REDEMPTIONS OF CLASS I SHARES
    
 
   
  - The initial sales charge imposed on purchases of Class A shares, and the
    contingent deferred sales charge imposed on certain redemptions of Class A
    shares, are waived with respect to Class A shares acquired of any of the MFS
    Funds through the immediate reinvestment of the proceeds of a redemption of
    Class I shares of any of the MFS Funds.
    
 
                                       A-4
<PAGE>   163
 
III. WAIVERS OF CLASS B AND CLASS C SALES CHARGES
 
  - In addition to the waivers set forth in Section I above, in the following
    circumstances the CDSC imposed on redemptions of Class B shares is waived:
 
1. SYSTEMATIC WITHDRAWAL PLAN
 
  - Systematic Withdrawal Plan redemptions with respect to up to 10% per year
    (or 15% per year, in the case of accounts registered as IRAs where the
    redemption is made pursuant to Section 72(t) of the Internal Revenue Code of
    1986, as amended) of the account value at the time of establishment.
 
2. DEATH OF OWNER
 
  - Shares redeemed on account of the death of the account owner if the shares
    are held solely in the deceased individual's name or in a living trust for
    the benefit of the deceased individual.
 
3. DISABILITY OF OWNER
 
  - Shares redeemed on account of the disability of the account owner if shares
    are held either solely or jointly in the disabled individual's name or in a
    living trust for the benefit of the disabled individual (in which case a
    disability certification form is required to be submitted to the Shareholder
    Servicing Agent).
 
4. RETIREMENT PLANS.  Shares redeemed on account of distributions made under the
   following circumstances:
 
  IRAS, 401(a) PLANS, ESP PLANS AND SRO PLANS
 
  - Distributions made on or after the IRA owner or the 401(a), ESP or SRO Plan
    participant, as applicable, has attained the age of 70 1/2 years old, but
    only with respect to the minimum distribution under applicable Internal
    Revenue Code ("Code") rules.
 
  SALARY REDUCTION SIMPLIFIED EMPLOYEE PENSION PLANS ("SAR-SEP PLANS")
 
  - Distributions made on or after the SAR-SEP Plan participant has attained the
    age of 70 1/2 years old, but only with respect to the minimum distribution
    under applicable Code rules; and
 
  - Death or disability of a SAR-SEP Plan participant.
 
                                       A-5
<PAGE>   164
 
Investment Adviser
Massachusetts Financial
Services Company
500 Boylston Street
Boston, MA 02116
(617) 954-5000
Distributor
MFS Fund Distributors, Inc.
500 Boylston Street
Boston, MA 02116
(617) 954-5000
Custodian and Dividend
Disbursing Agent
State Street Bank and Trust Company
225 Franklin Street
Boston, MA 02110
 
Shareholder Servicing Agent
MFS Service Center, Inc.
500 Boylston Street
Boston, MA 02116
Toll-free: (800) 225-2606
Mailing Address:
P.O. Box 2281
Boston, MA 02107-9906
 
Independent Auditors
Deloitte & Touche LLP
125 Summer Street
Boston, MA 02110
<PAGE>   165
 
[MFS Investment Management LOGO]
MFS(R) MID CAP GROWTH FUND
 
(A Member of the MFS Family of Funds(R))
                                             STATEMENT OF
                                             ADDITIONAL INFORMATION
 
   
                                             January 1, 1999
    
 
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<TABLE>
<CAPTION>
                                                                   Page
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<C>  <S>                                                           <C>
 1.  Definitions.................................................     2
 2.  Investment Objective, Policies and Restrictions.............     2
          Certain Securities and Investment Techniques...........     2
 3.  Management of the Fund......................................    13
          Trustees...............................................    13
          Officers...............................................    13
          Trustee Compensation Table.............................    14
          Investment Adviser.....................................    14
          Administrator..........................................    15
          Custodian..............................................    15
          Shareholder Servicing Agent............................    15
          Distributor............................................    15
 4.  Portfolio Transactions and Brokerage Commissions............    16
 5.  Shareholder Services........................................    17
          Investment and Withdrawal Programs.....................    17
          Exchange Privilege.....................................    19
          Tax-Deferred Retirement Plans..........................    20
 6.  Tax Status..................................................    20
 7.  Determination of Net Asset Value and Performance............    22
 8.  Distribution Plan...........................................    24
 9.  Description of Shares, Voting Rights and Liabilities........    25
10.  Independent Auditors and Financial Statements...............    26
     Appendix A..................................................   A-1
</TABLE>
    
 
MFS MID CAP GROWTH FUND
A Series of MFS Series Trust IV
500 Boylston Street, Boston, Massachusetts 02116
(617) 954-5000
 
   
This Statement of Additional Information, as amended or supplemented from time
to time (the "SAI"), sets forth information which may be of interest to
investors but which is not necessarily included in the Fund's Prospectus, dated
January 1, 1999. This SAI should be read in conjunction with the Prospectus, a
copy of which may be obtained without charge by contacting the Shareholder
Servicing Agent (see last page for address and phone number).
    
 
THIS SAI IS NOT A PROSPECTUS AND IS AUTHORIZED FOR DISTRIBUTION TO PROSPECTIVE
INVESTORS ONLY IF PRECEDED OR ACCOMPANIED BY A CURRENT PROSPECTUS.
<PAGE>   166
 
1. DEFINITIONS
 
   
<TABLE>
<S>                        <C>   <C>
"Fund"                     --    MFS Mid Cap Growth Fund, a
                                 non-diversified series of
                                 MFS Series Trust IV (the
                                 "Trust"), a Massachusetts
                                 business trust. The Fund
                                 was known as MFS OTC Fund
                                 until its name was changed
                                 on August 29, 1997, and the
                                 Trust was known as
                                 Massachusetts Cash
                                 Management Trust until its
                                 name was changed on August
                                 27, 1993.
"MFS" or the "Adviser"     --    Massachusetts Financial
                                 Services Company, a
                                 Delaware corporation.
"MFD"                      --    MFS Fund Distributors,
                                 Inc., a Delaware
                                 corporation.
"Prospectus"               --    The Prospectus of the Fund,
                                 dated January 1, 1999, as
                                 amended or supplemented
                                 from time to time.
</TABLE>
    
 
2. INVESTMENT OBJECTIVE, POLICIES AND
   RESTRICTIONS
 
INVESTMENT OBJECTIVE. The Fund's investment objective is to seek to obtain
long-term growth of capital.
 
INVESTMENT POLICIES. The following discussion of the Fund's investment policies
and restrictions supplements, and should be read in conjunction with, the
information set forth in the "Investment Objective and Policies" section of the
Prospectus. Any investment involves risk and there can be no assurance that the
Fund will achieve its investment objective.
 
CERTAIN SECURITIES AND INVESTMENT TECHNIQUES
 
NON-DIVERSIFIED STATUS: The Fund has registered as a "non-diversified"
investment company. As a result, under the Investment Company Act of 1940 (the
"1940 Act") the Fund is limited only by its own investment restrictions as to
the percentage of its assets which may be invested in the securities of any one
issuer. However, in spite of the flexibility under the 1940 Act, the Fund would
still have to meet quarterly diversification requirements under the Internal
Revenue Code of 1986, as amended (the "Code") in order for the Fund to qualify
as a regulated investment company. (See "Tax Status" below for more
information.) As a result of the Code's diversification requirements, the Fund
may not have the latitude to take full advantage of the relative absence of 1940
Act diversification requirements.
 
ZERO COUPON BONDS, DEFERRED INTEREST BONDS AND PIK BONDS: Fixed income
securities that the Fund may invest in include zero coupon bonds, deferred
interest bonds and bonds on which the interest is payable in kind ("PIK bonds").
Zero coupon and deferred interest bonds are debt obligations which are issued or
purchased at a significant discount from face value. The discount approximates
the total amount of interest the bonds will accrue and compound over the period
until maturity or the first interest payment date at a rate of interest
reflecting the market rate of the security at the time of issuance. While zero
coupon bonds do not require the periodic payment of interest, deferred interest
bonds provide for a period of delay before the regular payment of interest
begins. PIK bonds are debt obligations which provide that the issuer thereof
may, at its option, pay interest on such bonds in cash or in the form of
additional debt obligations. Such investments benefit the issuer by mitigating
its need for cash to meet debt service, but also require a higher rate of return
to attract investors who are willing to defer receipt of such cash. Such
investments may experience greater volatility in market value due to changes in
interest rates than debt obligations which make regular payments of interest.
The Fund will accrue income on such investments for tax and accounting purposes,
as required, which is distributable to shareholders and which, because no cash
is received at the time of accrual, may require the liquidation of other
portfolio securities to satisfy the Fund's distribution obligations.
 
   
SECURITIES LENDING: The Fund may seek to increase its income by lending
portfolio securities. Such loans will usually be made only to member banks of
the Federal Reserve System and to member firms (or subsidiaries thereof) of the
New York Stock Exchange (the "Exchange") and would be required to be secured
continuously by collateral in cash, U.S. Government securities or an irrevocable
letter of credit maintained on a current basis at an amount at least equal to
the market value of the securities loaned. The Fund would have the right to call
a loan and obtain the securities loaned at any time on customary industry
settlement notice (which will usually not exceed five days). During the
existence of a loan, the Fund would continue to receive the equivalent of the
interest paid by the issuer on the securities loaned. The Fund would also
receive a fee from the borrower. The Fund would receive compensation based on
investment of cash collateral, less a fee paid to the borrower, if the
collateral is in the form of cash. The Fund would not, however, have the right
to vote any securities having voting rights during the existence of the loan,
but would call the loan in anticipation of an important vote to be taken among
holders of the securities or of the giving or withholding of their consent on a
material matter affecting the investment. As with other extensions of credit,
there are risks of delay in recovery or even loss of rights in the collateral
should the borrower of the securities fail financially. However, the loans would
be made only to firms deemed by the Adviser to be of good standing, and when, in
the judgment of the Adviser, the consideration which could be earned currently
from securities loans of this type justifies the attendant risk. If the Adviser
determines to lend securities, it is not intended that the value of the
securities loaned would exceed 30% of the value of the Fund's total assets.
    
 
REPURCHASE AGREEMENTS: The Fund may enter into repurchase agreements with
sellers who are member firms (or subsidiaries thereof) of the Exchange or
members of the Federal Reserve System, recognized primary U.S. Government
securities dealers or institutions which the Adviser has determined to be of
comparable creditworthiness. The securities that the Fund purchases and holds
through its agent are U.S. Government
                                        2
<PAGE>   167
 
securities, the values of which are equal to or greater than the repurchase
price agreed to be paid by the seller. The repurchase price may be higher than
the purchase price, the difference being income to the Fund, or the purchase and
repurchase prices may be the same, with interest at a standard rate due to the
Fund together with the repurchase price on repurchase. In either case, the
income to the Fund is unrelated to the interest rate on the U.S. Government
securities.
 
   
The repurchase agreement provides that in the event the seller fails to pay the
amount agreed upon on the agreed upon delivery date or upon demand, as the case
may be, the Fund will have the right to liquidate the securities. If, at the
time the Fund is contractually entitled to exercise its right to liquidate the
securities, the seller is subject to a proceeding under the bankruptcy laws or
its assets are otherwise subject to a stay order, the Fund's exercise of its
right to liquidate the securities may be delayed and result in certain losses
and costs to the Fund. The Fund has adopted and follows procedures which are
intended to minimize the risks of repurchase agreements. For example, the Fund
only enters into repurchase agreements after the Adviser has determined that the
seller is creditworthy, and the Adviser monitors that seller's creditworthiness
on an ongoing basis. Moreover, under such agreements, the value of the
securities (which are marked to market every business day) is required to be
greater than the repurchase price, and the Fund has the right to make margin
calls at any time if the value of the securities falls below the agreed upon
collateral.
    
 
"WHEN-ISSUED" SECURITIES: When the Fund commits to purchase a security on a
"when-issued" or "forward delivery" basis, it will set up procedures consistent
with the General Statement of Policy of the Securities and Exchange Commission
(the "SEC") concerning such purchases. Since that policy currently recommends
that an amount of the Fund's assets equal to the amount of the purchase be held
aside or segregated to be used to pay for the commitment, the Fund will always
have liquid assets sufficient to cover any commitments or to limit any potential
risk. However, although the Fund does not intend to make such purchases for
speculative purposes and intends to adhere to the provisions of the SEC policy,
purchases of securities on such bases may involve more risk than other types of
purchases. For example, the Fund may have to sell assets which have been set
aside in order to meet redemptions. Also, if the Fund determines it necessary to
sell the "when-issued" or "forward delivery" securities before delivery, it may
incur a loss because of market fluctuations since the time the commitment to
purchase such securities was made.
 
   
INDEXED SECURITIES: The Fund may purchase securities whose prices are indexed to
the prices of other securities, securities indices, currencies, precious metals
or other commodities, or other financial indicators. Indexed securities
typically, but not always, are debt securities or deposits whose value at
maturity (i.e., principal value) or coupon rate is determined by reference to a
specific instrument or statistic. Gold-indexed securities, for example,
typically provide for a maturity value that depends on the price of gold,
resulting in a security whose price tends to rise and fall together with gold
prices. Currency-indexed securities typically are short-term to
intermediate-term debt securities whose maturity values or interest rates are
determined by reference to the values of one or more specified foreign
currencies, and may offer higher yields than U.S. dollar-denominated securities
of equivalent issuers. Currency-indexed securities may be positively or
negatively indexed; that is, their maturity value may increase when the
specified currency value increases, resulting in a security that performs
similarly to a foreign-denominated instrument, or their maturity value may
decline when foreign currencies increase, resulting in a security whose price
characteristics are similar to a put on the underlying currency.
Currency-indexed securities may also have prices that depend on the values of a
number of different foreign currencies relative to each other. Certain indexed
securities may expose the Fund to the risk of loss of all or a portion of the
principal amount of its investment and/or the interest that might otherwise have
been earned on the amount invested.
    
 
The performance of indexed securities depends to a great extent on the
performance of the security, currency, or other instrument to which they are
indexed, and may also be influenced by interest rate changes in the U.S. and
abroad. At the same time, indexed securities are subject to the credit risks
associated with the issuer of the security, and their values may decline
substantially if the issuer's creditworthiness deteriorates. Indexed securities
may be more volatile than the underlying instrument itself and could involve the
loss of all or a portion of the principal amount of the investment. Recent
issuers of indexed securities have included banks, corporations, and certain
U.S. government agencies.
 
MORTGAGE "DOLLAR ROLL" TRANSACTIONS: As described in the Prospectus, the Fund
may enter into mortgage "dollar roll" transactions pursuant to which it sells
mortgage-backed securities for delivery in the future and simultaneously
contracts to repurchase substantially similar securities on a specified future
date. The Fund records these transactions as sale and purchase transactions
rather than as borrowing transactions. During the roll period, the Fund foregoes
principal and interest paid on the mortgage-backed securities. The Fund is
compensated for the lost interest by the difference between the current sales
price and the lower price for the future purchase (often referred to as the
"drop") as well as by the interest earned on the cash proceeds of the initial
sale. The Fund may also be compensated by receipt of a commitment fee.
 
FOREIGN SECURITIES: The Fund may invest up to 35% (and generally expects to
invest between 0% and 20%) of its net assets in foreign securities which are not
traded on a U.S. exchange (not including American Depositary Receipts). As
discussed in the Prospectus, investing in foreign securities generally
represents a greater degree of risk than investing in domestic securities due to
possible exchange rate fluctuations, less publicly available information, more
volatile markets, less securities regulation, less favorable tax provisions, war
or expropriation. As a result of its investments in foreign securities, the Fund
may receive interest or dividend payments, or the proceeds of the sale or
redemption of such securities, in the foreign currencies in which such
securities are denominated. Under certain circumstances, such as where the
Adviser be-
 
                                        3
<PAGE>   168
 
lieves that the applicable exchange rate is unfavorable at the time the
currencies are received or the Adviser anticipates, for any other reason, that
the exchange rate will improve, the Fund may hold such currencies for an
indefinite period of time. While the holding of currencies will permit the Fund
to take advantage of favorable movements in the applicable exchange rate, such
strategy also exposes the Fund to risk of loss if exchange rates move in a
direction adverse to the Fund's position. Such losses could reduce any profits
or increase any losses sustained by the Fund from the sale or redemption of
securities and could reduce the dollar value of interest or dividend payments
received.
 
AMERICAN DEPOSITARY RECEIPTS: The Fund may invest in American Depositary
Receipts ("ADRs") which are certificates issued by a U.S. depository (usually a
bank) and represent a specified quantity of shares of an underlying non-U.S.
stock on deposit with a custodian bank as collateral. ADRs may be sponsored or
unsponsored. A sponsored ADR is issued by a depository which has an exclusive
relationship with the issuer of the underlying security. An unsponsored ADR may
be issued by any number of U.S. depositories. Under the terms of most sponsored
arrangements, depositaries agree to distribute notices of shareholder meetings
and voting instructions, and to provide shareholder communications and other
information to the ADR holders at the request of the issuer of the deposited
securities. The depositary of an unsponsored ADR, on the other hand, is under no
obligation to distribute shareholder communications received from the issuer of
the deposited securities or to pass through voting rights to ADR holders in
respect of the deposited securities. The Fund may invest in either type of ADR.
Although the U.S. investor holds a substitute receipt of ownership rather than
direct stock certificates, the use of the depository receipts in the United
States can reduce costs and delays as well as potential currency exchange and
other difficulties. The Fund may purchase securities in local markets and direct
delivery of these ordinary shares to the local depository of an ADR agent bank
in the foreign country. Simultaneously, the ADR agents create a certificate
which settles at the Fund's custodian in five days. The Fund may also execute
trades on the U.S. markets using existing ADRs. A foreign issuer of the security
underlying an ADR is generally not subject to the same reporting requirements in
the United States as a domestic issuer. Accordingly the information available to
a U.S. investor will be limited to the information the foreign issuer is
required to disclose in its own country and the market value of an ADR may not
reflect undisclosed material information concerning the issuer of the underlying
security. ADRs may also be subject to exchange rate risks if the underlying
foreign securities are denominated in foreign currency.
 
CORPORATE ASSET-BACKED SECURITIES: The Fund may invest in corporate asset-backed
securities. These securities, issued by trusts and special purpose corporations,
are backed by a pool of assets, such as credit card and automobile loan
receivables, representing the obligations of a number of different parties.
 
Corporate asset-backed securities present certain risks. For instance, in the
case of credit card receivables, these securities may not have the benefit of
any security interest in the related collateral. Credit card receivables are
generally unsecured and the debtors are entitled to the protection of a number
of state and federal consumer credit laws, many of which give such debtors the
right to set off certain amounts owed on the credit cards, thereby reducing the
balance due. Most issuers of automobile receivables permit the servicers to
retain possession of the underlying obligations. If the servicer were to sell
these obligations to another party, there is a risk that the purchaser would
acquire an interest superior to that of the holders of the related automobile
receivables. In addition, because of the large number of vehicles involved in a
typical issuance and technical requirements under state laws, the trustee for
the holders of the automobile receivables may not have a proper security
interest in all of the obligations backing such receivables. Therefore, there is
the possibility that recoveries on repossessed collateral may not, in some
cases, be available to support payments on these securities.
 
Corporate asset-backed securities are often backed by a pool of assets
representing the obligations of a number of different parties. To lessen the
effect of failures by obligors to make payments on underlying assets, the
securities may contain elements of credit support which fall into two
categories: (i) liquidity protection and (ii) protection against losses
resulting from ultimate default by an obligor on the underlying assets.
Liquidity protection refers to the provision of advances, generally by the
entity administering the pool of assets, to ensure that the receipt of payments
on the underlying pool occurs in a timely fashion. Protection against losses
resulting from ultimate default ensures payment through insurance policies or
letters of credit obtained by the issuer or sponsor from third parties. The Fund
will not pay any additional or separate fees for credit support. The degree of
credit support provided for each issue is generally based on historical
information respecting the level of credit risk associated with the underlying
assets. Delinquency or loss in excess of that anticipated or failure of the
credit support could adversely affect the return on an investment in such a
security.
 
   
RISKS OF INVESTING IN LOWER RATED BONDS: The Fund may invest in non-convertible
fixed income securities rated Baa by Moody's Investors Service, Inc. ("Moody's")
or BBB by Standard & Poor's Ratings Services ("S&P"), Duff & Phelps Credit
Rating, Co. ("Duff & Phelps") or Fitch IBCA ("Fitch") and comparable unrated
securities. These securities, while normally exhibiting adequate protection
parameters, have speculative characteristics and changes in economic conditions
or other circumstances are more likely to lead to a weakened capacity to make
principal and interest payments than in the case of higher grade fixed income
securities.
    
 
   
The Fund may also invest in fixed income securities rated Ba or lower by Moody's
or BB or lower by S&P, Duff & Phelps or Fitch and comparable unrated securities
(commonly known as "junk bonds") to the extent described in the Prospectus. No
minimum rating standard is required by the Fund. These securities are considered
speculative and, while generally providing greater income than investments in
higher rated securities, will involve greater risk of principal and income
(including the possibility of default or bankruptcy of the issuers of such
securities) and may involve greater volatility of price (especially during
periods of economic uncertainty or change) than securities in the higher
    
 
                                        4
<PAGE>   169
 
rating categories and because yields vary over time, no specific level of income
can ever be assured. These lower rated high yielding fixed income securities
generally tend to reflect economic changes (and the outlook for economic
growth), short-term corporate and industry developments and the market's
perception of their credit quality (especially during times of adverse
publicity) to a greater extent than higher rated securities which react
primarily to fluctuations in the general level of interest rates (although these
lower rated fixed income securities are also affected by changes in interest
rates). In the past, economic downturns or an increase in interest rates have,
under certain circumstances, caused a higher incidence of default by the issuers
of these securities and may do so in the future, especially in the case of
highly leveraged issuers. The prices for these securities may be affected by
legislative and regulatory developments. For example, federal rules require that
savings and loan associations gradually reduce their holdings of high-yield
securities. An effect of such legislation may be to depress the prices of
outstanding lower rated high yielding fixed income securities. The market for
these lower rated fixed income securities may be less liquid than the market for
investment grade fixed income securities. Furthermore, the liquidity of these
lower rated securities may be affected by the market's perception of their
credit quality. Therefore, the Adviser's judgment may at times play a greater
role in valuing these securities than in the case of investment grade fixed
income securities, and it also may be more difficult during times of certain
adverse market conditions to sell these lower rated securities to meet
redemption requests or to respond to changes in the market.
 
While the Adviser may refer to ratings issued by established credit rating
agencies, it is not the Fund's policy to rely exclusively on ratings issued by
these rating agencies, but rather to supplement such ratings with the Adviser's
own independent and ongoing review of credit quality. To the extent the Fund
invests in these lower rated securities, the achievement of its investment
objectives may be more dependent on the Adviser's own credit analysis than in
the case of a fund investing in higher quality fixed income securities. These
lower rated securities may also include zero coupon bonds, deferred interest
bonds and bonds on which interest is payable in kind ("PIK Bonds") which are
described above.
 
OPTIONS ON SECURITIES: The Fund may write (sell) covered call and put options on
securities and purchase call and put options on securities. The Fund may write
options on securities for the purpose of increasing its return on such
securities and for hedging purposes.
 
   
A call option written by the Fund is covered if the Fund owns the security
underlying the call or has an absolute and immediate right to acquire such
security without additional cash consideration (or for additional cash
consideration segregated by the Fund) upon conversion or exchange of other
securities held in its portfolio. A call option is also covered if a Fund holds
a call on the same security and in the same principal amount as the call written
where the exercise price of the call held (a) is equal to or less than the
exercise price of the call written or (b) is greater than the exercise price of
the call written if liquid assets representing the difference are segregated by
the Fund. A put option written by the Fund is covered if the Fund segregates
liquid assets with a value equal to the exercise price, or else holds a put on
the same security and in the same principal amount as the put written where the
exercise price of the put held (i) is equal to or greater than the exercise
price of the put written or (ii) is less than the exercise price of the put
written if liquid assets representing the difference are segregated by the Fund
in assets. Put and call options written by the Fund may also be covered in such
other manner as may be in accordance with the requirements of the exchange on
which, or the counterparty with which, the option is traded, and applicable laws
and regulations.
    
 
Effecting a closing transaction in the case of a written call option will permit
the Fund to write another call option on the underlying security with either a
different exercise price or expiration date or both, or in the case of a written
put option will permit the Fund to write another put option to the extent that
the exercise price thereof is secured by deposited cash or short-term
securities. Such transactions permit the Fund to generate additional premium
income, which will partially offset declines in the value of portfolio
securities or increases in the cost of securities to be acquired. Also,
effecting a closing transaction will permit the proceeds from the concurrent
sale of any securities subject to the option to be used for other investments of
the Fund, provided that another option on such security is not written. If the
Fund desires to sell a particular security from its portfolio on which it has
written a call option, it will effect a closing transaction in connection with
the option prior to or concurrent with the sale of the security.
 
The Fund will realize a profit from a closing transaction if the premium paid in
connection with the closing of an option written by the Fund is less than the
premium received from writing the option, or if the premium received in
connection with the closing of an option purchased by the Fund is more than the
premium paid for the original purchase. Conversely, the Fund will suffer a loss
if the premium paid or received in connection with a closing transaction is more
or less, respectively, than the premium received or paid in establishing the
option position. Because increases in the market price of a call option will
generally reflect increases in the market price of the underlying security, any
loss resulting from the closing out of a call option previously written by the
Fund is likely to be offset in whole or in part by appreciation of the
underlying security owned by the Fund.
 
The Fund may write options in connection with buy-and-write transactions; that
is, the Fund may purchase a security and then write a call option against that
security. The exercise price of the call option the Fund determines to write
will depend upon the expected price movement of the underlying security. The
exercise price of a call option may be below ("in-the-money"), equal to
("at-the-money") or above ("out-of-the-money") the current value of the
underlying security at the time the option is written. If the call options are
exercised in such transactions, the Fund's maximum gain will be the premium
received by it for writing the option, adjusted upwards or downwards by the
difference between the Fund's purchase price of the security and
                                        5
<PAGE>   170
 
the exercise price, less related transaction costs. If the options are not
exercised and the price of the underlying security declines, the amount of such
decline will be offset in part, or entirely, by the premium received.
 
The writing of covered put options is similar in terms of risk/return
characteristics to buy-and-write transactions. Put options could be used by the
Fund in the same market environments that call options would be used in
equivalent buy-and-write transactions.
 
The Fund may write combinations of put and call options on the same security, a
practice known as a "straddle." By writing a straddle, the Fund undertakes a
simultaneous obligation to sell and purchase the same security in the event that
one of the options is exercised. If the price of the security subsequently rises
sufficiently above the exercise price to cover the amount of the premium and
transaction costs, the call will likely be exercised and the Fund will be
required to sell the underlying security at a below market price. This loss may
be offset, however, in whole or in part, by the premiums received on the writing
of the two options. Conversely, if the price of the security declines by a
sufficient amount, the put will likely be exercised. The writing of straddles
will likely be effective, therefore, only where the price of a security remains
stable and neither the call nor the put is exercised. In an instance where one
of the options is exercised, the loss on the purchase or sale of the underlying
security may exceed the amount of the premiums received.
 
By writing a call option, the Fund limits its opportunity to profit from any
increase in the market value of the underlying security above the exercise price
of the option. By writing a put option, the Fund assumes the risk that it may be
required to purchase the underlying security for an exercise price above its
then current market value, resulting in a capital loss unless the security
subsequently appreciates in value. The writing of options on securities will be
undertaken by the Fund for purposes in addition to hedging, and could involve
certain risks which are not present in the case of hedging transactions.
Moreover, even where options are written for hedging purposes, such transactions
will constitute only a partial hedge against declines in the value of portfolio
securities or against increases in the value of securities to be acquired, up to
the amount of the premium.
 
The Fund also may purchase put and call options on securities. Put options would
be purchased to hedge against a decline in the value of securities held in the
Fund's portfolio. If such a decline occurs, the put options will permit the Fund
to sell the underlying securities at the exercise price, or to close out the
options at a profit. By using put options in this way, the Fund will reduce any
profit it might otherwise have realized in the underlying security by the amount
of the premium paid for the put option and related transaction costs. The Fund
may purchase call options to hedge against an increase in the price of
securities that the Fund anticipates purchasing in the future. If such an
increase occurs, the call option will permit the Fund to purchase the securities
at the exercise price or to close out the option at a profit. The premium paid
for a call or put option plus any transaction costs will reduce the benefit, if
any, realized by the Fund upon exercise of the option, and, unless the price of
the underlying security rose or declined sufficiently, the option may expire
worthless to the Fund.
 
The staff of the SEC has taken the position that purchased over-the-counter
options and assets used to cover written over-the-counter options are illiquid
and, therefore, together with other illiquid securities, cannot exceed a certain
percentage of the Fund's assets (the "SEC illiquidity ceiling"). Although the
Adviser disagrees with this position, the Adviser intends to limit the Fund's
writing of over-the-counter options in accordance with the following procedure.
Except as provided below, the Fund intends to write over-the-counter options
only with primary U.S. Government securities dealers recognized by the Federal
Reserve Bank of New York. Also, the contracts which the Fund has in place with
such primary dealers will provide that the Fund has the absolute right to
repurchase an option it writes at any time at a price which represents the fair
market value, as determined in good faith through negotiation between the
parties, but which in no event will exceed a price determined pursuant to a
formula in the contract. Although the specific formula may vary between
contracts with different primary dealers, the formula will generally be based on
a multiple of the premium received by the Fund for writing the option, plus the
amount, if any, of the option's intrinsic value (i.e., the amount that the
option is in-the-money). The formula may also include a factor to account for
the difference between the price of the security and the strike price of the
option if the option is written out-of-money. The Fund will treat all or a part
of the formula price as illiquid for purposes of the SEC illiquidity ceiling.
The Fund may also write over-the-counter options with non-primary dealers,
including foreign dealers, and will treat the assets used to cover these options
as illiquid for purposes of such SEC illiquidity ceiling.
 
OPTIONS ON STOCK INDICES: The Fund may write (sell) covered call and put options
on stock indices and purchase call and put options on stock indices for the
purpose of increasing its gross income and to protect its portfolio against
declines in the value of securities it owns or increases in the value of
securities to be acquired.
 
   
The Fund may cover call options on stock indices by owning securities whose
price changes, in the opinion of the Adviser, are expected to be similar to
those of the index, or by having an absolute and immediate right to acquire such
securities without additional cash consideration (or for additional cash
consideration held in a segregated account by its custodian) upon conversion or
exchange of other securities in its portfolio. Nevertheless, where the Fund
covers a call option on a stock index through ownership of securities, such
securities may not match the composition of the index and, in that event, the
Fund will not be fully covered and could be subject to risk of loss in the event
of adverse changes in the value of the index. The Fund may also cover call
options on stock indices by holding a call on the same index and in the same
principal amount as the call written where the exercise price of the call held
(a) is equal to or less than the exercise price of the call written or (b) is
greater than the exercise price of the call written if liquid assets
    
 
                                        6
<PAGE>   171
 
   
representing the difference are segregated by the Fund. The Fund may cover put
options on stock indices by segregating liquid assets with a value equal to the
exercise price, or else by holding a put on the same security and in the same
principal amount as the put written where the exercise price of the put held (a)
is equal to or greater than the exercise price of the put written or (b) is less
than the exercise price of the put written if liquid assets representing the
difference are segregated by the Fund. Put and call options on stock indices
written by the Fund may also be covered in such other manner as may be in
accordance with the rules of the exchange on which, or the counterparty with
which, the option is traded, and applicable laws and regulations.
    
 
The Fund will receive a premium from writing a put or call option, which
increases the Fund's gross income in the event the option expires unexercised or
is closed out at a profit. If the value of an index on which the Fund has
written a call option falls or remains the same, the Fund will realize a profit
in the form of the premium received (less transaction costs) that could offset
all or a portion of any decline in the value of the securities it owns. If the
value of the index rises, however, the Fund will realize a loss in its call
option position, which will reduce the benefit of any unrealized appreciation in
the Fund's stock investments. By writing a put option, the Fund assumes the risk
of a decline in the index. To the extent that the price changes of securities
owned by a Fund correlate with changes in the value of the index, writing
covered put options on indices will increase the Fund's losses in the event of a
market decline, although such losses will be offset in part by the premium
received for writing the option.
 
The purchase of call options on stock indices may be used by the Fund to attempt
to reduce the risk of missing a broad market advance, or an advance in an
industry or market segment, at a time when the Fund holds uninvested cash or
short-term debt securities awaiting investment. When purchasing call options for
this purpose, the Fund will also bear the risk of losing all or a portion of the
premium paid, and related transaction costs, if the value of the index does not
rise. The purchase of call options on stock indices when the Fund is
substantially fully invested is a form of leverage, up to the amount of the
premium and related transaction costs, and involves risks of loss and of
increased volatility similar to those involved in purchasing calls on securities
the Fund owns.
 
The Fund also may purchase put options on stock indices to hedge its investments
against a decline in value. By purchasing a put option on a stock index, the
Fund will seek to offset a decline in the value of securities it owns through
appreciation of the put option. If the value of the Fund's investments does not
decline as anticipated, or if the value of the option does not increase, the
Fund's loss will be limited to the premium paid for the option, plus related
transaction costs. The success of this strategy will largely depend on the
accuracy of the correlation between the changes in value of the index and the
changes in value of the Fund's security holdings.
 
YIELD CURVE OPTIONS: The Fund may also enter into options on the "spread," or
yield differential, between two fixed income securities, in transactions
referred to as "yield curve" options. In contrast to other types of options, a
yield curve option is based on the difference between the yields of designated
securities, rather than the prices of the individual securities, and is settled
through cash payments. Accordingly, a yield curve option is profitable to the
holder if this differential widens (in the case of a call) or narrows (in the
case of a put), regardless of whether the yields of the underlying securities
increase or decrease.
 
   
Yield curve options may be used for the same purposes as other options on
securities. Specifically, the Fund may purchase or write such options for
hedging purposes. For example, the Fund may purchase a call option on the yield
spread between two securities, if it owns one of the securities and anticipates
purchasing the other security and wants to hedge against an adverse change in
the yield spread between the two securities. The Fund may also purchase or write
yield curve options for other than hedging purposes (i.e., in an effort to
increase its current income) if, in the judgment of the Adviser, the Fund will
be able to profit from movements in the spread between the yields of the
underlying securities. The trading of yield curve options is subject to all of
the risks associated with the trading of other types of options. In addition,
however, such options present risk of loss even if the yield of one of the
underlying securities remains constant, if the spread moves in a direction or to
an extent which was not anticipated. Yield curve options written by the Fund
will be "covered." A call (or put) option is covered if the Fund holds another
call (or put) option on the spread between the same two securities and
segregates liquid assets sufficient to cover the Fund's net liability under the
two options. Therefore, the Fund's liability for such a covered option is
generally limited to the difference between the amount of the Fund's liability
under the option written by the Fund less the value of the option held by the
Fund. Yield curve options may also be covered in such other manner as may be in
accordance with the requirements of the counterparty with which the option is
traded and applicable laws and regulations. Yield curve options are traded
over-the-counter and because they have been only recently introduced,
established trading markets for these securities have not yet developed. Because
these securities are traded over-the-counter, the SEC has taken the position
that yield curve options are illiquid and, therefore, cannot exceed the SEC
illiquidity ceiling. See "Options on Securities" above for a discussion of the
policies the Adviser intends to follow to limit the Fund's investment in these
securities.
    
 
OPTIONS ON FOREIGN CURRENCIES: The Fund may purchase and write put and call
options on foreign currencies ("Options on Foreign Currencies") for the purpose
of protecting against declines in the dollar value of foreign portfolio
securities and against increases in the dollar cost of foreign securities to be
acquired. For example, a decline in the dollar value of a foreign currency in
which portfolio securities are denominated will reduce the dollar value of such
securities, even if their value in the foreign currency remains constant. In
order to protect against such diminutions in the value of portfolio securities,
the Fund may purchase put Options on the Foreign Currency. If the
                                        7
<PAGE>   172
 
value of the currency did decline, the Fund would have the right to sell such
currency for a fixed amount in dollars and would thereby offset, in whole or in
part, the adverse effect on its portfolio which otherwise would have resulted.
 
Conversely, where a rise in the dollar value of a currency in which securities
to be acquired are denominated is projected, thereby increasing the cost of such
securities, the Fund may purchase call options thereon. The purchase of such
options could offset, at least partially, the effects of the adverse movements
in exchange rates. As in the case of other types of options, however, the
benefit to the Fund deriving from purchases of Options on Foreign Currencies
would be reduced by the amount of the premium and related transaction costs. In
addition, where currency exchange rates do not move in the direction or to the
extent anticipated, the Fund could sustain losses on transactions in Options on
Foreign Currencies which would require it to forego a portion or all of the
benefits of advantageous changes in such rates.
 
The Fund may write Options on Foreign Currencies for the same types of hedging
purposes. For example, where the Fund anticipates a decline in the dollar value
of foreign-denominated securities due to adverse fluctuations in exchange rates
it may, instead of purchasing a put option, write a call option on the relevant
currency. If the expected decline occurred, the option would most likely not be
exercised, and the diminution in value of portfolio securities would be offset
by the amount of the premium received less related transaction costs. As in the
case of other types of options, therefore, the writing of Options on Foreign
Currencies will constitute only a partial hedge.
 
FUTURES CONTRACTS: The Fund may enter into stock index and foreign currency
futures contracts ("Futures Contracts") for hedging purposes or for non-hedging
purposes (which may be speculative) to the extent permitted by applicable law. A
Futures Contract is a bilateral agreement providing for the purchase and sale of
a specified type and amount of a financial instrument, or foreign currency, or
for the making and acceptance of a cash settlement, at a stated time in the
future for a fixed price. By its terms, a Futures Contract provides for a
specified settlement date on which, in the case of the majority of foreign
currency futures contracts, the currency or the contract are delivered by the
seller and paid for by the purchaser, or on which, in the case of stock index
futures contracts and certain foreign currency futures contracts, the difference
between the price at which the contract was entered into and the contract's
closing value is settled between the purchaser and seller in cash. Futures
contracts differ from options in that they are bilateral agreements, with both
the purchaser and the seller equally obligated to complete the transaction.
Futures Contracts call for settlement only on the expiration date and cannot be
"exercised" at any other time during their term.
 
The purchase or sale of a Futures Contract differs from the purchase or sale of
a security or the purchase of an option in that no purchase price is paid or
received. Instead, an amount of cash or cash equivalents, which varies but may
be as low as 5% or less of the value of the contract, must be deposited with the
broker as "initial margin". Subsequent payments to and from the broker, referred
to as "variation margin", are made on a daily basis as the value of the index or
instrument underlying the Futures Contract fluctuates, making positions in the
Futures Contract more or less valuable -- a process known as "marking to the
market."
 
Purchases or sales of stock index futures contracts may be used to attempt to
protect the Fund's current or intended stock investments from broad fluctuations
in stock prices. For example, the Fund may sell stock index futures contracts in
anticipation of or during a market decline to attempt to offset the decrease in
market value of the Fund's securities portfolio that might otherwise result. If
such decline occurs, the loss in value of portfolio securities may be offset, in
whole or part, by gains on the futures position. When the Fund is not fully
invested in the securities market and anticipates a significant market advance,
it may purchase stock index futures contracts in order to gain rapid market
exposure that may, in part or entirely, offset increases in the cost of
securities that the Fund intends to purchase. As such purchases are made, the
corresponding positions in stock index futures contracts will be closed out. In
a substantial majority of these transactions, the Fund will purchase such
securities upon termination of the futures position, but under unusual market
conditions, a long futures position may be terminated without a related purchase
of securities.
 
As noted in the Prospectus, the Fund may purchase and sell foreign currency
futures contracts for hedging purposes, to attempt to protect its current or
intended investments from fluctuations in currency exchange rates. Such
fluctuations could reduce the dollar value of portfolio securities denominated
in foreign currencies, or increase the cost of foreign-denominated securities to
be acquired, even if the value of such securities in the currencies in which
they are denominated remains constant. The Fund may sell futures contracts on a
foreign currency, for example, where it holds securities denominated in such
currency and it anticipates a decline in the value of such currency relative to
the dollar. In the event such decline occurs, the resulting adverse effect on
the value of foreign-denominated securities may be offset, in whole or in part,
by gains on the futures contracts.
 
Conversely, a Fund could protect against a rise in the dollar cost of
foreign-denominated securities to be acquired by purchasing futures contracts on
the relevant currency, which could offset, in whole or in part, the increased
cost of such securities resulting from a rise in the dollar value of the
underlying currencies. Where the Fund purchases futures contracts under such
circumstances, however, and the prices of securities to be acquired instead
decline, the Fund will sustain losses on its futures position which could reduce
or eliminate the benefits of the reduced cost of portfolio securities to be
acquired.
 
OPTIONS ON FUTURES CONTRACTS: The Fund may write or purchase options to buy or
sell Futures Contracts ("Options on Futures Contracts"), for hedging purposes or
for non-hedging purposes (which may be speculative) to the extent permitted by
applicable law. The writing of a call Option on a Futures Contract
 
                                        8
<PAGE>   173
 
constitutes a partial hedge against declining prices of the securities or other
instruments required to be delivered under the terms of the Futures Contract. If
the futures price at expiration of the option is below the exercise price, the
Fund will retain the full amount of the option premium, less related transaction
costs, which provides a partial hedge against any decline that may have occurred
in the Fund's portfolio holdings. The writing of a put Option on a Futures
Contract constitutes a partial hedge against increasing prices of the securities
or other instruments required to be delivered under the terms of the Futures
Contract. If the futures price at expiration of the option is higher than the
exercise price, the Fund will retain the full amount of the option premium, less
related transaction costs, which provides a partial hedge against any increase
in the price of securities which the Fund intends to purchase. If a put or call
option the Fund has written is exercised, the Fund will incur a loss which will
be reduced by the amount of the premium it receives. Depending on the degree of
correlation between changes in the value of its portfolio securities and changes
in the value of its futures positions, the Fund's losses from existing Options
on Futures Contracts may to some extent be reduced or increased by changes in
the value of portfolio securities.
 
   
The Fund may cover the writing of call Options on Futures Contracts (a) through
purchases of the underlying Futures Contract, (b) through ownership of the
instrument, or instruments included in the index, underlying the Futures
Contract, or (c) through the holding of a call on the same Futures Contract and
in the same principal amount as the call written where the exercise price of the
call held (i) is equal to or less than the exercise price of the call written or
(ii) is greater than the exercise price of the call written if liquid assets
representing the difference are segregated by the Fund. The Fund may cover the
writing of put Options on Futures Contracts (a) through sales of the underlying
Futures Contract, (b) through segregation of liquid assets in an amount equal to
the value of the security or index underlying the Futures Contract, or (c)
through the holding of a put on the same Futures Contract and in the same
principal amount as the put written where the exercise price of the put held (i)
is equal to or greater than the exercise price of the put written or (ii) is
less than the exercise price of the put written if liquid assets representing
the difference are segregated by the Fund. Put and Call Options on Futures
Contracts written by the Fund may also be covered in such other manner as may be
in accordance with the rules of the exchange on which, or the counterparty with
which, the option is traded, and applicable laws and regulations. Upon the
exercise of a call Option on a Futures Contract written by the Fund, the Fund
will be required to sell the underlying Futures Contract which, if the Fund has
covered its obligation through the purchase of such Contract, will serve to
liquidate its futures position. Similarly, where a put Option on a Futures
Contract written by the Fund is exercised, the Fund will be required to purchase
the underlying Futures Contract which, if the Fund has covered its obligation
through the sale of such Contract, will close out its futures position.
    
 
The Fund may purchase Options on Futures Contracts for hedging purposes as an
alternative to purchasing or selling the underlying Futures Contracts. For
example, where a decrease in the value of portfolio securities is anticipated as
a result of a projected market-wide decline or changes in interest or exchange
rates, the Fund could, in lieu of selling Futures Contracts, purchase put
options thereon. In the event that such decrease occurs, it may be offset, in
whole or part, by a profit on the option. Conversely, where it is projected that
the value of securities to be acquired by the Fund will increase prior to
acquisition, due to a market advance or changes in interest or exchange rates,
the Fund could purchase call Options on Futures Contracts, rather than
purchasing the underlying Futures Contracts.
 
   
In order to assure that the Fund will not be deemed to be a "commodity pool" for
purposes of the Commodity Exchange Act, regulations of the Commodity Futures
Trading Commission (the "CFTC") require that the Fund enter into transactions in
Futures Contracts, Options on Futures Contracts (including Options on Futures or
Foreign Currencies) traded on a CFTC-regulated exchange only (i) for bona fide
hedging purposes (as defined in CFTC regulations), or (ii) for non-hedging
purposes, provided that the aggregate initial margin and premiums required to
establish such non-bona fide hedging positions does not exceed 5% of the
liquidation value of the Fund's assets after taking into account unrealized
profits and unrealized losses on any such contracts the Fund has entered into,
and excluding, in computing such 5%, the in-the-money amount with respect to an
option that is in-the-money at the time of purchase.
    
 
FORWARD CONTRACTS: The Fund may enter into forward foreign currency exchange
contracts for the purchase or sale of a specific currency at a future date at a
price set at the time of the contract (a "Forward Contract"). The Fund may enter
into Forward Contracts for hedging purposes as well as for non-hedging (which
may be speculative). The Fund may also enter into Forward Contracts for
"cross-hedging" as noted in the Prospectus. Transactions in Forward Contracts
entered into for hedging purposes will include forward purchases or sales of
foreign currencies for the purpose of protecting the dollar value of securities
denominated in a foreign currency or protecting the dollar equivalent of
interest or dividends to be paid on such securities. By entering into such
transactions, however, the Fund may be required to forego the benefits of
advantageous changes in exchange rates. The Fund may also enter into
transactions in Forward Contracts for other than hedging purposes which presents
greater profit potential but also involves increased risk. For example, if the
Adviser believes that the value of a particular foreign currency will increase
or decrease relative to the value of the U.S. dollar, the Fund may purchase or
sell such currency, respectively, through a Forward Contract. If the expected
changes in the value of the currency occur, the Fund will realize profits which
will increase its gross income. Where exchange rates do not move in the
direction or to the extent anticipated, however, the Fund may sustain losses
which will reduce its gross income. Such transactions, therefore, could be
considered speculative.
 
                                        9
<PAGE>   174
 
The Fund has established procedures which require the use of segregated assets
or "cover" in connection with the purchase and sale of such contracts. In those
instances in which the Fund satisfies this requirement through segregation of
assets, it will maintain liquid assets, which will be marked to market on a
daily basis, in an amount equal to the value of its commitments under Forward
Contracts.
 
RISK FACTORS: IMPERFECT CORRELATION OF HEDGING INSTRUMENTS WITH THE FUND'S
PORTFOLIO -- The Fund's ability effectively to hedge all or a portion of its
portfolio through transactions in options, Futures Contracts, and Forward
Contracts will depend on the degree to which price movements in the underlying
index or instrument correlate with price movements in the relevant portion of
the Fund's portfolio. Because the securities in the Fund's portfolio will most
likely not be the same as those securities underlying a stock index, the
correlation between movements in the portfolio and in the securities underlying
the index will not be perfect. The trading of Futures Contracts and options
entails the additional risk of imperfect correlation between movements in the
futures or option price and the price of the underlying index or obligation. The
anticipated spread between the prices may be distorted due to the differences in
the nature of the markets, such as differences in margin requirements, the
liquidity of such markets and the participation of speculators in such markets.
In this regard, trading by speculators in options and Futures Contracts has in
the past occasionally resulted in market distortions, which may be difficult or
impossible to predict, particularly near the expiration of such contracts. It
should be noted that Futures Contracts or options based upon a narrower index of
securities, such as those of a particular industry group, may present greater
risk than options or Futures Contracts based on a broad market index, because a
narrower index is more susceptible to rapid and extreme fluctuations as a result
of changes in the value of a small number of securities. The trading of Options
on Futures Contracts also entails the risk that changes in the value of the
underlying Futures Contracts will not be fully reflected in the value of the
option. Further, with respect to options on securities, options on stock indexes
and Options on Futures Contracts, the Fund is subject to the risk of market
movements between the time that the option is exercised and the time of
performance thereunder. In writing a covered call option on a security, index or
Futures Contract, the Fund also incurs the risk that changes in the value of the
instruments used to cover the position will not correlate closely with changes
in the value of the option or underlying index or instrument.
 
The Fund will invest in a hedging instrument only if, in the judgment of its
Adviser, there would be expected to be a sufficient degree of correlation
between movements in the value of the instrument and movements in the value of
the relevant portion of the Fund's portfolio for such hedge to be effective.
There can be no assurance that the Adviser's judgment will be accurate.
 
It should also be noted that the Fund may enter into transactions in options,
futures contracts, options on futures contracts and forward contracts not only
for hedging purposes, but also for non-hedging purposes, which may include for
speculative purposes, including the purpose of increasing its return on
portfolio securities. As a result, in the event of adverse market movements, the
Fund might be subject to losses, which would not be offset by increases in the
value of portfolio securities or declines in the cost of securities to be
acquired. In addition, the method of covering an option employed by the Fund may
not fully protect it against risk of loss and, in any event, the Fund could
suffer losses on the option position which might not be offset by corresponding
portfolio gains.
 
With respect to the writing of straddles on securities, the Fund incurs the risk
that the price of the underlying security will not remain stable, that one of
the options written will be exercised and that the resulting loss will not be
offset by the amount of the premiums received.
 
POTENTIAL LACK OF A LIQUID SECONDARY MARKET -- Prior to exercise or expiration,
a futures or option position can only be terminated by entering into a closing
purchase or sale transaction. This requires a secondary market for such
instruments on the exchange on which the initial transaction was entered into.
While the Fund will enter into options or futures positions only if there
appears to be a liquid secondary market therefor, there can be no assurance that
such a market will exist for any particular contracts at any specific time. In
that event, it may not be possible to close out a position held by the Fund, and
the Fund could be required to purchase or sell the instrument underlying an
option, make or receive a cash settlement or meet ongoing variation margin
requirements. Under such circumstances, if the Fund had insufficient cash
available to meet margin requirements, it might be necessary to liquidate
portfolio securities at a time when it would be disadvantageous to do so. The
inability to close out options and futures positions, therefore, could have an
adverse impact on the Fund's ability effectively to hedge its portfolios, and
could result in trading losses. The liquidity of a secondary market in a Futures
Contract or options thereon may also be adversely affected by "daily price
fluctuation limits", established by exchanges, which limit the amount of
fluctuation in the price of a contract during a single trading day. The trading
of Futures Contracts and options is also subject to the risk of trading halts,
suspensions, exchange or clearing house equipment failures, government
intervention, insolvency of a brokerage firm or clearing house or other
disruptions of normal trading activity, which could at times make it difficult
or impossible to liquidate existing positions or to recover excess variation
margin payments.
 
MARGIN -- Because of low initial margin deposits made upon the opening of a
futures position and the writing of an option, such transactions involve
substantial leverage. As a result, relatively small movements in the price of
the contract can result in substantial unrealized gains or losses. Because the
Fund would engage in the purchase or sale of Futures Contracts, the writing of
Options on Futures Contracts, and the purchase and writing of options on
securities and stock indexes in part for hedging purposes, any losses incurred
in connection therewith should, if the hedging strategy is successful, be
offset, in whole or in part, by increases in the value of securities held by the
Fund or
                                       10
<PAGE>   175
 
decreases in the prices of securities the Fund intends to acquire. Where the
Fund writes options on securities or options on stock indexes for other than
hedging purposes, the margin requirements associated with such transactions
could expose the Fund to greater risk.
 
TRADING AND POSITION LIMITS -- The exchanges on which Futures Contracts and
options are traded may impose limitations governing the maximum number of
positions on the same side of the market and involving the same underlying
instrument which may be held by a single investor, whether acting alone or in
concert with others (regardless of whether such contracts are held on the same
or different exchanges or held or written in one or more accounts or through one
or more brokers). In addition, the CFTC and the various contract markets have
established limits referred to as "speculative position limits" on the maximum
net long or net short position which any person may hold or control in a
particular futures or option contract. An exchange may order the liquidation of
positions found to be in violation of these limits and it may impose other
sanctions or restrictions. The Adviser does not believe that these trading and
position limits will have any adverse impact on the strategies for hedging the
portfolio of the Fund.
 
RISK OF OPTIONS ON FUTURES CONTRACTS -- The amount of risk the Fund assumes when
it purchases an Option on a Futures Contract is the premium paid for the option,
plus related transaction costs. In order to profit from an option purchased,
however, it may be necessary to exercise the option and to liquidate the
underlying Futures Contract, subject to the risks of the availability of a
liquid offset market described herein. The writer of an Option on a Futures
Contract is subject to the risks of commodity futures trading, including the
requirement of initial and variation margin payments, as well as the additional
risk that movements in the price of the option may not correlate with movements
in the price of the underlying index or Futures Contract.
 
ADDITIONAL RISKS OF TRANSACTIONS NOT CONDUCTED ON EXCHANGES -- Transactions in
Forward Contracts are subject to all of the correlation, liquidity and other
risks outlined above. In addition, however, such transactions are subject to the
risk of governmental actions affecting trading in or the prices of currencies
underlying such contracts, which could restrict or eliminate trading and could
have a substantial adverse effect on the value of positions held by the Fund. In
addition, the value of such positions could be adversely affected by a number of
other complex political and economic factors applicable to the countries issuing
the underlying currencies. Further, unlike trading in most other types of
instruments, there is no systematic reporting of last sale information with
respect to the foreign currencies underlying contracts thereon. As a result, the
available information on which trading systems will be based may not be as
complete as the comparable data on which the Fund makes investment and trading
decisions in connection with other transactions. Moreover, because the foreign
currency market is a global, twenty-four hour market, events could occur on that
market which would not be reflected in the forward markets until the following
day, thereby preventing the Fund from responding to such events in a timely
manner. Settlements of exercises of Forward Contracts generally must occur
within the country issuing the underlying currency, which in turn requires
traders to accept or make delivery of such currencies in conformity with any
United States or foreign restrictions and regulations regarding the maintenance
of foreign banking relationships, fees, taxes or other charges.
 
Forward Contracts, and over-the-counter options on securities, are not traded on
exchanges regulated by the CFTC or the SEC, but through financial institutions
acting as market-makers. In an over-the-counter trading environment, many of the
protections afforded to exchange participants will not be available. In
addition, over-the-counter transactions can only be entered into with a
financial institution willing to take the opposite side, as principal, of the
Fund's position unless the institution acts as broker and is able to find
another counterparty willing to enter into the transaction with the Fund. Where
no such counterparty is available, it will not be possible to enter into a
desired transaction. There also may be no liquid secondary market in the trading
of over-the-counter contracts, and the Fund could be required to retain options
purchased or written, or Forward Contracts entered into, until exercise,
expiration or maturity. This in turn could limit the Fund's ability to profit
from open positions or to reduce losses experienced, and could result in greater
losses. Further, over-the-counter transactions are not subject to the
performance guarantee of an exchange clearing house, and the Fund will therefore
be subject to the risk of default by, or the bankruptcy of, the financial
institution serving as its counterparty.
 
While Forward Contracts are not presently subject to regulation by the CFTC, the
CFTC may in the future assert or be granted authority to regulate such
instruments. In such event, the Fund's ability to utilize Forward Contracts in
the manner set forth above could be restricted.
 
   
The policies stated above are not fundamental and may be changed without
shareholder approval, as may the Fund's investment objective.
    
 
INVESTMENT RESTRICTIONS. The Fund has adopted the following restrictions which
cannot be changed without the approval of the holders of a majority of the
Fund's shares (which, as used in this SAI, means the lesser of (i) more than 50%
of the outstanding shares of the Trust (or a class or series, as applicable), or
(ii) 67% or more of the outstanding shares of the Trust (or a class or series,
as applicable) present at a meeting if holders of more than 50% of the
outstanding shares of the Trust (or a class or series, as applicable) are
represented at such meeting in person or by proxy):
 
The Fund may not:
 
    (1) borrow amounts in excess of 33 1/3% of its assets including amounts
  borrowed, and then only as a temporary measure for extraordinary or emergency
  purposes;
 
                                       11
<PAGE>   176
 
    (2) underwrite securities issued by other persons except insofar as the Fund
  may technically be deemed an underwriter under the Securities Act of 1933 in
  selling a portfolio security;
 
    (3) purchase or sell real estate (including limited partnership interests
  but excluding securities secured by real estate or interests therein and
  securities of companies, such as real estate investment trusts, which deal in
  real estate or interests therein), interests in oil, gas or mineral leases,
  commodities or commodity contracts (excluding options on securities, stock
  indexes and foreign currency ("Options"), Options on Futures Contracts and any
  other type of option, Futures Contracts and any other type of futures contract
  and Forward Contracts) in the ordinary course of its business. The Fund
  reserves the freedom of action to hold and to sell real estate, mineral
  leases, commodities or commodity contracts (including Options, Options on
  Futures Contracts, and any other type of option, Futures Contracts, any other
  type of futures contract and Forward Contracts) acquired as a result of the
  ownership of securities;
 
    (4) issue any senior securities except as permitted by the 1940 Act. For
  purposes of this restriction, collateral arrangements with respect to any type
  of option (including Options on Futures Contracts and Options), Forward
  Contracts and any type of futures contract (including Futures Contracts) and
  collateral arrangements with respect to initial and variation margin are not
  deemed to be the issuance of a senior security;
 
    (5) make loans to other persons. For these purposes the purchase of
  short-term commercial paper, the purchase of a portion or all of an issue of
  debt securities, the lending of portfolio securities, or the investment of the
  Fund's assets in repurchase agreements, shall not be considered the making of
  a loan; or
 
    (6) purchase any securities of an issuer of a particular industry, if as a
  result, more than 25% of its gross assets would be invested in securities of
  issuers whose principal business activities are in the same industry (except
  obligations issued or guaranteed by the U.S. Government or its agencies and
  instrumentalities and repurchase agreements collateralized by such
  obligations).
 
Except with respect to Investment Restriction (1) above and nonfundamental
investment policy (1) below, these investment restrictions and policies are
adhered to at the time of purchase or utilization of assets; a subsequent change
in circumstances will not be considered to result in a violation of policy.
 
In addition, the Fund has the following nonfundamental policies which may be
changed without shareholder approval. The Fund will not:
 
    (1) invest in illiquid investments, including securities subject to legal or
  contractual restrictions on resale or for which there is no readily available
  market (e.g., trading in the security is suspended, or, in the case of
  unlisted securities, where no market exists), unless the Board of Trustees has
  determined that such securities are liquid based on trading markets for the
  specific security, if more than 15% of the Fund's net assets (taken at market
  value) would be invested in such securities. Repurchase agreements maturing in
  more than seven days will be deemed to be illiquid for purposes of the Fund's
  limitation on investment in illiquid securities;
 
    (2) invest more than 5% of the value of the Fund's net assets, valued at the
  lower of cost or market, in warrants. Included within such amount, but not to
  exceed 2% of the value of the Fund's net assets, may be warrants which are not
  listed on the New York or American Stock Exchange. Warrants acquired by the
  Fund in units or attached to securities may be deemed to be without value:
 
    (3) invest for the purpose of exercising control or management;
 
   
    (4) purchase or retain securities of an issuer any of whose officers,
  directors, trustees or security holders is an officer or Trustee of the Fund,
  or is an officer or a director of the investment adviser of the Fund, if one
  or more of such persons also owns beneficially more than 0.5% of the
  securities of such issuer, and such persons owning more than 0.5% of such
  securities together own beneficially more than 5% of such securities;
    
 
   
    (5) purchase any securities or evidences of interest therein on margin,
  except that the Fund may obtain such short-term credit as may be necessary for
  the clearance of any transaction and except that the Fund may make margin
  deposits in connection with any type of option (including Options on Futures
  Contracts and options), any type of futures contract (including Futures
  Contracts), and Forward Contracts;
    
 
   
    (6) sell any security which the Fund does not own unless by virtue of its
  ownership of other securities the Fund has at the time of sale a right to
  obtain securities without payment of further consideration equivalent in kind
  and amount to the securities sold and provided that if such right is
  conditional, the sale is made upon the same conditions;
    
 
   
    (7) invest more than 5% of its gross assets in companies which, including
  predecessors, controlling persons, sponsoring entities, general partners and
  guarantors, have a record of less than three years' continuous operation or
  relevant business experience;
    
 
   
    (8) pledge, mortgage or hypothecate in excess of 33 1/2% of its gross
  assets. For purposes of this restriction, collateral arrangements with respect
  to any type of option, (including Options on Futures Contracts and Options),
  any type of futures contracts (including Futures Contracts), Forward Contracts
  and payments of initial and variation margin in connection therewith, are not
  considered a pledge of assets;
    
 
                                       12
<PAGE>   177
 
   
    (9) purchase or sell any put or call option or any combination thereof,
  provided that this shall not prevent (a) the purchase, ownership, holding or
  sale of (i) warrants where the grantor of the warrants is the issuer of the
  underlying securities or (ii) put or call options or combinations thereof with
  respect to securities, indexes of securities, foreign currency or futures
  contracts (including Futures Contracts) or (b) the purchase, ownership,
  holding or sale of contracts for the future delivery of securities or
  currencies; or
    
 
   
    (10) invest 25% or more of the market value of its total assets in
  securities of issuers in any one industry.
    
 
3. MANAGEMENT OF THE FUND
 
The Board of Trustees provides broad supervision over the affairs of the Fund.
The Adviser is responsible for the management of the Fund's assets, and the
officers of the Trust are responsible for the Fund's operations. The Trust's
officers and Trustees are listed below, together with their principal
occupations during the past five years. (Their titles may have varied during
that period.)
 
TRUSTEES
 
   
RICHARD B. BAILEY* (born 9/14/26)
    
Private Investor; Massachusetts Financial Services Company, former Chairman and
  Director (prior to September 30, 1991); Cambridge Bancorp, Director; Cambridge
  Trust Company, Director
 
PETER G. HARWOOD (born 4/3/26)
Private Investor
Address: 211 Lindsay Pond Road, Concord, Massachusetts
 
J. ATWOOD IVES (born 5/1/36)
   
Eastern Enterprises (diversified services company), Chairman, Trustee and Chief
  Executive Officer
    
Address: 9 Riverside Road, Weston, Massachusetts
 
LAWRENCE T. PERERA (born 6/23/35)
Hemenway & Barnes (attorneys), Partner
Address: 60 State Street, Boston, Massachusetts
 
WILLIAM J. POORVU (born 4/10/35)
Harvard University Graduate School of Business Administration, Adjunct
  Professor; CBL Associates Properties, Inc. (a real estate investment trust),
  Director; The Baupost Fund (a registered investment company), Vice Chairman
  (since November 1993), Chairman and Trustee (prior to November 1993)
Address: Harvard Business School, Soldier's Field Road, Cambridge, Massachusetts
 
CHARLES W. SCHMIDT (born 3/18/28)
   
Private Investor; International Technology Corporation, Director; Mohawk Paper
  Company, Director
    
Address: 30 Colpitts Road, Weston, Massachusetts
 
ARNOLD D. SCOTT* (born 12/16/42)
Massachusetts Financial Services Company, Senior Executive Vice President,
  Secretary and Director
 
JEFFREY L. SHAMES* (born 6/2/55)
   
Massachusetts Financial Services Company, Chairman and Chief Executive Officer
    
 
ELAINE R. SMITH (born 4/25/46)
   
Independent Consultant
    
Address: Weston, Massachusetts
 
DAVID B. STONE (born 9/2/27)
North American Management Corp. (investment adviser), Chairman and Director;
  Eastern Enterprises, Trustee
Address: Ten Post Office Square, Suite 300, Boston Massachusetts
 
OFFICERS
 
   
GEOFFREY L. KURINSKY,* Vice President (born 7/7/53)
    
Massachusetts Financial Services Company, Senior Vice President
 
W. THOMAS LONDON,* Treasurer (born 3/1/44)
Massachusetts Financial Services Company, Senior Vice President
 
STEPHEN E. CAVAN,* Secretary and Clerk (born 11/6/53)
Massachusetts Financial Services Company, Senior Vice President, General Counsel
  and Assistant Secretary
 
JAMES R. BORDEWICK, JR.,* Assistant Secretary (born 3/6/59)
Massachusetts Financial Services Company, Senior Vice President and Associate
  General Counsel
 
JAMES O. YOST,* Assistant Treasurer (born 6/12/60)
Massachusetts Financial Services Company, Vice President
 
MARK E. BRADLEY,* Assistant Treasurer (born 11/23/59)
Massachusetts Financial Services Company, Vice President (since March 1997);
  Putnam Investments, Vice President (from September 1994 until March 1997);
  Ernst & Young, Senior Tax Manager (prior to September 1994).
 
   
ELLEN MOYNIHAN,* Assistant Treasurer (born 11/13/57)
    
Massachusetts Financial Services Company, Vice President (since September 1996);
  Deloitte & Touche LLP, Senior Manager (prior to September 1996).
- ---------------
 
*"Interested persons" (as defined in the Investment Company Act of 1940, as
amended (the "1940 Act")) of the Adviser whose address is 500 Boylston Street,
Boston, Massachusetts 02116.
 
   
Each Trustee and officer holds comparable positions with certain affiliates of
MFS or with certain other funds of which MFS or a subsidiary of MFS is the
investment adviser or distributor. Messrs. Shames, Scott, and Cavan, are the
Chairman, a Director and the Secretary, respectively, of MFD, and hold similar
positions with certain other MFS affiliates. Mr. Bailey is a Director of Sun
Life Assurance Company of Canada (U.S.), a subsidiary of Sun Life Assurance
Company of Canada ("Sun Life").
    
 
The Fund pays the compensation of non-interested Trustees and Mr. Bailey (who
currently receive a fee of $1,000 per year plus $65 per meeting and $50 per
committee meeting attended, together with such Trustee's out-of-pocket expenses)
and has adopted a retirement plan for non-interested Trustees and Mr. Bailey.
Under the plan, a Trustee will retire upon reaching age 73 and if the Trustee
has completed at least five years of service, he would be entitled to annual
payments during his lifetime of up to 50% of such Trustee's average annual
compensation (based on the three years prior to his retirement) depending on his
length of service. A Trustee may also retire prior to age 73 and receive reduced
payments if he has completed at least five years of service. Under the plan, a
Trustee (or his beneficiaries) will also receive benefits for a period of time
in the event the Trustee is disabled or dies. These benefits will also be based
on the Trustee's average annual compensation and length of service. There is no
retirement plan provided by the Trust for
 
                                       13
<PAGE>   178
 
   
Messrs. Scott and Shames. The Fund will accrue its allocable share of
compensation expenses each year to cover current year's service and amortize
past service cost.
    
 
                           TRUSTEE COMPENSATION TABLE
 
   
<TABLE>
<CAPTION>
                                 RETIREMENT
                                  BENEFIT     ESTIMATED    TOTAL TRUSTEE
                       TRUSTEE   ACCRUED AS    CREDITED      FEES FROM
                        FEES      PART OF       YEARS        FUND AND
                        FROM        FUND          OF           FUND
       TRUSTEE         FUND(1)   EXPENSE(1)   SERVICE(2)    COMPLEX(3)
       -------         -------   ----------   ----------   -------------
<S>                    <C>       <C>          <C>          <C>
Richard B. Bailey....  $1,862       $307           6         $242,022
Peter G. Harwood.....   2,272        342           5          121,105
J. Atwood Ives.......   1,897        307          15          108,720
Lawrence T. Perera...   1,912        336          14          127,055
William Poorvu.......   2,077        339          14          121,105
Charles W. Schmidt...   1,882        338           7          121,105
Arnold D. Scott......       0          0         N/A                0
Jeffrey L. Shames....       0          0         N/A                0
Elaine R. Smith......   2,257        352          25          132,035
David B. Stone.......   2,277        357           7          127,055
</TABLE>
    
 
- ---------------
 
   
(1) For fiscal year ended August 31, 1998.
    
 
(2) Based on normal retirement age of 73. See the table below for the estimated
    annual benefits payable upon retirement by the Fund to a Trustee based on
    his or her estimated credited years of service.
 
   
(3) For calendar year 1997. All Trustees receiving compensation served as
    Trustees of 27 funds within the MFS fund complex (having aggregate net
    assets at December 31, 1997, of approximately $28.9 billion) except Mr.
    Bailey, who served as Trustee of 69 funds within the MFS fund complex
    (having aggregate net assets at December 31, 1997, of approximately $47.8
    billion).
    
 
          ESTIMATED ANNUAL BENEFITS PAYABLE BY FUND UPON RETIREMENT(4)
 
   
<TABLE>
<CAPTION>
                                    YEARS OF SERVICE
          AVERAGE         ------------------------------------
        TRUSTEE FEES       3         5         7    10 OR MORE
        ------------       -         -         -    ----------
        <S>               <C>       <C>       <C>   <C>
           $1,676         $251      $419      $587    $  838
            1,842          276       460       645       921
            2,007          301       502       703     1,004
            2,173          326       543       761     1,087
            2,339          351       585       819     1,169
            2,505          376       626       877     1,252
</TABLE>
    
 
- ---------------
 
(4) Other funds in the MFS fund complex provide similar retirement benefits to
    the Trustees.
 
   
As of October 30, 1998, the Trustees and officers as a group owned less than 1%
of the Fund's outstanding shares.
    
 
   
As of October 30, 1998, Sanwa Bank California, Cust. Wilshire Associates
Incorp., Attn. SFCBC-MZ3-2, 444 Market St., San Francisco, CA 94111-5325, was
the record owner of approximately 5.36% of the outstanding Class A shares of the
Fund.
    
 
   
As of October 30, 1998, Merrill Lynch, Pierce, Fenner & Smith Inc., 4800 Deer
Lake Drive East, Jacksonville, FL 32246, was the record owner of approximately
7.75% and 9.28% of the outstanding Class B and Class C shares, respectively, of
the Fund.
    
 
   
As of October 30, 1998, MFS Defined Contribution Plan, 500 Boylston Street,
Boston, MA 02116, was the record owner of approximately 99.99% of the
outstanding Class I shares.
    
 
The Declaration of Trust provides that the Trust will indemnify the Trustees and
officers against liabilities and expenses incurred in connection with litigation
in which they may be involved because of their offices with the Trust, unless,
as to liabilities to the Trust or its shareholders, it is finally adjudicated
that they engaged in willful misfeasance, bad faith, gross negligence or
reckless disregard of the duties involved in their offices, or with respect to
any matter unless it is adjudicated that they did not act in good faith in the
reasonable belief that their actions were in the best interest of the Trust. In
the case of a settlement, such indemnification will not be provided unless it
has been determined pursuant to the Declaration of Trust, that such officers or
Trustees have not engaged in willful misfeasance, bad faith, gross negligence or
reckless disregard of the duties involved in their offices.
 
INVESTMENT ADVISER
 
   
MFS and its predecessor organizations have a history of money management dating
from 1924. MFS is a subsidiary of Sun Life of Canada (U.S.) Financial Services
Holdings, Inc., which in turn is an indirect wholly owned subsidiary of Sun
Life.
    
 
   
The Adviser manages the Fund pursuant to an Investment Advisory Agreement, dated
October 20, 1993 (the "Advisory Agreement"). Under the Advisory Agreement, the
Adviser provides the Fund with overall investment advisory services. Subject to
such policies as the Trustees may determine, the Adviser makes investment
decisions for the Fund. For these services and facilities, the Adviser receives
a management fee, computed and paid monthly, equal to 0.75% of the average daily
net assets of the Fund on an annualized basis. For the Fund's fiscal years ended
August 31, 1998, August 31, 1997 and August 31, 1996, the Adviser received
investment advisory fees of $972,215, $868,526 and $755,233, respectively.
    
 
   
MFS pays the compensation of the Trust's officers and of any Trustee who is an
officer of MFS. The Adviser also furnishes at its own expense all necessary
administrative services, including office space, equipment, clerical personnel,
investment advisory facilities, and all executive and supervisory personnel
necessary for managing the Fund's investments, effecting its portfolio
transactions.
    
 
   
The Advisory Agreement will remain in effect until August 1, 1999, and will
continue in effect thereafter only if such continuance is specifically approved
at least annually by the Board of Trustees or by vote of a majority of the
Fund's outstanding voting securities (as defined under "Investment
Restrictions") and, in either case, by a majority of the Trustees who are not
parties to the Advisory Agreement or interested persons of any such party. The
Advisory Agreement terminates automatically if it is assigned and may be
terminated without penalty by vote of a majority of the Fund's shares (as
defined in "Investment Restrictions") or by either party on not more than 60
days' nor less than 30 days' written notice. MFS may render services to others
and that neither the Adviser nor its personnel shall be liable for any error of
judgment or mistake of law or for any loss arising out of any investment or for
any act or omission in the execution and management of the Fund, except for
willful misfeasance, bad faith or gross negligence in the performance of its or
their duties or by reason of reckless disregard of its or their obligations and
duties under the Advisory Agreement.
    
 
                                       14
<PAGE>   179
 
ADMINISTRATOR
 
   
MFS provides the Fund with certain financial, legal, compliance, shareholder
communications and other administrative services pursuant to a Master
Administrative Services Agreement dated March 1, 1997, as amended. Under the
Agreement, the Fund pays MFS an administrative fee up to 0.015% per annum of the
Fund's average daily net assets. This fee reimburses MFS for a portion of the
costs it incurs to provide such services. For the period from March 1, 1997
through August 31, 1997 and the fiscal year ended August 31, 1998, MFS received
fees under the Agreement of $8,511 and $18,411, respectively.
    
 
CUSTODIAN
 
State Street Bank and Trust Company (the "Custodian") is the custodian of the
Fund's assets. The Custodian's responsibilities include safekeeping and
controlling the Fund's cash and securities, handling the receipt and delivery of
securities, determining income and collecting interest and dividends on the
Fund's investments, maintaining books of original entry for portfolio and fund
accounting and other required books and accounts, and calculating the daily net
asset value of shares of each class of the Fund. The Custodian does not
determine the investment policies of the Fund or decide which securities the
Fund will buy or sell. The Fund may, however, invest in securities of the
Custodian and may deal with the Custodian as principal in securities
transactions. The Trustees have reviewed and approved as in the best interests
of the Fund and its shareholders subcustodial arrangements with The Chase
Manhattan Bank for securities of the Fund held outside the United States.
 
SHAREHOLDER SERVICING AGENT
 
   
MFS Service Center, Inc. (the "Shareholder Servicing Agent"), a wholly owned
subsidiary of MFS, is the Fund's shareholder servicing agent, pursuant to a
Shareholder Servicing Agreement, dated August 1, 1985 as amended (the "Agency
Agreement") with the Trust. The Shareholder Servicing Agent's responsibilities
under the Agency Agreement include administering and performing transfer agent
functions and keeping records in connection with the issuance, transfer and
redemption of each class of shares of the Fund. For these services, the
Shareholder Servicing Agent will receive a fee calculated as a percentage of the
average daily net assets of the Fund at an effective annual rate of 0.1125%. In
addition, the Shareholder Servicing Agent will be reimbursed by the Fund for
certain expenses incurred by the Shareholder Servicing Agent on behalf of the
Fund. State Street Bank and Trust Company, the dividend and distribution
disbursing agent of the Fund, has contracted with the Shareholder Servicing
Agent to administer and perform certain dividend and distribution disbursing
agent functions for the Fund.
    
 
DISTRIBUTOR
 
   
MFD, a wholly owned subsidiary of MFS, serves as distributor for the continuous
offering of shares of the Fund pursuant to a Distribution Agreement with the
Trust, dated January 1, 1995 (the "Distribution Agreement").
    
 
CLASS A SHARES: MFD acts as agent in selling Class A shares of the Fund to
dealers. The public offering price of Class A shares of the Fund is their net
asset value next computed after the sale plus a sales charge which varies based
upon the quantity purchased. The public offering price of a Class A share of the
Fund is calculated by dividing net asset value of a Class A share by the
difference (expressed as a decimal) between 100% and the sales charge percentage
of offering price applicable to the purchase (see "Purchases" in the
Prospectus). The sales charge scale set forth in the Prospectus applies to
purchases of Class A shares of the Fund alone or in combination with shares of
all classes of certain other funds in the MFS Family of Funds (the "MFS Funds")
and other funds (as noted under Right of Accumulation) by any person, including
members of a family unit (e.g., husband, wife and minor children) and bona fide
trustees, and also applies to purchases made under the Right of Accumulation or
a Letter of Intent (see "Investment and Withdrawal Programs" in this SAI). A
group might qualify to obtain quantity sales charge discounts (see "Investment
and Withdrawal Programs").
 
Class A shares of the Fund may be sold at their net asset value to certain
persons or in certain circumstances as described in the Prospectus. Such sales
are made without a sales charge to promote good will with employees and others
with whom MFS, MFD and/or the Fund have business relationships, and because the
sales effort, if any, involved in making such sales is negligible.
 
MFD allows discounts to dealers (which are alike for all dealers) from the
applicable public offering price of the Class A shares. Dealer allowances
expressed as a percentage of offering price for all offering prices are set
forth in the Prospectus (see "Purchases" in the Prospectus). The difference
between the total amount invested and the sum of (a) the net proceeds to the
Fund and (b) the dealer commission is the commission paid to the distributor.
Because of rounding in the computation of offering price, the portion of the
sales charge paid to the distributor may vary and the total sales charge may be
more or less than the sales charge calculated using the sales charge expressed
as a percentage of the offering price or as a percentage of the net amount
invested as listed in the Prospectus. In the case of the maximum sales charge,
the dealer retains 5% and MFD retains approximately 3/4 of 1% of the public
offering price. In addition, MFD, on behalf of the Fund, will pay a commission
to dealers who initiate and are responsible for purchases of $1 million or more
as described in the Prospectus.
 
CLASS B SHARES, CLASS C SHARES AND CLASS I SHARES: MFD acts as agent in selling
Class B, Class C and Class I shares of the Fund. The public offering price of
Class B, Class C and Class I shares is their net asset value next computed after
the sale (see "Purchases" in the Prospectus and the Prospectus Supplement
pursuant to which Class I Shares are offered).
 
GENERAL: Neither MFD nor dealers are permitted to delay the placement of orders
to benefit themselves by a price change. On occasion, MFD may obtain brokers
loans from various banks, including the Custodian for the MFS Funds, to
facilitate the
 
                                       15
<PAGE>   180
 
settlement of sales of shares of the Fund to dealers. MFD may benefit from its
temporary holding of funds paid to it by investment dealers for the purchase of
Fund shares.
 
   
During the Fund's fiscal year ended August 31, 1998, MFD and certain other
financial institutions received net commissions of $44,488 and $237,717,
respectively (as their concession on gross commissions of $282,205) for selling
Class A shares of the Fund. The Fund received $6,137,642, representing the
aggregate net asset value of such shares. During the Fund's fiscal year ended
August 31, 1997, MFD and certain other financial institutions received net
commissions of $23,709 and $160,236, respectively (as their concession on gross
sales charges of $183,945) for selling Class A shares of the Fund; the Fund
received $9,075,877, representing the aggregate net asset value of such shares.
During the Fund's fiscal year ended August 31, 1996, MFD and certain other
financial institutions received net commissions of $23,992 and $135,667,
respectively (as their concession on gross commissions of $159,659) for selling
Class A shares of the Fund. The Fund received $10,258,374, representing the
aggregate net asset value of such shares.
    
 
   
During the Fund's fiscal year ended August 31, 1998, the CDSC imposed on
redemption of Class A, Class B and C shares was $3,036, $109,015 and $3,111,
respectively. During the Fund's fiscal year ended August 31, 1997, the CDSC
imposed on redemption of Class A, Class B and Class C shares was $304, $140,576
and $3,156, respectively. During the Fund's fiscal year ended August 31, 1996,
the CDSC imposed on redemption of Class A, Class B and Class C shares was
$1,116, $106,267 and $346, respectively.
    
 
   
The Distribution Agreement will remain in effect until August 1, 1999, and will
continue in effect thereafter only if such continuance is specifically approved
at least annually by the Board of Trustees or by vote of a majority of the
Trust's shares (as defined in "Investment Restrictions") and, in either case, by
a majority of the Trustees who are not parties to the Distribution Agreement or
interested persons of any such party. The Distribution Agreement terminates
automatically if it is assigned and may be terminated without penalty by either
party on not more than 60 days' nor less than 30 days' notice.
    
 
4. PORTFOLIO TRANSACTIONS AND BROKERAGE COMMISSIONS
 
Specific decisions to purchase or sell securities for the Fund are made by
person's affiliated with the Adviser. Any such person may serve other clients of
the Adviser or any subsidiary of the Adviser in similar capacities. Changes in
the Fund's investments are reviewed by the Board of Trustees.
 
The primary consideration in placing portfolio security transactions with
broker-dealers for execution is to obtain and maintain the availability of
execution at the most favorable prices and in the most effective manner
possible. The Adviser attempts to achieve this result by selecting
broker-dealers to execute portfolio transactions on behalf of the Fund and other
clients of the Adviser on the basis of their professional capability, the value
and quality of their brokerage services, and the general level of their
brokerage commissions. In the case of securities traded in the over-the-counter
market (where no stated commissions are paid but the prices include a dealer's
markup or markdown), the Adviser normally seeks to deal directly with the
primary market-makers, unless, in its opinion, best execution is available
elsewhere. In the case of securities purchased from underwriters, the cost of
such securities generally includes a fixed underwriting commission or
concession. From time to time, soliciting dealer fees are available to the
Adviser on the tender of the Fund's portfolio securities in so-called tender or
exchange offers. Such soliciting dealer fees are in effect recaptured for the
Fund by the Adviser. At present no other recapture arrangements are in effect.
 
Consistent with the foregoing primary consideration, the Conduct Rules of the
NASD and such other policies as the Trustees may determine, the Adviser may
consider sales of shares of the Fund and of other investment company clients of
MFD as a factor in the selection of broker-dealers to execute the Fund's
portfolio transactions.
 
Under the Advisory Agreement and as permitted by Section 28(e) of the Securities
Exchange Act of 1934, the Adviser may cause the Fund to pay a broker-dealer
which provides brokerage and research services to the Adviser an amount of
commission for effecting a securities transaction for the Fund in excess of the
amount other broker-dealers would have charged for the transaction if the
Adviser determines in good faith that the greater commission is reasonable in
relation to the value of the brokerage and research services provided by the
executing broker-dealer viewed in terms of either a particular transaction or
the Adviser's overall responsibilities to the Fund or to its other clients. Not
all of such services are useful or of value in advising the Fund.
 
The term "brokerage and research services" includes: advice as to the value of
securities, the advisability of investing in, purchasing, or selling securities,
and the availability of securities or of purchasers or sellers of securities;
furnishing analyses and reports concerning issues, industries, securities,
economic factors and trends, portfolio strategy and the performance of accounts;
and effecting securities transactions and performing functions incidental
thereto such as clearance and settlement.
 
Although commissions paid on every transaction will, in the judgment of the
Adviser, be reasonable in relation to the value of the brokerage services
provided, commissions exceeding those which another broker might charge may be
paid to broker-dealers who were selected to execute transactions on behalf of
the Fund and the Adviser's other clients in part for providing advice as to the
availability of securities or of purchasers or sellers of securities and
services in effecting securities transactions and performing functions
incidental thereto such as clearance and settlement.
 
Broker-dealers may be willing to furnish statistical, research and other factual
information or services ("Research") to the Adviser for no consideration other
than brokerage or underwrit-
 
                                       16
<PAGE>   181
 
   
ing commissions. Securities may be bought or sold from time to time through such
broker-dealers on behalf of the Fund. The Fund's Trustees (together with the
Trustees of the other MFS Funds) have directed the Adviser to allocate a total
of $54,160 of commission business from the MFS Funds to the Pershing Division of
Donaldson, Lufkin & Jenrette as consideration for the annual renewal of certain
publications provided by Lipper Analytical Securities Corporation (which
provides information useful to the Trustees in reviewing the relationship
between the Fund and the Adviser).
    
 
The Adviser's investment management personnel attempt to evaluate the quality of
Research provided by brokers. The Adviser sometimes uses evaluations resulting
from this effort as a consideration in the selection of brokers to execute
portfolio transactions. However, the Adviser is unable to quantify the amount of
commissions set forth below which were paid as a result of such Research because
a substantial number of transactions were effected through brokers which provide
Research but which were selected principally because of their execution
capabilities.
 
The management fee that the Fund pays to the Adviser will not be reduced as a
consequence of the Adviser's receipt of brokerage and research services. To the
extent the Fund's portfolio transactions are used to obtain such services, the
brokerage commissions paid by the Fund will exceed those that might otherwise be
paid by an amount which cannot be presently determined. Such services would be
useful and of value to the Adviser in serving both the Fund and other clients
and, conversely, such services obtained by the placement of brokerage business
of other clients would be useful to the Adviser in carrying out its obligations
to the Fund. While such services are not expected to reduce the expenses of the
Adviser, the Adviser would, through use of the services, avoid the additional
expenses which would be incurred if it should attempt to develop comparable
information through its own staff.
 
   
For the Fund's fiscal year ended August 31, 1998, the Fund paid brokerage
commissions of $326,715 on total transactions of $421,564,572. For the Fund's
fiscal year ended August 31, 1997, the Fund paid brokerage commissions of
$325,249 on total transactions of $151,828,905. For the Fund's fiscal year ended
August 31, 1996, the Fund paid brokerage commissions of $266,365 on total
transactions of $118,653,749.
    
 
   
During the fiscal years ended August 31, 1998, 1997 and 1996, the Fund did not
acquire or own securities issued by broker-dealers of this Fund.
    
 
In certain instances there may be securities which are suitable for the Fund's
portfolio as well as for that of one or more of the other clients of the Adviser
or any subsidiary of the Adviser. Investment decisions for the Fund and for such
other clients are made with a view to achieving their respective investment
objectives. It may develop that a particular security is bought or sold for only
one client even though it might be held by, or bought or sold for, other
clients. Likewise, a particular security may be bought for one or more clients
when one or more other clients are selling that same security. Some simultaneous
transactions are inevitable when several clients receive investment advice from
the same investment adviser, particularly when the same security is suitable for
the investment objectives of more than one client. When two or more clients are
simultaneously engaged in the purchase or sale of the same security, the
securities are allocated among clients in a manner believed by the Adviser to be
equitable to each. It is recognized that in some cases this system could have a
detrimental effect on the price or volume of the security as far as the Fund is
concerned. In other cases, however, the Fund believes that its ability to
participate in volume transactions will produce better executions for the Fund.
 
5. SHAREHOLDER SERVICES
 
INVESTMENT AND WITHDRAWAL PROGRAMS -- The Fund makes available the following
programs designed to enable shareholders to add to their investment or withdraw
from it with a minimum of paper work. These are described below and, in certain
cases, in the Prospectus. The programs involve no extra charge to shareholders
(other than a sales charge in the case of certain Class A share purchases) and
may be changed or discontinued at any time by a shareholder or the Fund.
 
LETTER OF INTENT: If a shareholder (other than a group purchaser described
below) anticipates purchasing $50,000 or more of Class A shares of the Fund
alone or in combination with all classes of shares of other MFS Funds or MFS
Fixed Fund (a bank collective investment fund) within a 13-month period (or
36-month period in the case of purchases of $1 million or more), the shareholder
may obtain Class A shares of the Fund at the same reduced sales charge as though
the total quantity were invested in one lump sum by completing the Letter of
Intent section of the Fund's Account Application or filing a separate Letter of
Intent application (available from the Shareholder Servicing Agent) within 90
days of the commencement of purchases. Subject to acceptance by MFD and the
conditions mentioned below, each purchase will be made at a public offering
price applicable to a single transaction of the dollar amount specified in the
Letter of Intent application. The shareholder or his dealer must inform MFD that
the Letter of Intent is in effect each time shares are purchased. The
shareholder makes no commitment to purchase additional shares, but if his
purchases within 13 months (or 36-months in the case of purchases of $1 million
or more) plus the value of shares credited toward completion of the Letter of
Intent do not total the sum specified, he will pay the increased amount of the
sales charge as described below. Instructions for issuance of shares in the name
of a person other than the person signing the Letter of Intent application must
be accompanied by a written statement from the dealer stating that the shares
were paid for by the person signing such Letter. Neither income dividends nor
capital gain distributions taken in additional shares will apply toward the
completion of the Letter of Intent. Dividends and distributions of other MFS
Funds automatically reinvested in shares of the Fund pursuant to the
Distribution Investment Program will also not apply toward completion of the
Letter of Intent.
                                       17
<PAGE>   182
 
Out of the shareholder's initial purchase (or subsequent purchases if
necessary), 5% of the dollar amount specified in the Letter of Intent
application shall be held in escrow by the Shareholder Servicing Agent in the
form of shares registered in the shareholder's name. All income dividends and
capital gain distributions on escrowed shares will be paid to the shareholder or
to his order. When the minimum investment so specified is completed (either
prior to or by the end of the 13-month period or 36-month period, as
applicable), the shareholder will be notified and the escrowed shares will be
released.
 
If the intended investment is not completed, the Shareholder Servicing Agent
will redeem an appropriate number of the escrowed shares in order to realize
such difference. Shares remaining after any such redemption will be released by
the Shareholder Servicing Agent. By completing and signing the Account
Application or separate Letter of Intent application, the shareholder
irrevocably appoints the Shareholder Servicing Agent his attorney to surrender
for redemption any or all escrowed shares with full power of substitution in the
premises.
 
RIGHT OF ACCUMULATION: A shareholder qualifies for cumulative quantity discounts
on the purchase of Class A shares when that shareholder's new investment,
together with the current offering price value of all the holdings of Class A,
Class B and Class C shares of that shareholder in the MFS Funds and MFS Fixed
Fund (a bank collective investment fund) reaches a discount level (see
"Purchases" in the Prospectus for the sales charges on quantity purchases). For
example, if a shareholder owns shares valued at $37,500 and purchases an
additional $12,500 of Class A shares of the Fund, the sales charge for the
$12,500 purchase would be at the rate of 4.75% (the rate applicable to single
transactions of $50,000). A shareholder must provide the Shareholder Servicing
Agent (or his investment dealer must provide MFD) with information to verify
that the quantity sales charge discount is applicable at the time the investment
is made.
 
SUBSEQUENT INVESTMENT BY TELEPHONE: Each shareholder may purchase additional
shares of any MFS Fund by telephoning the Shareholder Servicing Agent toll-free
at (800) 225-2606. The minimum purchase amount is $50 and the maximum purchase
amount is $100,000. Shareholders wishing to avail themselves of this telephone
purchase privilege must so elect on their Account Application and designate
thereon a bank and account number from which purchases will be made. If a
telephone purchase request is received by the Shareholder Servicing Agent on any
business day prior to the close of regular trading on the Exchange (generally,
4:00 p.m., Eastern time), the purchase will occur at the closing net asset value
of the shares purchased on that day. The Shareholder Servicing Agent may be
liable for any losses resulting from unauthorized telephone transactions if it
does not follow reasonable procedures designed to verify the identity of the
caller. The Shareholder Servicing Agent will request personal or other
information from the caller, and will normally also record calls. Shareholders
should verify the accuracy of confirmation statements immediately after their
receipt.
 
DISTRIBUTION INVESTMENT PROGRAM: Distributions of dividends and capital gains
made by the Fund with respect to a particular class of shares may be
automatically invested in shares of the same class of one of the other MFS
Funds, if shares of the fund are available for sale. Such investments will be
subject to additional purchase minimums. Distributions will be invested at net
asset value (exclusive of any sales charge) and will not be subject to any CDSC.
Distributions will be invested at the close of business on the payable date for
the distribution. A shareholder considering the Distribution Investment Program
should obtain and read the prospectus of the other fund and consider the
differences in objectives and policies before making any investment.
 
SYSTEMATIC WITHDRAWAL PLAN: A shareholder may direct the Shareholder Servicing
Agent to send him (or anyone he designates) regular periodic payments based upon
the value of his account. Each payment under a Systematic Withdrawal Plan (a
"SWP") must be at least $100, except in certain limited circumstances. The
aggregate withdrawals of Class B shares in any year pursuant to a SWP generally
are limited to 10% of the value of the account at the time of the establishment
of the SWP. SWP payments are drawn from the proceeds of share redemptions (which
would be a return of principal and, if reflecting a gain, would be taxable).
Redemptions of Class B and Class C shares will be made in the following order:
(i) any "Free Amount"; (ii) to the extent necessary, any "Reinvested Shares";
and (iii) to the extent necessary, the "Direct Purchase" subject to the lowest
CDSC (as such terms are defined in "Contingent Deferred Sales Charge" in the
Prospectus). The CDSC will be waived in the case of redemptions of Class B and
Class C shares pursuant to a SWP, but will not be waived in the case of SWP
redemptions of Class A shares which are subject to a CDSC. To the extent that
redemptions for such periodic withdrawals exceed dividend income reinvested in
the account, such redemptions will reduce and may eventually exhaust the number
of shares in the shareholder's account. All dividend and capital gain
distributions for an account with a SWP will be reinvested in full and
fractional shares of the Fund at the net asset value in effect at the close of
business on the record date for such distributions. To initiate this service,
shares having an aggregate value of at least $5,000 either must be held on
deposit by, or certificates for such shares must be deposited with, the
Shareholder Servicing Agent. With respect to Class A shares, maintaining a
withdrawal plan concurrently with an investment program would be disadvantageous
because of the sales charges included in share purchases and the imposition of a
CDSC on certain redemptions. The shareholder may deposit into the account
additional shares of the Fund, change the payee or change the dollar amount of
each payment. The Shareholder Servicing Agent may charge the account for
services rendered and expenses incurred beyond those normally assumed by the
Fund with respect to the liquidation of shares. No charge is currently assessed
against the account, but one could be instituted by the Shareholder Servicing
Agent on 60 days' notice in writing to the shareholder in the event that the
Fund ceases to assume the cost of these services. The Fund may terminate any SWP
for an account if the value of the account falls below
 
                                       18
<PAGE>   183
 
$5,000 as a result of share redemptions (other than as a result of a SWP) or an
exchange of shares of the Fund for shares of another MFS Fund. Any SWP may also
be terminated at any time by either the shareholder or the Fund.
 
INVEST BY MAIL: Additional investments of $50 or more may be made at any time by
mailing a check payable to the Fund directly to the Shareholder Servicing Agent.
The shareholder's account number and the name of his investment dealer must be
included with each investment.
 
GROUP PURCHASES: A bona fide group and all of its members may be treated as a
single purchaser and, under the Right of Accumulation (but not a Letter of
Intent), obtain quantity sales charge discounts on the purchase of Class A
shares if the group (1) gives its endorsement or authorization to the investment
program so it may be used by the investment dealer to facilitate solicitation of
the membership, thus effecting economies of sales effort; (2) has been in
existence for at least six months and has a legitimate purpose other than to
purchase mutual fund shares at a discount; (3) is not a group of individuals
whose sole organizational nexus is as credit cardholders of a company,
policyholders of an insurance company, customers of a bank or broker-dealer,
clients of an investment adviser or other similar groups; and (4) agrees to
provide certification of membership of those members investing money in the MFS
Funds upon the request of MFD.
 
AUTOMATIC EXCHANGE PLAN: Shareholders having account balances of at least $5,000
in any MFS Fund may exchange their shares for the same class of shares of other
MFS Funds (if available for sale) under the Automatic Exchange Plan. The
Automatic Exchange Plan provides for automatic exchanges of funds from the
shareholder's account in a MFS Fund for investment in other MFS Funds selected
by the shareholder. Under the Automatic Exchange Plan, exchanges of at least $50
each may be made to up to six different funds effective on the seventh day of
each month or of every third month, depending whether monthly or quarterly
exchanges are elected by the shareholder. If the seventh day of the month is not
a business day, the transaction will be processed on the next business day.
Generally, the initial exchange will occur after receipt and processing by the
Shareholder Servicing Agent of an application in good order. Exchanges will
continue to be made from a shareholder's account in any MFS Fund, as long as the
balance of the account is sufficient to complete the exchanges. Additional
payments made to a shareholder's account in such MFS Fund will extend the period
that exchanges will continue to be made under the Automatic Exchange Plan.
However, if additional payments are added to an account subject to the Automatic
Exchange Plan shortly before an exchange is scheduled, such funds may not be
available for exchanges until the following month; therefore, care should be
used to avoid inadvertently terminating the Automatic Exchange Plan through
exhaustion of the account balance.
 
No transaction fee for exchanges will be charged in connection with the
Automatic Exchange Plan. However, exchanges of shares of MFS Money Market Fund,
MFS Government Money Market Fund and Class A shares of MFS Cash Reserve Fund
will be subject to any applicable sales charge. Changes in amounts to be
exchanged to each fund, the funds to which exchanges are to be made and the
timing of exchanges (monthly or quarterly), or termination of a shareholder's
participation in the Automatic Exchange Plan will be made after instructions in
writing or by telephone (an "Exchange Change Request") are received by the
Shareholder Servicing Agent in proper form (i.e., if in writing -- signed by the
record owner(s) exactly as shares of the MFS Fund are registered; if by
telephone -- proper account identification is given by the dealer or shareholder
of record). Each Exchange Change Request (other than termination of
participation in the program) must involve at least $50. Generally, if an
Exchange Change Request is received before the close of business on the last
business day of a month, the Exchange Change Request will be effective for the
following month's exchange.
 
A shareholder's right to make additional investments in any of the MFS Funds, to
make exchanges of shares from one MFS Fund to another and to withdraw from an
MFS Fund, as well as a shareholder's other rights and privileges, are not
affected by a shareholder's participation in the Automatic Exchange Plan.
 
The Automatic Exchange Plan is part of the Exchange Privilege. For additional
information regarding the Automatic Exchange Plan including the treatment of any
CDSC, see "Exchange Privilege" below.
 
REINSTATEMENT PRIVILEGE: Shareholders of the Fund and shareholders of the other
MFS Funds (except MFS Money Market Fund, MFS Government Money Market Fund and
holders of Class A shares of MFS Cash Reserve Fund in the case where the shares
of such funds are acquired through direct purchase or reinvested dividends) who
have redeemed their shares have a one-time right to reinvest the redemption
proceeds in the same class of shares of any of the MFS Funds (if shares of the
fund are available for sale) at net asset value (without a sales charge) and, if
applicable, with credit for any CDSC paid. In the case of proceeds reinvested in
shares of MFS Money Market Fund, MFS Government Money Market Fund and Class A
shares of MFS Cash Reserve Fund, the shareholder has the right to exchange the
acquired shares for shares of another MFS Fund at net asset value pursuant to
the exchange privilege described below. Such a reinvestment must be made within
90 days of the redemption and is limited to the amount of the redemption
proceeds. If the shares credited for any CDSC paid are then redeemed within six
years of their initial purchase in the case of Class B shares or within 12
months of the initial purchase of Class C shares and certain Class A shares, a
CDSC will be imposed upon redemption. Although redemptions and repurchases of
shares are taxable events, a reinvestment within a certain period of time in the
same fund may be considered a "wash sale" and may result in the inability to
recognize currently any loss realized on the original redemption for federal
income tax purposes. Please see your tax adviser for further information.
 
EXCHANGE PRIVILEGE -- Subject to the requirements set forth below, some or all
of the shares for which payment has been received by the Fund (i.e., an
established account) may be
 
                                       19
<PAGE>   184
 
exchanged for shares of the same class of any of the other MFS Funds (if
available for sale and if the purchaser is eligible to purchase the class of
shares) at net asset value. Exchanges will be made only after instructions in
writing or by telephone (an "Exchange Request") are received for an established
account by the Shareholder Servicing Agent.
 
Each Exchange Request must be in proper form (i.e., if in writing -- signed by
the record owner(s) exactly as the shares are registered; if by
telephone -- proper account identification is given by the dealer or shareholder
of record) and each exchange must involve either shares having an aggregate
value of at least $1,000 ($50 in the case of retirement plan participants whose
sponsoring organizations subscribe to the MFS FUNDamental 401(k) Plan or another
similar 401(k) recordkeeping system made available by MFS Service Center, Inc.)
or all the shares in the account. Each exchange involves the redemption of the
shares of the Fund to be exchanged and the purchase at net asset value (i.e.,
without a sales charge) of shares of the same class of the other MFS Fund. Any
gain or loss on the redemption of the shares exchanged is reportable on the
shareholder's federal income tax return, unless both the shares received and the
shares surrendered in the exchange are held in a tax-deferred retirement plan or
other tax-exempt account. No more than five exchanges may be made in any one
Exchange Request by telephone. If the Exchange Request is received by the
Shareholder Servicing Agent prior to the close of regular trading on the
Exchange, the exchange usually will occur on that day if all of the requirements
set forth above have been complied with at that time. However, payment of the
redemption proceeds by the Fund, and thus purchase of shares of the other MFS
Fund, may be delayed for up to seven days if the Fund determines that such a
delay would be in the best interest of all its shareholders. Investment dealers
which have satisfied criteria established by MFD may also communicate a
shareholder's Exchange Request to MFD by facsimile subject to the requirements
set forth above.
 
No CDSC is imposed on exchanges among the MFS Funds, although liability for the
CDSC is carried forward to the exchanged shares. For purposes of calculating the
CDSC upon redemption of shares acquired in an exchange, the purchase of shares
acquired in one or more exchanges is deemed to have occurred at the time of the
original purchase of the exchanged shares.
 
Additional information with respect to any of the MFS Funds, including a copy of
its current prospectus, may be obtained from investment dealers or the
Shareholder Servicing Agent. A shareholder considering an exchange should obtain
and read the prospectus of the other MFS Fund and consider the differences in
objectives and policies before making any exchange. Shareholders in the other
MFS Funds (except holders of shares of MFS Money Market Fund, MFS Government
Money Market Fund and Class A shares of MFS Cash Reserve Fund acquired through
direct purchase and dividends reinvested prior to June 1, 1992) have the right
to exchange their shares for shares of the MFS Funds, subject to the conditions,
if any, set forth in their respective prospectuses. In addition, unitholders of
the MFS Fixed Fund (a bank collective investment fund) have the right to
exchange their units (except units acquired through direct purchases) for shares
of the Fund, subject to the conditions, if any, imposed upon such unitholders by
the MFS Fixed Fund.
 
Any state income tax advantages for investment in shares of each state-specific
series of MFS Municipal Series Trust may only benefit residents of such states.
Investors should consult their own tax advisers to be sure this is an
appropriate investment, based on their residency and each state's income tax
laws.
 
The exchange privilege (or any aspect of it) may be changed or discontinued and
is subject to certain limitations (see "Purchases" in the Prospectus).
 
   
TAX-DEFERRED RETIREMENT PLANS -- Shares of the Fund may be purchased by all
types of tax-deferred retirement plans. MFD makes available, through investment
dealers, plans and/or custody agreements, the following:
    
 
   
  Traditional Individual Retirement Accounts (IRAs) (for individuals who desire
  to make limited contributions to a tax-deferred retirement program and, if
  eligible, to receive a federal income tax deduction for amounts contributed);
    
 
   
  Roth Individual Retirement Accounts (Roth IRAs) (for individuals who desire to
  make limited contributions to a tax-favored retirement program);
    
 
  Simplified Employee Pension (SEP-IRA) Plans;
 
  Retirement Plans Qualified under Section 401(k) of the Code;
 
  403(b) Plans (deferred compensation arrangements for employees of public
  school systems and certain non-profit organizations); and
 
  Certain other qualified pension and profit-sharing plans.
 
The plan documents provided by MFD designate a trustee or custodian (unless
another trustee or custodian is designated by the individual or group
establishing the plan) and contain specific information about the plans. Each
plan provides that dividends and distributions will be reinvested automatically.
For further details with respect to any plan, including fees charged by the
trustee, custodian or MFD, tax consequences and redemption information, see the
specific documents for that plan. Plan documents other than those provided by
MFD may be used to establish any of the plans described above. Third party
administrative services, available for some corporate plans, may limit or delay
the processing of transactions.
 
Investors should consult with their tax adviser before establishing any of the
tax-deferred retirement plans described above.
 
6. TAX STATUS
 
The Fund has elected to be treated and intends to qualify each year as a
"regulated investment company" under Subchapter M of the Code by meeting all
applicable requirements of Subchapter M, including requirements as to the nature
of the Fund's gross income, the amount of Fund distributions, and the
composition of the Fund's portfolio assets. Because the Fund intends to
distribute all of its net investment income and net realized
 
                                       20
<PAGE>   185
 
capital gains to shareholders in accordance with the timing requirements imposed
by the Code, it is not expected that the Fund will be required to pay any
federal income or excise taxes, although the Fund's foreign-source income may be
subject to foreign withholding taxes. If the Fund should fail to qualify as a
"regulated investment company" in any year, the Fund would incur a regular
corporate federal income tax upon its taxable income and Fund distributions
would generally be taxable as ordinary dividend income to shareholders.
 
   
Shareholders of the Fund normally will have to pay federal income taxes, and any
state or local taxes, on the dividends and capital gain distributions they
receive from the Fund. Dividends from ordinary income and any distributions from
net short-term capital gains are taxable to shareholders as ordinary income for
federal income tax purposes, whether the distributions are paid in cash or
reinvested in additional shares. A portion of the Fund's ordinary income
dividends is normally eligible for the dividends received deduction for
corporations if the recipient otherwise qualifies for that deduction with
respect to its holding of Fund shares. Availability of the deduction for
particular corporate shareholders is subject to certain limitations, and
deducted amounts may be subject to the alternative minimum tax and may result in
certain basis adjustments. Distributions of net capital gains (i.e., the excess
of net long-term capital gains over net short-term capital losses), whether paid
in cash or reinvested in additional shares, are taxable to shareholders as
long-term capital gains for federal income tax purposes without regard to the
length of time the shareholders have held their shares. Any Fund dividend that
is declared in October, November, or December of any calendar year, that is
payable to shareholders of record in such a month, and that is paid the
following January will be treated as if received by the shareholders on December
31 of the year in which the dividend is declared. The Fund will notify
shareholders regarding the federal tax status of its distributions after the end
of each calendar year.
    
 
Any Fund distribution will have the effect of reducing the per share net asset
value of shares in the Fund by the amount of the distribution. Shareholders
purchasing shares shortly before the record date of any distribution may thus
pay the full price for the shares and then effectively receive a portion of the
purchase price back as a taxable distribution.
 
   
In general, any gain or loss realized upon a taxable disposition of shares of
the Fund by a shareholder that holds such shares as a capital asset will be
treated as a long-term capital gain or loss if the shares have been held for
more than twelve months and otherwise as a short-term capital gain or loss.
However, any loss realized upon a disposition of shares in the Fund held for six
months or less will be treated as a long-term capital loss to the extent of any
distributions of net capital gain made with respect to those shares. Any loss
realized upon a disposition of shares may also be disallowed under rules
relating to wash sales. Gain may be increased (or loss reduced) upon a
redemption of Class A shares of the Fund within ninety days after their purchase
followed by any purchase (including purchases by exchange or by reinvestment)
without payment of an additional sales charge of Class A shares of the Fund or
of another MFS Fund (or any shares of an MFS Fund generally sold subject to a
sales charge).
    
 
The Fund's current dividend and accounting policies will affect the amount,
timing and character of distributions to shareholders and may, under certain
circumstances, make an economic return of capital taxable to shareholders. Any
investment in zero coupon bonds, deferred interest bonds, payment-in-kind bonds
and certain securities purchased at a market discount will cause the Fund to
recognize income prior to the receipt of cash payments with respect to those
securities. In order to distribute this income and avoid a tax on the Fund, the
Fund may be required to liquidate portfolio securities that it might otherwise
have continued to hold, potentially resulting in additional taxable gain or loss
to the Fund.
 
   
The Fund's transactions in options, Futures Contracts, and Forward Contracts,
will be subject to special tax rules that may affect the amount, timing, and
character of Fund income and distributions to shareholders. For example, certain
positions held by the Fund on the last business day of each taxable year will be
marked to market (i.e., treated as if closed out) on that day, and any gain or
loss associated with the positions will be treated as 60% long-term and 40%
short-term capital gain or loss. Certain positions held by the Fund that
substantially diminish its risk of loss with respect to other positions in its
portfolio may constitute "straddles," and may be subject to special tax rules
that would cause deferral of Fund losses, adjustments in the holding periods of
Fund securities, and conversion of short-term into long-term capital losses.
Certain tax elections exist for straddles that may alter the effects of these
rules. The Fund will limit its activities in options, Futures Contracts, and
Forward Contracts to the extent necessary to meet the requirements of Subchapter
M of the Code.
    
 
Special tax considerations apply with respect to foreign investments of the
Fund. Foreign exchange gains and losses realized by the Fund will generally be
treated as ordinary income and losses. The use of foreign currencies for
non-hedging purposes and investment by the Fund in certain "passive foreign
investment companies" may be limited in order to avoid taxes on the Fund. The
Fund may elect to mark to market any investments in "passive foreign investment
companies" on the last day of each taxable year. This election may cause the
Fund to recognize income prior to the receipt of cash payments with respect to
those investments; in order to distribute this income and avoid a tax on the
Fund, the Fund may be required to liquidate portfolio securities that it might
otherwise have continued to hold.
 
   
Investment income received by the Fund from foreign securities may be subject to
foreign income taxes withheld at the source; the Fund does not expect to be able
to pass through to shareholders foreign tax credits with respect to such foreign
taxes. The United States has entered into tax treaties with many foreign
countries that may entitle the Fund to a reduced rate of tax or an exemption
from tax on such income; the Fund intends to qualify for treaty reduced rates
where available. It is not possible, however, to determine the Fund's effective
rate of foreign tax in advance since the amount of the Fund's assets to be
invested within various countries is not known.
    
                                       21
<PAGE>   186
 
   
Dividends and certain other payments to persons who are not citizens or
residents of the United States or U.S. entities ("Non-U.S. Persons") are
generally subject to U.S. tax withholding at the rate of 30%. The Fund intends
to withhold U.S. federal income tax at the rate of 30% (or any lower rate
permitted under an applicable treaty) on taxable dividends and other payments to
Non-U.S. Persons that are subject to such withholding. Any amounts overwithheld
may be recovered by such persons by filing a claim for refund with the U.S.
Internal Revenue Service within the time period appropriate to such claims.
Distributions received from the Fund by Non-U.S. Persons may also be subject to
tax under the laws of their own jurisdictions. The Fund is also required in
certain circumstances to apply backup withholding at the rate of 31% on taxable
dividends and redemption proceeds paid to any shareholder (including a Non-U.S.
Person) who does not furnish to the Fund certain information and certifications
or who is otherwise subject to backup withholding. Backup withholding will not,
however, be applied to payments that have been subject to 30% withholding.
    
 
As long as it qualifies as a regulated investment company under the Code, the
Fund will not be required to pay any Massachusetts income or excise taxes.
 
7. DETERMINATION OF NET ASSET VALUE AND PERFORMANCE
 
NET ASSET VALUE
 
The net asset value per share of each class of the Fund is determined each day
during which the Exchange is open for trading. (As of the date of this SAI, the
Exchange is open for trading every weekday except for the following holidays or
the day on which they are observed: New Year's Day, Martin Luther King, Jr.,
Day, Presidents' Day, Good Friday, Memorial Day, Independence Day, Labor Day,
Thanksgiving Day and Christmas Day.) This determination is made once each day as
of the close of regular trading on the Exchange by deducting the amount of the
liabilities attributable to the class from the value of the assets attributable
to the class and dividing the difference by the number of shares of the class
outstanding.
 
Bonds and other fixed income securities (other than short-term obligations) in
the Fund's portfolio are valued on the basis of valuations furnished by a
pricing service which utilizes both dealer-supplied valuations and electronic
data processing techniques which take into account appropriate factors such as
institution-size trading in similar groups of securities, yield, quality, coupon
rate, maturity, type of issue, trading characteristics and other market data,
without exclusive reliance upon exchange or over-the-counter prices, since such
valuations are believed to reflect more accurately the fair value of such
securities. Forward Contracts will be valued using a pricing model taking into
consideration market data from an external pricing source. Use of the pricing
service has been approved by the Trust's Board of Trustees. All other
securities, futures contracts and options in the Fund's portfolio (other than
short-term obligations) for which the principal market is one or more securities
or commodities exchanges (whether domestic or foreign) will be valued at the
last reported sale price or at the settlement price prior to the determination
(or if there has been no current sale, at the closing bid price) on the primary
exchange on which such securities, futures contracts or options are traded; but
if a securities exchange is not the principal market for securities, such
securities will, if market quotations are readily available, be valued at
current bid prices, unless such securities are reported on the Nasdaq stock
market, in which case they are valued at the last sale price or, if no sales
occurred during the day, at the last quoted bid price. Short-term obligations
with a remaining maturity in excess of 60 days will be valued based upon dealer
supplied valuations. Short-term obligations with a remaining maturity in excess
of 60 days will be valued upon dealer supplied valuations. Other short-term
obligations are valued at amortized cost, which constitutes fair value as
determined by the Board of Trustees. Portfolio securities for which there are no
such quotations or valuations are valued at fair value as determined in good
faith by or at the direction of the Board of Trustees.
 
Generally, trading in foreign securities is substantially completed each day at
various times prior to the close of regular trading on the Exchange.
Occasionally, events affecting the values of such securities may occur between
the times at which they are determined and the close of regular trading on the
Exchange which will not be reflected in the computation of the Fund's net asset
value unless the Trustees deem that such event would materially affect the net
asset value in which case an adjustment would be made.
 
   
All investments and assets are expressed in U.S. dollars based upon current
currency exchange rates. A share's net asset value is effective for orders
received by the dealer prior to its calculation and received by MFD, prior to
the close of that business day.
    
 
PERFORMANCE INFORMATION
 
TOTAL RATE OF RETURN: The Fund will calculate its total rate of return for each
class of shares for certain periods by determining the average annual compounded
rates of return over those periods that would cause an investment of $1,000
(made with all distributions reinvested and reflecting the CDSC or the maximum
public offering price) to reach the value of that investment at the end of the
periods. The Fund may also calculate (i) a total rate of return, which is not
reduced by the CDSC (4% maximum for Class B shares and 1% maximum for Class C
shares) and therefore may result in a higher rate of return, (ii) a total rate
of return assuming an initial account value of $1,000, which will result in a
higher rate of return with respect to Class A shares since the value of the
initial account will not be reduced by the maximum sales charge (currently
5.75%) and/or (iii) total rates of return which represent aggregate performance
over a period or year-by-year performance, and which may or may not reflect the
effect of the maximum or other sales charge or CDSC.
 
                                       22
<PAGE>   187
 
The Fund offers multiple classes of shares which were initially offered for sale
to, and purchased by, the public on different dates (the class "inception
date"). The calculation of total rate of return for a class of shares which has
a later inception date than another class of shares of the Fund is based both on
(i) the performance of the Fund's newer class from it's inception date and (ii)
the performance of the Fund's oldest class from the date it initially was
offered for sale to the public up to the class inception date of the newer
class.
 
As discussed in the Prospectus, the sales charges, expenses and expense ratios,
and therefore the performance, of the Fund's classes of shares differ. In
calculating total rate of return for a newer class of shares in accordance with
certain formulas required by the SEC, the performance will be adjusted to take
into account the fact that the newer class is subject to a different sales
charge than the oldest class (e.g., if the newer class is Class A shares, the
total rate of return quoted will reflect the deduction of the initial sales
charge applicable to Class A shares; if the newer class is Class B shares, the
total rate of return quoted will reflect the deduction of the CDSC applicable to
Class B shares). However, the performance will not be adjusted to take into
account the fact that the newer class of shares bears different class specific
expenses than the oldest class of shares (e.g., Rule 12b-1 fees). Therefore, the
total rate of return quoted for a newer class of shares will differ from the
return that would be quoted had the newer class of shares been outstanding for
the entire period over which the calculation is based (i.e., the total rate of
return quoted for the newer class will be higher than the return that would have
been quoted had the newer class of shares been outstanding for the entire period
over which the calculation is based if the class specific expenses for the newer
class are higher than the class specific expenses of the oldest class, and the
total rate of return quoted for the newer class will be lower than the return
that would be quoted had the newer class of shares been outstanding for this
entire period if the class specific expenses for the newer class are lower than
the class specific expenses of the oldest class).
 
   
Total rate of return quotations for each class are presented in Appendix A
attached hereto.
    
 
   
Any performance results, as well as any yield, tax-equivalent yield or total
rate of return quotation provided by the Fund, should not be considered as
representative of the performance of the Fund in the future since the net asset
value and public offering price of shares of the Fund will vary based not only
on the type, quality and maturities of the securities held in the Fund's
portfolio, but also on changes in the current value of such securities and on
changes in the expenses of the Fund. These factors and possible differences in
the methods used to calculate yields, tax-equivalent yields and total rates of
return should be considered when comparing the yield, tax-equivalent yield and
total rate of return of the Fund to yields, tax-equivalent yields and total
rates of return published for other investment companies or other investment
vehicles. Total rate of return reflects the performance of both principal and
income. Current net asset value as well as account balance information may be
obtained by calling 1-800-MFS-TALK (637-8255).
    
 
From time to time the Fund may, as appropriate, quote Fund rankings or reprint
all or a portion of evaluations of fund performance and operations appearing in
various independent publications, including but not limited to the following:
Money, Fortune, U.S. News and World Report, Kiplinger's Personal Finance, The
Wall Street Journal, Barron's, Investors Business Daily, Newsweek, Financial
World, Financial Planning, Investment Advisor, USA Today, Pensions and
Investments, SmartMoney, Forbes, Global Finance, Registered Representative,
Institutional Investor, the Investment Company Institute, Johnson's Charts,
Morningstar, Lipper Analytical Services, Inc., CDA Wiesenberger, Shearson Lehman
and Salomon Bros. Indices, Ibbotson, Business Week, Lowry Associates, Media
General, Investment Company Data, The New York Times, Your Money, Strangers
Investment Advisor, Financial Planning on Wall Street, Standard and Poor's,
Individual Investor, The 100 Best Mutual Funds You Can Buy, by Gordon K.
Williamson, Consumer Price Index, and Sanford C. Bernstein & Co. Fund
performance may also be compared to the performance of other mutual funds
tracked by financial or business publications or periodicals.
 
The Fund may also quote evaluations mentioned in independent radio or television
broadcasts.
 
From time to time the Fund may use charts and graphs to illustrate the past
performance of various indices such as those mentioned above and illustrations
using hypothetical rates of return to illustrate the effects of compounding and
tax-deferral.
 
   
The Fund may also use charts, graphs or other presentation formats to illustrate
the historical correlation of its performance to fund categories established by
Morningstar (or other nationally recognized statistical ratings organizations)
and to other MFS Funds.
    
 
From time to time, the Fund may discuss or quote its current portfolio manager
as well as other investment personnel, including such persons' views on: the
economy; securities markets; portfolio securities and their issuers; investment
philosophies, strategies, techniques and criteria used in the selection of
securities to be purchased or sold for the Fund; the Fund's portfolio holdings;
the investment research and analysis process; the formulation and evaluation of
investment recommendations; and the assessment and evaluation of credit,
interest rate, market and economic risks, and similar or related matters.
 
From time to time the Fund may also discuss or quote the views of its
distributor, its investment adviser and other financial planning, legal, tax,
accounting, insurance, estate planning and other professionals, or from surveys,
regarding individual and family financial planning. Such views may include
information regarding: retirement planning; tax management strategies; estate
planning; general investment techniques (e.g., asset allocation and disciplined
saving and investing); business succession; ideas and information provided
through the MFS Heritage Planning(sm) program, an intergenerational financial
planning assistance program; issues with respect to insurance (e.g., disability
and life insurance and Medicare supplemental insurance); is-
                                       23
<PAGE>   188
 
sues regarding financial and health care management for elderly family members;
and other similar or related matters.
 
The Fund may advertise examples of the effects of periodic investment plans,
including the principle of dollar cost averaging. In such a program, an investor
invests a fixed dollar amount in a fund at periodic intervals, thereby
purchasing fewer shares when prices are high and more shares when prices are
low. While such a strategy does not assure a profit or guard against a loss in a
declining market, the investor's average cost per share can be lower than if
fixed numbers of shares are purchased at the same intervals.
 
   
From time to time, the Fund may also advertise annual returns showing the
cumulative value of an initial investment in the Fund in various amounts over
specified periods with capital gain and dividend distributions invested in
additional shares or taken in cash, and with no adjustment for any income taxes
(if applicable) payable by shareholders.
    
 
MFS FIRSTS: MFS has a long history of innovations.
 
  -- 1924 -- Massachusetts Investors Trust is established as the first open-end
     mutual fund in America.
 
  -- 1924 -- Massachusetts Investors Trust is the first mutual fund to make full
     public disclosure of its operations in shareholder reports.
 
  -- 1932 -- One of the first internal research departments is established to
     provide in-house analytical capability for an investment management firm.
 
  -- 1933 -- Massachusetts Investors Trust is the first mutual fund to register
     under the Securities Act of 1933 ("Truth in Securities Act" or "Full
     Disclosure Act").
 
  -- 1936 -- Massachusetts Investors Trust is the first mutual fund to allow
     shareholders to take capital gain distributions either in additional shares
     or cash.
 
  -- 1976 -- MFS(R) Municipal Bond Fund is among the first municipal bond funds
     established.
 
  -- 1979 -- Spectrum becomes the first combination fixed/ variable annuity with
     no initial sales charge.
 
   
  -- 1981 -- MFS(R) Global Governments Fund is established as America's first
     globally diversified fixed-income mutual fund.
    
 
  -- 1984 -- MFS(R) Municipal High Income Fund is the first open-end mutual fund
     to seek high tax-free income from lower-rated municipal securities.
 
  -- 1986 -- MFS(R) Managed Sectors Fund becomes the first mutual fund to target
     and shift investments among industry sectors for shareholders.
 
  -- 1986 -- MFS(R) Municipal Income Trust is the first closed-end, high-yield
     municipal bond fund traded on the New York Stock Exchange.
 
  -- 1986 -- MFS(R) Lifetime Investment Program(SM) is established as the first
     complete family of 12b-1 mutual funds with no initial sales charge.
 
  -- 1989 -- MFS(R) Regatta becomes America's first non-qualified
     market-value-adjusted fixed/variable annuity.
 
   
  -- 1990 -- MFS(R) Global Total Return Fund is the first global balanced fund.
    
 
   
  -- 1993 -- MFS(R) Global Growth Fund is the first global emerging markets fund
     to offer the expertise of two sub-advisers.
    
 
   
  -- 1993 -- MFS(R) becomes money manager of MFS(R) Union Standard(R) Equity
     Fund, the first Fund to invest in companies deemed to be union-friendly by
     an Advisory Board of senior labor officials, senior managers of companies
     with significant labor contracts, academics and other national labor
     leaders or experts.
    
 
8. DISTRIBUTION PLAN
 
The Trustees have adopted a Distribution Plan for Class A, Class B and Class C
shares (the "Distribution Plan") pursuant to Section 12(b) of the 1940 Act and
Rule 12b-1 thereunder (the "Rule") after having concluded that there is a
reasonable likelihood that the Distribution Plan would benefit the Fund and each
respective class of shareholders. The provisions of the Distribution Plan are
severable with respect to each class of shares offered by the Fund. The
Distribution Plan is designed to promote sales, thereby increasing the net
assets of the Fund. Such an increase may reduce the Fund's expense ratio to the
extent that the Fund's fixed costs are spread over a larger net asset base.
Also, an increase in net assets may lessen the adverse effect that could result
were the Fund required to liquidate portfolio securities to meet redemptions.
There is, however, no assurance that the net assets of the Fund will increase or
that the other benefits referred to above will be realized.
 
The Distribution Plan is described in the Prospectus under the caption
"Distribution Plan," which is incorporated herein by reference. The following
information supplements this Prospectus discussion.
 
SERVICE FEES. With respect to Class A shares, no service fees will be paid: (i)
to any dealer who is the holder or dealer of record for investors who own Class
A shares having an aggregate net asset value less than $750,000, or such other
amount as may be determined from time to time by MFD (MFD, however, may waive
this minimum amount requirement from time to time); or (ii) to any insurance
company which has entered into an agreement with the Fund and MFD that permits
such insurance company to purchase Class A shares from the Fund at their net
asset value in connection with annuity agreements issued in connection with the
insurance company's separate accounts. Dealers may from time to time be required
to meet certain other criteria in order to receive service fees.
 
With respect to Class B shares, except in the case of the first year service
fee, no service fees will be paid to any securities dealer who is the holder or
dealer of record for investors who own Class B shares having an aggregate net
asset value of less than $750,000 or such other amount as may be determined by
 
                                       24
<PAGE>   189
 
MFD from time to time. MFD, however, may waive this minimum amount requirement
from time to time. Dealers may from time to time be required to meet certain
other criteria in order to receive service fees.
 
MFD or its affiliates shall be entitled to receive any service fee payable under
the Distribution Plan for which there is no dealer of record or for which
qualification standards have not been met as partial consideration for personal
services and/or account maintenance services performed by MFD or its affiliates
for shareholder accounts.
 
DISTRIBUTION FEES: The purpose of distribution payments to MFD under the
Distribution Plan is to compensate MFD for its distribution services to the
Fund. MFD pays commissions to dealers as well as expenses of printing
prospectuses and reports used for sales purposes, expenses with respect to the
preparation and printing of sales literature and other distribution related
expenses, including, without limitation, the cost necessary to provide
distribution-related services, or personnel, travel, office expenses and
equipment.
 
   
DISTRIBUTION AND SERVICE FEES PAID DURING THE FUND'S LAST FISCAL YEAR: During
the fiscal year ended August 31, 1998, the Fund paid the following Distribution
Plan expenses:
    
 
   
<TABLE>
<CAPTION>
                             AMOUNT OF       AMOUNT OF       AMOUNT OF
                            DISTRIBUTION   DISTRIBUTION    DISTRIBUTION
                            AND SERVICE     AND SERVICE     AND SERVICE
                            FEES PAID BY   FEES RETAINED   FEES RECEIVED
    CLASSES OF SHARES           FUND          BY MFD        BY DEALERS
    -----------------       ------------   -------------   -------------
<S>                         <C>            <C>             <C>
Class A Shares                $115,711        $13,896        $101,815
Class B Shares                 760,129        579,952         180,177
Class C Shares                  64,890            225          64,665
</TABLE>
    
 
   
GENERAL: The Distribution Plan will remain in effect until August 1, 1999, and
will continue in effect thereafter only if such continuance is specifically
approved at least annually by vote of both the Trustees and a majority of the
Trustees who are not "interested persons" or financially interested parties of
such Plan ("Distribution Plan Qualified Trustees"). The Distribution Plan also
requires that the Fund and MFD each shall provide the Trustees, and the Trustees
shall review, at least quarterly, a written report of the amounts expended (and
purposes therefor) under such Plan. The Distribution Plan may be terminated at
any time by vote of a majority of the Distribution Plan Qualified Trustees or by
vote of the holders of a majority of the respective class of the Fund's shares
(as defined in "Investment Restrictions"). All agreements relating to the
Distribution Plan entered into between the Fund or MFD and other organizations
must be approved by the Board of Trustees, including a majority of the
Distribution Plan Qualified Trustees. Agreements under the Distribution Plan
must be in writing, will be terminated automatically if assigned, and may be
terminated at any time without payment of any penalty, by vote of a majority of
the Distribution Plan Qualified Trustees or by vote of the holders of a majority
of the respective class of the Fund's shares. The Distribution Plan may not be
amended to increase materially the amount of permitted distribution expenses
without the approval of a majority of the respective class of the Fund's shares
(as defined in "Investment Restrictions") or may not be materially amended in
any case without a vote of the Trustees and a majority of the Distribution Plan
Qualified Trustees. The selection and nomination of Distribution Plan Qualified
Trustees shall be committed to the discretion of the non-interested Trustees
then in office. No Trustee who is not an "interested person" has any financial
interest in the Distribution Plan or in any related agreement.
    
 
9. DESCRIPTION OF SHARES, VOTING RIGHTS AND LIABILITIES
 
The Declaration of Trust permits the Trustees to issue an unlimited number of
full and fractional Shares of Beneficial Interest (without par value) of one or
more separate series and to divide or combine the shares of any series into a
greater or lesser number of shares without thereby changing the proportionate
beneficial interests in that series. The Trustees have currently authorized
shares of the Fund and three other series. The Declaration of Trust further
authorizes the Trustees to classify or reclassify any series of shares into one
or more classes. Pursuant thereto, the Trustees have authorized the issuance of
one class of shares for each of the Trust's two money market series, and Class A
and Class B shares of one other of the Trust's four series. In addition, the
Trustees have authorized the issuance of Class A shares, Class B shares, Class C
shares and Class I shares for the Fund. Each share of a class of the Fund
represents an equal proportionate interest in the assets of the Fund allocable
to that class. Upon liquidation of the Fund, shareholders of each class of the
Fund are entitled to share pro rata in the Fund's net assets allocable to such
class available for distribution to shareholders. The Trust reserves the right
to create and issue additional series or classes of shares, in which case the
shares of each class of a series would participate equally in the earnings,
dividends and assets allocable to that class of the particular series.
 
Shareholders are entitled to one vote for each share held and may vote in the
election of Trustees and on other matters submitted to meetings of shareholders.
Although Trustees are not elected annually by the shareholders, shareholders
have, under certain circumstances, the right to remove one or more Trustees in
accordance with the provisions of section 16(c) of the 1940 Act. No material
amendment may be made to the Declaration of Trust without the affirmative vote
of a majority of the Trust shares (as defined in "Investment Restrictions") or
by an instrument in writing without a meeting, signed by a majority of Trustees
and consented to by the holders of not less than a majority of the shares
outstanding and entitled to vote. Shares have no pre-emptive or conversion
rights (except as described in the Prospectus under "Purchases -- Conversion of
Class B Shares"). Shares are fully paid and non-assessable. The Trust may enter
into a merger or consolidation, or sell all or substantially all of its assets
(or all or substantially all of the assets belonging to any series of the
Trust), if approved by the vote of the holders of two-thirds of the Trust's
outstanding shares voting as a single class, or of the affected series of the
Trust, as the case may be, except that if the Trustees of the
 
                                       25
<PAGE>   190
 
Trust recommend such merger, consolidation or sale, the approval by vote of the
holders of a majority of the Trust's or the affected series' outstanding shares
(as defined in "Investment Restrictions") will be sufficient. The Trust or any
series of the Trust may also be terminated (i) upon liquidation and distribution
of its assets, if approved by the vote of the holders of two-thirds of its
outstanding shares, or (ii) by the Trustees by written notice to the
shareholders of the Trust or the affected series. If not so terminated the Trust
will continue indefinitely.
 
The Trust is an entity of the type commonly known as a "Massachusetts business
trust." Under Massachusetts law, shareholders of such a trust may, under certain
circumstances, be held personally liable as partners for its obligations.
However, the Declaration of Trust contains an express disclaimer of shareholder
liability for acts, obligations or affairs of the Trust and provides for
indemnification and reimbursement of expenses out of the Trust property for any
shareholder held personally liable for the obligations of the Trust. The
Declaration of Trust also provides that the Trust shall maintain appropriate
insurance (for example, fidelity bonding and errors and omissions insurance) for
the protection of the Trust, its shareholders, Trustees, officers, employees and
agents covering possible tort and other liabilities. Thus, the risk of a
shareholder incurring financial loss on account of shareholder liability is
limited to circumstances in which both inadequate insurance existed and the
Trust itself was unable to meet its obligations.
 
The Declaration of Trust further provides that obligations of the Trust are not
binding upon the Trustees individually but only upon the property of the Trust
and that the Trustees will not be liable for any action or failure to act, but
nothing in the Declaration of Trust protects a Trustee against any liability to
which he would otherwise be subject by reason of willful misfeasance, bad faith,
gross negligence or reckless disregard of the duties involved in the conduct of
his office.
 
10. INDEPENDENT AUDITORS AND FINANCIAL STATEMENTS
 
Deloitte & Touche LLP are the Fund's independent auditors providing audit
services, tax return preparation and assistance and consultation with respect to
the preparation of filings with the SEC.
 
   
The Portfolio of Investments at August 31, 1998, the Statement of Assets and
Liabilities at August 31, 1998, the Statement of Operations for the year ended
August 31, 1998, the Statements of Changes in Net Assets for the years ended
August 31, 1998 and 1997, and the Notes to Financial Statements and the
Independent Auditors' Report, each of which is included in the Annual Report to
Shareholders of the Fund, are incorporated by reference into this SAI and have
been so incorporated in reliance upon the report of Deloitte & Touche LLP,
independent auditors, as experts in accounting and auditing. A copy of the
Annual Report accompanies this SAI.
    
 
                                       26
<PAGE>   191
 
                                                                      APPENDIX A
 
                            PERFORMANCE INFORMATION
 
   
The performance quotations below should not be considered as representative of
the performance of the Fund in the future since the net asset value and public
offering price of shares of the Fund will vary. See "Performance Information" in
the SAI.
    
 
   
All performance quotations are as of August 31, 1998.
    
 
   
<TABLE>
<CAPTION>
                                                                          LIFE OF
                                                              1 YEAR       FUND
                                                              ------      -------
<S>                                                           <C>         <C>
Class A with sales charge...................................  -20.30%      7.45%(1)
Class A without sales charge................................  -15.44%      8.80%(1)
Class B with CDSC...........................................  -19.33%      7.54%(1)
Class B without CDSC........................................  -16.05%      7.85%(1)
Class C with CDSC...........................................  -16.82%      7.75%(2)
Class C without CDSC........................................  -16.00%      7.75%(2)
Class I shares..............................................  -15.23%      8.56%(3)
</TABLE>
    
 
- ---------------
 
(1) From the inception of Class A and B shares on December 1, 1993.
 
(2) Class C share performance includes the performance of the Fund's Class A
    shares for periods prior to the inception of Class C shares on August 1,
    1994. Sales charges, expenses and expense ratios, and therefore performance,
    for Class A and Class C shares differ. Class C share performance has been
    adjusted to reflect that Class C shares generally are subject to CDSC
    (unless the performance quotation does not give effect to the CDSC), whereas
    Class A shares generally are subject to an initial sales charge. Class C
    share performance has not, however, been adjusted to reflect differences in
    operating expenses (e.g., Rule 12b-1 fees), which generally are lower for
    Class A shares.
 
(3) Class I share performance includes the performance of the Fund's Class A
    shares for the periods prior to the inception of Class I shares on January
    2, 1997. Sales charges, expenses and expense ratios, and therefore
    performance, for Class I and Class A shares differ. Class I share
    performance has been adjusted to reflect that Class I shares are not subject
    to an initial sales charge, whereas Class A shares generally are subject to
    an initial sales charge. Class I share performance has not, however, been
    adjusted to reflect differences in operating expenses (e.g., Rule 12b-1
    fees), which generally are lower for Class I shares.
 
                                       A-1
<PAGE>   192
 
INVESTMENT ADVISER
Massachusetts Financial Services Company
500 Boylston Street, Boston, MA 02116
(617) 954-5000
 
DISTRIBUTOR
MFS Fund Distributors, Inc.
500 Boylston Street, Boston, MA 02116
(617) 954-5000
 
CUSTODIAN
State Street Bank and Trust Company
225 Franklin Street, Boston, MA 02110
 
DIVIDEND DISBURSING AGENT
State Street Bank and Trust Company
225 Franklin Street, Boston, MA 02110
 
SHAREHOLDER SERVICING AGENT
MFS Service Center, Inc.
500 Boylston Street, Boston, MA 02116
Toll free: (800) 225-2606
 
Mailing Address:
P.O. Box 2281, Boston, MA 02107-9906
 
INDEPENDENT AUDITORS
Deloitte & Touche LLP
125 Summer Street, Boston, MA 02110
 
MFS(R) MID CAP GROWTH FUND
 
500 BOYLSTON STREET
BOSTON, MA 02116
 
[MFS INVESTMENT MANAGEMENT LOGO]                     MMC-13-9/97/525  83/283/383
<PAGE>   193
                                     PART C


ITEM 24.   FINANCIAL STATEMENTS AND EXHIBITS

           FOR MFS MONEY MARKET FUND AND MFS GOVERNMENT MONEY MARKET FUND

   
           (a)    FINANCIAL STATEMENTS INCLUDED IN PART A:
                        For the six years ended October 31, 1993, the ten
                        months ended August 31, 1994, and the four years
                        ended August 31, 1998:
                             Financial Highlights
    

   
                  FINANCIAL STATEMENTS INCLUDED IN PART B:
                        At August 31, 1998:
                             Statement of Assets and Liabilities*
                             Portfolio of Investments*
    

   
             For the two years in the period ended August 31, 1998:
                       Statement of Changes in Net Assets*
    

- ----------------------

   
*    Incorporated herein by reference to the Fund's Annual Report to
     Shareholders dated August 31, 1998, filed with the SEC via EDGAR on October
     28, 1998.
    

                  FOR MFS MUNICIPAL BOND FUND

   
                  (a)    FINANCIAL STATEMENTS INCLUDED IN PART A:
                               For the six years ended October 31, 1993, the ten
                               months ended August 31, 1994, and the four years
                               ended August 31, 1998:
                                    Financial Highlights
    

   
                         FINANCIAL STATEMENTS INCLUDED IN PART B:
                               At August 31, 1998:
                                    Statement of Assets and Liabilities*
                                    Portfolio of Investments*
    

   
             For the two years in the period ended August 31, 1998:
                       Statement of Changes in Net Assets*
    
- ----------------------

   
*    Incorporated herein by reference to the Fund's Annual Report to
     Shareholders dated August 31, 1998, filed with the SEC via EDGAR on October
     28, 1998.
    
<PAGE>   194
                  FOR MFS MID CAP GROWTH  FUND

   
                  (a)    FINANCIAL STATEMENTS INCLUDED IN PART A:
                               For the period from December 1, 1993 to August
                               31, 1994 and for the four years ended August 31,
                               1998:
                                    Financial Highlights
    

   
                         FINANCIAL STATEMENTS INCLUDED IN PART B:
                               At August 31, 1998:
                                    Statement of Assets and Liabilities*
                                    Portfolio of Investments*
    

   
                         For the two years in the period ended August 31, 1998:
                         Statement of Changes in Net Assets*
    

   
                         For the year ended August 31, 1998:
                         Statement of Operations*
    
- --------------------

   
*    Incorporated herein by reference to the Fund's Annual Report to
     Shareholders dated August 31, 1998, filed with the SEC via EDGAR on October
     28, 1998.
    

                  (b)    EXHIBITS

                          1    (a)    Amended and Restated Declaration of Trust,
                                      dated January 19, 1995.  (1)

                               (b)    Amendment to Declaration of Trust, dated
                                      June 20, 1996.  (7)

   
                               (c)    Amendment to Declaration of Trust, dated
                                      August 29, 1997; filed herewith.
    

                          2           Amended and Restated By-Laws, dated
                                      December 21, 1994.  (1)

                          3           Not Applicable.

                          4           Form of Share Certificate for Classes
                                      of Shares.  (6)

                          5    (a)    Investment Advisory Agreement by and
                                      between Massachusetts Cash Management
                                      Trust, on behalf of MFS Money Market Fund
                                      and MFS Government Money Market Fund,
                                      dated May 20, 1982 and amended and
                                      restated August 1, 1993. (1)
<PAGE>   195
                               (b)    Investment Advisory Agreement by and
                                      between MFS Series Trust IV, on behalf
                                      of MFS Municipal Bond Fund, dated
                                      September 1, 1993.  (1)

                               (c)    Investment Advisory Agreement by and
                                      between MFS Series Trust IV, on behalf of
                                      MFS OTC Fund, dated October 20, 1993. (1)

                          6    (a)    Distribution Agreement between the
                                      Trust and MFS Fund Distributors, Inc.,
                                      dated January 1, 1995. (1)

                               (b)    Dealer Agreement between MFS Fund
                                      Distributors, Inc. ("MFD"), and a dealer,
                                      and the Mutual Fund Agreement between MFD
                                      and a bank or NASD affiliate, as amended
                                      April 11, 1997. (5)

                          7           Retirement Plan for Non-Interested Person
                                      Trustees, dated January 1, 1991. (1)

                          8    (a)    Custodian Agreement between Registrant and
                                      State Street Bank and Trust Company, dated
                                      April 25, 1988. (4)

                               (b)    Amendment to Custodian Contract, dated
                                      April 25, 1988. (4)

                               (c)    Amendment to Custodian Contract, dated
                                      October 1, 1989. (4)

                               (d)    Amendment to Custodian Contract, dated
                                      September 17, 1991. (4)

                          9    (a)    Shareholder Servicing Agent Agreement,
                                      dated August 1, 1985. (1)

   
                               (b)    Amendment to Shareholder Servicing
                                      Agreement dated January 1, 1998 to amend
                                      Fee Schedule; filed herewith.
    

                               (c)    Exchange Privilege Agreement, dated July
                                      30, 1997. (11).

                               (d)    Loan Agreement among MFS Borrowers and The
                                      First National Bank of Boston, dated as of
                                      February 21, 1995. (9)

   
                               (e)    Third Amendment to the Loan Agreement
                                      among MFS Borrowers and The First National
                                      Bank of Boston, dated as of February 14,
                                      1997. (9)
    
<PAGE>   196
                               (f)    Dividend Disbursing Agent Agreement, dated
                                      February 1, 1986. (2)

   
                               (g)    Master Administrative Services Agreement,
                                      dated March 1, 1997, as amended. (12)
    

   
                         10           Consent and Opinion of Counsel, dated
                                      December 22, 1997. (10)
    

                         11           Consent of Deloitte & Touche LLP; filed
                                      herewith.

                         12           Not Applicable.

                         13           Not Applicable.

                         14    (a)    Forms for Individual Retirement
                                      Account Disclosure Statement, as currently
                                      in effect. (3)

                               (b)    Forms 403(b) Custodial Account Agreement,
                                      as currently in effect. (3)



                               (c)    Forms for MFS Prototype Paired Defined
                                      Contribution Plans as Trust Agreement, as
                                      currently in effect. (3)

   
                               (d)    Forms for Roth Individual Retirement
                                      Account Disclosure Statement and Trust
                                      Agreement as currently in effect. (8)
    


                         15    (a)    Master Distribution Plan Pursuant to
                                      Rule 12b-1 Under the Investment Company
                                      Act of 1940, effective January 1, 1997.
                                      (10)

   
                               (b)    Exhibits as revised October 21, 1998 to
                                      Master Distribution Plan pursuant to Rule
                                      12b-1 under the Investment Company Act of
                                      1940 to replace those exhibits to the
                                      Master Distribution Plan contained in
                                      Exhibit 15(a) above. (13)
    

                         16    (a)    Schedule for Computation of
                                      Performance Quotations for MFS Money
                                      Market Fund and MFS Government Money
                                      Market Fund - Seven-Day Yield Calculation.
                                      (1)

                               (b)    Schedule for Computation of Performance
                                      Quotations for MFS Municipal Bond Fund -
                                      Yield, Tax-Equivalent Yield, Distribution
                                      Rate and Average Annual Total Return. (1)
<PAGE>   197
                               (c)    Schedule for Computation of Performance
                                      Quotations for MFS Mid Cap Growth Fund
                                      (formerly MFS OTC Fund) - Average Annual
                                      Total Return. (1)

                         17           Financial Data Schedules for each class of
                                      each series; filed herewith.


   
                         18           Plan pursuant to Rule 18f-3(d) under the
                                      Investment Company Act of 1940, as amended
                                      and restated May 27, 1998. (14)
    

   
                                      Power of Attorney, dated September 21,
                                      1994. (1) Power of Attorney, dated
                                      February 19, 1998; filed herewith.
    


- -----------------------------

(1)      Incorporated by reference to the Registrant's Post-Effective Amendment
         No. 26 filed with the SEC via EDGAR on February 28, 1995.

(2)      Incorporated by reference to MFS Municipal Series Trust (File Nos.
         2-92915 and 811-4096) Post-Effective Amendment No. 28 filed with the
         SEC via EDGAR on July 28, 1995.

(3)      Incorporated by reference to MFS Series Trust IX (File Nos. 2-50409 and
         811-2464) Post-Effective Amendment No. 32 filed with the SEC via EDGAR
         on August 28, 1995.

(4)      Incorporated by reference to the Registrant's Post-Effective Amendment
         No. 27 filed with the SEC via EDGAR on October 11, 1995.

(5)      Incorporated by reference to MFS Series Trust III (File Nos. 2-60491
         and 811-2794) Post-Effective Amendment No. 24 filed with the SEC via
         EDGAR on May 29, 1997.

(6)      Incorporated by reference to MFS Series Trust I (File Nos. 33-7638 and
         811-4777) Post-Effective Amendment No. 25 filed with the SEC via EDGAR
         on August 28, 1996.

(7)      Incorporated by reference to Registrant's Post-Effective Amendment No.
         29 filed with the SEC on August 28, 1996.

   
(8)      Incorporated by reference to MFS Series Trust VIII (File Nos. 33-37972
         and 811-5262) Post-Effective Amendment No. 14 filed with the SEC via
         EDGAR on February 26, 1998.
    

(9)      Incorporated by reference to MFS Series Trust I (File Nos. 33-7638 and
         811-4777) Post-Effective Amendment No. 28 filed with the SEC via EDGAR
         on June 26, 1997.

   
(10)     Incorporated by reference to the Registrant's Post-Effective Amendment
         No. 32 filed with the SEC via EDGAR on December 23, 1997.
    

(11)     Incorporated by reference to Massachusetts Investors Growth Stock Fund
         (File Nos. 2-14677 and 811-859) Post-Effective Amendment No. 64 filed
         with the SEC via EDGAR on October 29, 1997.

   
(12)     Incorporated by reference to Massachusetts Investors Growth Stock Fund
         (File Nos. 2-14677 and 811-859) Post-Effective Amendment No. 65 filed
         with the SEC via EDGAR on March 30, 1998.
    

   
(13)     Incorporated by reference to MFS Series Trust IX (File Nos. 2-50409 and
         811-2464) Post-Effective Amendment No. 36 filed with the SEC via EDGAR
         on October 15, 1998.
    

   
(14)     Incorporated by reference to MFS Series Trust II (File Nos. 33-7637 and
         811-4775) Post-Effective Amendment No. 27 filed with the SEC via EDGAR
         on May 29, 1998.
    

 ITEM 25.         PERSONS CONTROLLED BY OR UNDER COMMON CONTROL WITH REGISTRANT

                  Not applicable.
<PAGE>   198
   
 ITEM 26.         INDEMNIFICATION
    

                  The Trustees and officers of the Trust and the personnel of
the Trust's investment adviser and principal underwriter are insured under an
errors and omissions liability insurance policy. The Trust and its officers are
also insured under the fidelity bond required by Rule 17g-1 under the Investment
Company Act of 1940, as amended.

                  Reference is hereby made to (a) Article V of the Trust's
Declaration of Trust, and (b) Section 9 of the Shareholder Servicing Agent
Agreement both incorporated by reference to Post-Effective Amendment No. 26,
filed with the SEC via EDGAR on February 28, 1995.

   
ITEM 27. BUSINESS AND OTHER CONNECTIONS OF INVESTMENT ADVISER
    

   
                  MFS serves as investment adviser to the following open-end
Funds comprising the MFS Family of Funds (except the Vertex Funds mentioned
below): Massachusetts Investors Trust, Massachusetts Investors Growth Stock
Fund, MFS Growth Opportunities Fund, MFS Government Securities Fund, MFS
Government Limited Maturity Fund, MFS Series Trust I (which has thirteen series:
MFS Managed Sectors Fund, MFS Cash Reserve Fund, MFS Global Asset Allocation
Fund, MFS Strategic Growth Fund, MFS Research Growth and Income Fund, MFS Core
Growth Fund, MFS Equity Income Fund, MFS Special Opportunities Fund, MFS
Convertible Securities Fund, MFS Blue Chip Fund, MFS New Discovery Fund, MFS
Science and Technology Fund and MFS Research International Fund), MFS Series
Trust II (which has four series: MFS Emerging Growth Fund, MFS Large Cap Growth
Fund, MFS Intermediate Income Fund and MFS Charter Income Fund), MFS Series
Trust III (which has three series: MFS High Income Fund, MFS Municipal High
Income Fund and MFS High Yield Opportunities Fund), MFS Series Trust IV (which
has four series: MFS Money Market Fund, MFS Government Money Market Fund, MFS
Municipal Bond Fund and MFS Mid Cap Growth Fund), MFS Series Trust V (which has
five series: MFS Total Return Fund, MFS Research Fund, MFS International
Opportunities Fund, MFS International Strategic Growth Fund and MFS
International Value Fund), MFS Series Trust VI (which has three series: MFS
Global Total Return Fund, MFS Utilities Fund and MFS Global Equity Fund), MFS
Series Trust VII (which has two series: MFS Global Governments Fund and MFS
Capital Opportunities Fund), MFS Series Trust VIII (which has two series: MFS
Strategic Income Fund and MFS Global Growth Fund), MFS Series Trust IX (which
has five series: MFS Bond Fund, MFS Limited Maturity Fund, MFS Municipal Limited
Maturity Fund, MFS Research Bond Fund and MFS Intermediate Investment Grade Bond
Fund), MFS Series Trust X (which has seven series: MFS Government Mortgage Fund,
MFS/Foreign & Colonial Emerging Markets Equity Fund, MFS International Growth
Fund, MFS International Growth and Income Fund, MFS Strategic Value Fund, MFS
Small Cap Value Fund and MFS Emerging Markets Debt Fund), MFS Series Trust XI
(which has four series: MFS Union Standard Equity Fund, Vertex All Cap Fund,
Vertex U.S. All Cap Fund and Vertex Contrarian Fund), and MFS Municipal Series
Trust (which has 16 series: MFS Alabama Municipal Bond Fund, MFS Arkansas
Municipal Bond Fund, MFS California Municipal Bond Fund, MFS Florida Municipal
Bond Fund, MFS Georgia Municipal Bond Fund, MFS
    
<PAGE>   199
   
Maryland Municipal Bond Fund, MFS Massachusetts Municipal Bond Fund, MFS
Mississippi Municipal Bond Fund, MFS New York Municipal Bond Fund, MFS North
Carolina Municipal Bond Fund, MFS Pennsylvania Municipal Bond Fund, MFS South
Carolina Municipal Bond Fund, MFS Tennessee Municipal Bond Fund, MFS Virginia
Municipal Bond Fund, MFS West Virginia Municipal Bond Fund and MFS Municipal
Income Fund) (the "MFS Funds"). The principal business address of each of the
MFS Funds is 500 Boylston Street, Boston, Massachusetts 02116.
    

   
                  MFS also serves as investment adviser of the following
open-end Funds: MFS Institutional Trust ("MFSIT") (which has ten series) and MFS
Variable Insurance Trust ("MVI") (which has thirteen series). The principal
business address of each of the aforementioned funds is 500 Boylston Street,
Boston, Massachusetts 02116.
    

   
                  In addition, MFS serves as investment adviser to the following
closed-end funds: MFS Municipal Income Trust, MFS Multimarket Income Trust, MFS
Government Markets Income Trust, MFS Intermediate Income Trust, MFS Charter
Income Trust and MFS Special Value Trust (the "MFS Closed-End Funds"). The
principal business address of each of the MFS Closed-End Funds is 500 Boylston
Street, Boston, Massachusetts 02116.
    

   
                  Lastly, MFS serves as investment adviser to MFS/Sun Life
Series Trust ("MFS/SL") (which has 26 series), Money Market Variable Account,
High Yield Variable Account, Capital Appreciation Variable Account, Government
Securities Variable Account, World Governments Variable Account, Total Return
Variable Account and Managed Sectors Variable Account (collectively, the
"Accounts"). The principal business address of MFS/SL is 500 Boylston Street,
Boston, Massachusetts 02116. The principal business address of each of the
aforementioned Accounts is One Sun Life Executive Park, Wellesley Hills,
Massachusetts 02181.
    

   
                  Vertex Investment Management, Inc., a Delaware corporation and
a wholly owned subsidiary of MFS, whose principal business address is 500
Boylston Street, Boston, Massachusetts 02116 ("Vertex"), serves as investment
adviser to Vertex All Cap Fund, Vertex U.S. All Cap Fund and Vertex Contrarian
Fund, each a series of MFS Series Trust XI. The principal business address of
the aforementioned Funds is 500 Boylston Street, Boston, Massachusetts 02116.
    

   
                  MFS International Ltd. ("MIL"), a limited liability company
organized under the laws of Bermuda and a subsidiary of MFS, whose principal
business address is Cedar House, 41 Cedar Avenue, Hamilton HM12 Bermuda, serves
as investment adviser to and distributor for MFS American Funds known as the MFS
Funds after January 1999 (which will have 11 portfolios as of January 1999):
U.S. Equity Fund, U.S. Emerging Growth Fund, U.S. High Yield Bond Fund, U.S.
Dollar Reserve Fund, Charter Income Fund, U.S. Research Fund, U.S. Strategic
Growth Fund, Global Equity Fund, European Equity Fund and European Corporate
Bond Fund) (the "MIL Funds"). The MIL Funds are organized in Luxembourg and
qualify as an undertaking for collective investments in transferable securities
(UCITS). The principal business address of the MIL Funds is 47, Boulevard Royal,
L-2449 Luxembourg.
    
<PAGE>   200
   
                  MIL also serves as investment adviser to and distributor for
MFS Meridian U.S. Government Bond Fund, MFS Meridian Charter Income Fund, MFS
Meridian Global Governments Fund, MFS Meridian U.S. Emerging Growth Fund, MFS
Meridian Global Equity Fund, MFS Meridian Limited Maturity Fund, MFS Meridian
Global Growth Fund, MFS Meridian Money Market Fund, MFS Meridian Global Balanced
Fund, MFS Meridian U.S. Equity Fund, MFS Meridian Research Fund, MFS Meridian
U.S. High Yield Fund, MFS Meridian Emerging Markets Debt Fund, MFS Meridian
Strategic Growth Fund and MFS Meridian Global Asset Allocation Fund and the MFS
Meridian Research International Fund (collectively the "MFS Meridian Funds").
Each of the MFS Meridian Funds is organized as an exempt company under the laws
of the Cayman Islands. The principal business address of each of the MFS
Meridian Funds is P.O. Box 309, Grand Cayman, Cayman Islands, British West
Indies.
    

   
                  MFS International (U.K.) Ltd. ("MIL-UK"), a private limited
company registered with the Registrar of Companies for England and Wales whose
current address is 4 John Carpenter Street, London, England ED4Y 0NH, is
involved primarily in marketing and investment research activities with respect
to private clients and the MIL Funds and the MFS Meridian Funds.

    

   
                  MFS Institutional Advisors (Australia) Ltd.
("MFSI-Australia"), a private limited company organized under the Corporations
Law of New South Wales, Australia whose current address is Level 37, Governor
Phillip Tower, One Farrer Place, Sydney, N5W2000, Australia, is involved
primarily in investment management and distribution of Australian superannuation
unit trusts and acts as an investment adviser to institutional accounts.

    

   
                  MFS Holdings Australia Pty Ltd. ("MFS Holdings Australia"), a
private limited company organized pursuant to the Corporations Law of New South
Wales, Australia whose current address is Level 37, Governor Phillip Tower, One
Farrer Place, Sydney, NSW2000 Australia, and whose function is to serve
primarily as a holding company.
    

   
                  MFS Fund Distributors, Inc. ("MFD"), a wholly owned subsidiary
of MFS, serves as distributor for the MFS Funds, MVI and MFSIT.
    

   
                  MFS Service Center, Inc. ("MFSC"), a wholly owned subsidiary
of MFS, serves as shareholder servicing agent to the MFS Funds, the MFS
Closed-End Funds, MFSIT and MVI.
    

   
                  MFS Institutional Advisors, Inc. ("MFSI"), a wholly owned
subsidiary of MFS, provides investment advice to substantial private clients.
    

   
                  MFS Retirement Services, Inc. ("RSI"), a wholly owned
subsidiary of MFS, markets MFS products to retirement plans and provides
administrative and record keeping services for retirement plans.
    
<PAGE>   201
   
                  Massachusetts Investment Management Co., Ltd. (MIMCO), a
wholly owned subsidiary of MFS, is a corporation incorporated in Japan. MIMCO,
whose address is Kamiyacho-Mori Building, 3-20, Tranomon 4-chome, Minato-ku,
Tokyo, Japan, is involved in investment management activities.
    

   
                  MIMCO
    

   
                  Jeffrey L. Shames, Arnold D. Scott and Mamoru Ogata are
Directors, Shaun Moran is the Representative Director, Joseph W. Dello Russo is
the Statutory Auditor, Robert DiBella is the President and Thomas B. Hastings is
the Assistant Statutory Auditor.
    

   
                  MFS
    

   
                  The Directors of MFS are Jeffrey L. Shames, Arnold D. Scott,
John W. Ballen, Kevin R. Parke, Thomas J. Cashman, Jr., Joseph W. Dello Russo,
William W. Scott, Donald A. Stewart and John D. McNeil. Mr. Shames is the
Chairman and Chief Executive Officer, Mr. Ballen is President and Chief
Investment Officer, Mr. Arnold Scott is a Senior Executive Vice President and
Secretary, Mr. William Scott, Mr. Cashman, Mr. Dello Russo and Mr. Parke are
Executive Vice Presidents (Mr. Parke is also Chief Equity Officer), Stephen E.
Cavan is a Senior Vice President, General Counsel and an Assistant Secretary,
Robert T. Burns is a Senior Vice President, Associate General Counsel and an
Assistant Secretary of MFS, and Thomas B. Hastings is a Vice President and
Treasurer of MFS.
    

   
                  MASSACHUSETTS INVESTORS TRUST
                  MASSACHUSETTS INVESTORS GROWTH STOCK FUND
                  MFS GROWTH OPPORTUNITIES FUND
                  MFS GOVERNMENT SECURITIES FUND
                  MFS SERIES TRUST I
                  MFS SERIES TRUST V
                  MFS SERIES TRUST VI
                  MFS SERIES TRUST X
                  MFS GOVERNMENT LIMITED MATURITY FUND
    

   
                  Stephen E. Cavan is the Secretary, W. Thomas London is the
Treasurer, James O. Yost, Ellen M. Moynihan and Mark E. Bradley, Vice Presidents
of MFS, are the Assistant Treasurers, James R. Bordewick, Jr., Senior Vice
President and Associate General Counsel of MFS, is the Assistant Secretary.
    

   
                  MFS SERIES TRUST II
    

   
                  Leslie J. Nanberg, Senior Vice President of MFS, is a Vice
President, Stephen E. Cavan is the Secretary, W. Thomas London is the Treasurer,
James O. Yost, Ellen M. Moynihan and Mark E. Bradley are the Assistant
Treasurers, and James R. Bordewick, Jr. is the Assistant Secretary.
    
<PAGE>   202
   
                  MFS GOVERNMENT MARKETS INCOME TRUST
                  MFS INTERMEDIATE INCOME TRUST
    

   
                  Leslie J. Nanberg, Senior Vice President of MFS, is a Vice
President, Stephen E. Cavan is the Secretary, W. Thomas London is the Treasurer,
James O. Yost, Ellen M. Moynihan and Mark E. Bradley are the Assistant
Treasurers, and James R. Bordewick, Jr. is the Assistant Secretary.
    

   
                  MFS SERIES TRUST III
    

   
                  James T. Swanson, Robert J. Manning and Joan S. Batchelder,
Senior Vice Presidents of MFS, and Bernard Scozzafava, Vice President of MFS,
are Vice Presidents, Stephen E. Cavan is the Secretary, W. Thomas London is the
Treasurer, James O. Yost, Ellen M. Moynihan and Mark E. Bradley are the
Assistant Treasurers, and James R. Bordewick, Jr. is the Assistant Secretary.
    

   
                  MFS SERIES TRUST IV
                  MFS SERIES TRUST IX
    

   
                  Robert A. Dennis and Geoffrey L. Kurinsky, Senior Vice
Presidents of MFS, are Vice Presidents, Stephen E. Cavan is the Secretary, W.
Thomas London is the Treasurer, James O. Yost, Ellen M. Moynihan and Mark E.
Bradley are the Assistant Treasurers and James R. Bordewick, Jr. is the
Assistant Secretary.
    

   
                  MFS SERIES TRUST VII
    

   
                  Leslie J. Nanberg and Stephen C. Bryant, Senior Vice
Presidents of MFS, are Vice Presidents, Stephen E. Cavan is the Secretary, W.
Thomas London is the Treasurer, James O. Yost, Ellen M. Moynihan and Mark E.
Bradley are the Assistant Treasurers and James R. Bordewick, Jr. is the
Assistant Secretary.
    

   
                  MFS SERIES TRUST VIII
    

   
                  Jeffrey L. Shames, Leslie J. Nanberg and James T. Swanson and
John D. Laupheimer, Jr., a Senior Vice President of MFS, are Vice Presidents,
Stephen E. Cavan is the Secretary, W. Thomas London is the Treasurer, James O.
Yost, Ellen M. Moynihan and Mark E. Bradley are the Assistant Treasurers and
James R. Bordewick, Jr. is the Assistant Secretary.
    

   
                  MFS MUNICIPAL SERIES TRUST
    

   
                  Robert A. Dennis is Vice President, Geoffrey L. Schechter,
Vice President of MFS, is Vice President, Stephen E. Cavan is the Secretary, W.
Thomas London is the Treasurer, James O. Yost, Ellen M. Moynihan and Mark E.
Bradley are the Assistant Treasurers and James R. Bordewick, Jr. is the
Assistant Secretary.
    
<PAGE>   203
   
                  MFS VARIABLE INSURANCE TRUST
                  MFS SERIES TRUST XI
                  MFS INSTITUTIONAL TRUST
    

   
                  Jeffrey L. Shames is the President and Chairman, Stephen E.
Cavan is the Secretary, W. Thomas London is the Treasurer, James O. Yost, Ellen
M. Moynihan and Mark E. Bradley are the Assistant Treasurers and James R.
Bordewick, Jr. is the Assistant Secretary.
    

   
                  MFS MUNICIPAL INCOME TRUST
    

   
                  Robert J. Manning is Vice President, Stephen E. Cavan is the
Secretary, W. Thomas London is the Treasurer, James O. Yost, Ellen M. Moynihan
and Mark E. Bradley are the Assistant Treasurers and James R. Bordewick, Jr. is
the Assistant Secretary.
    

   
                  MFS MULTIMARKET INCOME TRUST
                  MFS CHARTER INCOME TRUST
    

   
                  Leslie J. Nanberg and James T. Swanson are Vice Presidents,
Stephen E. Cavan is the Secretary, W. Thomas London is the Treasurer, James O.
Yost, Ellen M. Moynihan and Mark E. Bradley are the Assistant Treasurers and
James R. Bordewick, Jr. is the Assistant Secretary.
    

   
                  MFS SPECIAL VALUE TRUST
    

   
                  Robert J. Manning is Vice President, Stephen E. Cavan is the
Secretary, W. Thomas London is the Treasurer, James O. Yost, Ellen M. Moynihan
and Mark E. Bradley are the Assistant Treasurers and James R. Bordewick, Jr. is
the Assistant Secretary.
    

   
                  MFS/SUN LIFE SERIES TRUST
    

   
                  John D. McNeil, Chairman and Director of Sun Life Assurance
Company of Canada, is the Chairman, Stephen E. Cavan is the Secretary, W. Thomas
London is the Treasurer, James O. Yost, Ellen M. Moynihan and Mark E. Bradley
are the Assistant Treasurers and James R. Bordewick, Jr. is the Assistant
Secretary.
    
<PAGE>   204
   
                  MONEY MARKET VARIABLE ACCOUNT
                  HIGH YIELD VARIABLE ACCOUNT
                  CAPITAL APPRECIATION VARIABLE ACCOUNT
                  GOVERNMENT SECURITIES VARIABLE ACCOUNT
                  TOTAL RETURN VARIABLE ACCOUNT
                  WORLD GOVERNMENTS VARIABLE ACCOUNT
                  MANAGED SECTORS VARIABLE ACCOUNT
    

   
                  John D. McNeil is the Chairman, Stephen E. Cavan is the
Secretary, and James R. Bordewick, Jr. is the Assistant Secretary.
    

   
                  MIL FUNDS
    

   
                  Richard B. Bailey, John A. Brindle, Richard W. S. Baker,
Arnold D. Scott, Jeffrey L. Shames and William F. Waters are Directors, Stephen
E. Cavan is the Secretary, W. Thomas London is the Treasurer, James O. Yost,
Ellen M. Moynihan and Mark E. Bradley are the Assistant Treasurers and James R.
Bordewick, Jr. is the Assistant Secretary.
    

   
                  MFS MERIDIAN FUNDS
    

   
                  Richard B. Bailey, John A. Brindle, Richard W. S. Baker,
Arnold D. Scott, Jeffrey L. Shames and William F. Waters are Directors, Stephen
E. Cavan is the Secretary, W. Thomas London is the Treasurer, James R.
Bordewick, Jr. is the Assistant Secretary and James O. Yost, Ellen M. Moynihan
and Mark E. Bradley are the Assistant Treasurers.
    

   
                  VERTEX
    

   
                  Jeffrey L. Shames and Arnold D. Scott are the Directors,
Jeffrey L. Shames is the President, Kevin R. Parke and John W. Ballen are
Executive Vice Presidents, John F. Brennan, Jr., and John D. Laupheimer are
Senior Vice Presidents, Brian E. Stack is a Vice President, Joseph W. Dello
Russo is the Treasurer, Thomas B. Hastings is the Assistant Treasurer, Stephen
E. Cavan is the Secretary and Robert T. Burns is the Assistant Secretary.
    

   
                  MIL
    

   
                  Peter D. Laird is President and a Director, Arnold D. Scott,
Jeffrey L. Shames and Thomas J. Cashman, Jr. are Directors, Stephen E. Cavan is
a Director, Senior Vice President and the Clerk, Robert T. Burns is an Assistant
Clerk, Joseph W. Dello Russo, Executive Vice President and Chief Financial
Officer of MFS, is the Treasurer and Thomas B. Hastings is the Assistant
Treasurer.
    
<PAGE>   205
   
                  MIL-UK
    

   
                  Peter D. Laird is President and a Director, Thomas J. Cashman,
Arnold D. Scott and Jeffrey L. Shames are Directors, Stephen E. Cavan is a
Director and the Secretary, Joseph W. Dello Russo is the Treasurer, Thomas B.
Hastings is the Assistant Treasurer and Robert T. Burns is the Assistant
Secretary.
    

   
                  MFSI - AUSTRALIA
    

   
                  Thomas J. Cashman, Jr. is President and a Director, Graham E.
Lenzer, John A. Gee and David Adiseshan are Directors, Stephen E. Cavan is the
Secretary, Joseph W. Dello Russo is the Treasurer, Thomas B. Hastings is the
Assistant Treasurer, and Robert T. Burns is the Assistant Secretary.
    

   
                  MFS HOLDINGS - AUSTRALIA
    

   
                  Jeffrey L. Shames is the President and a Director, Arnold D.
Scott, Thomas J. Cashman, Jr., and Graham E. Lenzer are Directors, Stephen E.
Cavan is the Secretary, Joseph W. Dello Russo is the Treasurer, Thomas B.
Hastings is the Assistant Treasurer, and Robert T. Burns is the Assistant
Secretary.
    

   
                  MFD
    

   
                  Arnold D. Scott and Jeffrey L. Shames are Directors, William
W. Scott, Jr., an Executive Vice President of MFS, is the President, Stephen E.
Cavan is the Secretary, Robert T. Burns is the Assistant Secretary, Joseph W.
Dello Russo is the Treasurer, and Thomas B. Hastings is the Assistant Treasurer.
    

   
                  MFSC
    

   
                  Arnold D. Scott and Jeffrey L. Shames are Directors, Joseph A.
Recomendes, a Senior Vice President and Chief Information Officer of MFS, is
Vice Chairman and a Director, Janet A. Clifford is the President, Joseph W.
Dello Russo is the Treasurer, Thomas B. Hastings is the Assistant Treasurer,
Stephen E. Cavan is the Secretary, and Robert T. Burns is the Assistant
Secretary.
    

   
                  MFSI
    

   
                  Thomas J. Cashman, Jr., Jeffrey L. Shames, and Arnold D. Scott
are Directors, Joseph J. Trainor is the President and a Director, Leslie J.
Nanberg is a Senior Vice President, a Managing Director and a Director, Kevin R.
Parke is the Executive Vice President and a Managing Director, George F.
Bennett, Jr., John A. Gee, Brianne Grady, Joseph A. Kosciuszek and Joseph J.
Trainor are Senior Vice Presidents and Managing Directors, Joseph W. Dello Russo
is the Treasurer, Thomas B. Hastings is the Assistant Treasurer and Robert T.
Burns is the Secretary.
    
<PAGE>   206
   
                  RSI
    

   
                  Arnold D. Scott is the Chairman and a Director, Martin E.
Beaulieu is the President, William W. Scott, Jr. is a Director, Joseph W. Dello
Russo is the Treasurer, Thomas B. Hastings is the Assistant Treasurer, Stephen
E. Cavan is the Secretary and Robert T. Burns is the Assistant Secretary.
    

   
                  In addition, the following persons, Directors or officers of
MFS, have the affiliations indicated:
    

   
                  Donald A. Stewart         President and a Director, Sun Life
                                             Assurance Company of Canada, Sun
                                             Life Centre, 150 King Street West,
                                             Toronto, Ontario, Canada (Mr.
                                             Stewart is also an officer and/or
                                             Director of various subsidiaries
                                             and affiliates of Sun Life)



                  John D. McNeil           Chairman, Sun Life Assurance
                                             Company of Canada, Sun Life Centre,
                                             150 King Street West, Toronto,
                                             Ontario, Canada (Mr. McNeil is also
                                             an officer and/or Director of
                                             various subsidiaries and affiliates
                                             of Sun Life)



                  Joseph W. Dello Russo    Director of Mutual Fund Operations,
                                             The Boston Company, Exchange Place,
                                             Boston, Massachusetts (until
                                             August, 1994)
    



ITEM 28.          DISTRIBUTORS

                  (a) Reference is hereby made to Item 27 above.

                  (b) Reference is hereby made to Item 27 above; the principal
business address of each of these persons is 500 Boylston Street, Boston,
Massachusetts 02116.

                  (c) Not applicable.

ITEM 29.          LOCATION OF ACCOUNTS AND RECORDS

                  The accounts and records of the Registrant are located, in
whole or in part, at the office of the Registrant and the following locations:

                        NAME                                 ADDRESS
                        ----                                 -------

          Massachusetts Financial Services              500 Boylston Street
           Company (investment adviser)                 Boston, MA  02116
<PAGE>   207
          MFS Fund Distributors, Inc.                   500 Boylston Street
           (principal underwriter)                      Boston, MA  02116

          State Street Bank and Trust Company           State Street South
           (custodian)                                  5-West
                                                        North Quincy, MA  02171

          MFS Service Center, Inc.                      500 Boylston Street
           (transfer agent)                             Boston, MA  02116

ITEM 30.          MANAGEMENT SERVICES

                  Not Applicable.

ITEM 31.          UNDERTAKINGS

                  (a)    Not Applicable.

                  (b)    Not Applicable.

                  (c) Registrant undertakes to furnish each person to whom a
prospectus is delivered with a copy of its latest annual report to shareholders
upon request and without charge.

                  (d) Insofar as indemnification for liability arising under the
Securities Act of 1933 may be permitted to trustees, officers and controlling
persons of the Registrant pursuant to the provisions set forth in Item 26 of
this Part C, or otherwise, the Registrant has been advised that in the opinion
of the Securities and Exchange Commission such indemnification is against public
policy as expressed in the Act and is, therefore, unenforceable. In the event
that a claim for indemnification against such liabilities (other than the
payment by the Registrant of expenses incurred or paid by a trustee, officer or
controlling person of the Registrant in the successful defense of any action,
suit or proceeding) is asserted by such director, officer or controlling person
in connection with the Securities being registered, the Registrant will, unless
in the opinion of its counsel the matter has been settled by controlling
precedent, submit to a court of appropriate jurisdiction the question whether
such indemnification by it is against public policy as expressed in the Act and
will be governed by the final adjudication of such issues.
<PAGE>   208
                                   SIGNATURES


      Pursuant to the requirements of the Securities Act of 1933 and the
Investment Company Act of 1940, the Registrant certifies that it meets all of
the requirements for effectiveness of this Registration Statement pursuant to
Rule 485(b) under the Securities Act of 1933 and has duly caused this
Post-Effective Amendment to the Registration Statement to be signed on its
behalf by the undersigned, thereto duly authorized, in the City of Boston and
The Commonwealth of Massachusetts on the 16th day of November, 1998.

                                               MFS SERIES TRUST IV


                                               By:      JAMES R. BORDEWICK, JR.
                                                       ------------------------
                                               Name:    James R. Bordewick, Jr.
                                               Title:   Assistant Secretary

      Pursuant to the requirements of the Securities Act of 1933, this
Post-Effective Amendment to its Registration Statement has been signed below by
the following persons in the capacities indicated on November 16, 1998.

       SIGNATURE                                      TITLE
       ---------                                      -----


STEPHEN E. CAVAN*                      Principal Executive Officer
- --------------------------------
Stephen E. Cavan


W. THOMAS LONDON*                      Treasurer (Principal Financial Officer
- --------------------------------        and Principal Accounting Officer)
W. Thomas London


RICHARD B. BAILEY*                     Trustee
- --------------------------------
Richard B. Bailey


PETER G. HARWOOD*                      Trustee
- --------------------------------
Peter G. Harwood


J. ATWOOD IVES*                        Trustee
- --------------------------------
J. Atwood Ives
<PAGE>   209
LAWRENCE T. PERERA*                                    Trustee
- --------------------------------
Lawrence T. Perera


WILLIAM J. POORVU*                                     Trustee
- --------------------------------
William J. Poorvu


CHARLES W. SCHMIDT*                                    Trustee
- --------------------------------
Charles W. Schmidt


ARNOLD D. SCOTT*                                       Trustee
- --------------------------------
Arnold D. Scott


JEFFREY L. SHAMES*                                     Trustee
- --------------------------------
Jeffrey L. Shames


ELAINE R. SMITH*                                       Trustee
- --------------------------------
Elaine R. Smith


DAVID B. STONE*                                        Trustee
- --------------------------------
David B. Stone


                                        *By:       JAMES R. BORDEWICK, JR.
                                        Name:      James R. Bordewick, Jr.
                                                      as Attorney-in-fact

                                         Executed by James R. Bordewick, Jr., on
                                         behalf of those indicated pursuant to
                                         (i) a Power of Attorney dated September
                                         21, 1994, filed electronically with the
                                         Securities and Exchange Commission on
                                         February 28, 1995 and (ii) a Power of
                                         Attorney dated February 19, 1998; filed
                                         herewith.
<PAGE>   210
                                POWER OF ATTORNEY

                               MFS Series Trust IV


         The undersigned officer of MFS Series Trust IV (the "Registrant")
hereby severally constitutes and appoints Jeffrey L. Shames, Arnold D. Scott, W.
Thomas London, and James R. Bordewick, Jr., and each of them singly, as true and
lawful attorneys, with full power to them and each of them to sign for the
undersigned, in the name of, and in the capacity indicated below, any
Registration Statement and any and all amendments thereto and to file the same
with all exhibits thereto, and other documents in connection therewith, with the
Securities and Exchange Commission for the purpose of registering the Registrant
as a management investment company under the Investment Company Act of 1940
and/or the shares issued by the Registrant under the Securities Act of 1933
granting unto my said attorneys, and each of them, acting alone, full power and
authority to do and perform each and every act and thing requisite or necessary
or desirable to be done in the premises, as fully to all intents and purposes as
he or she might or could do in person, hereby ratifying and confirming all that
said attorneys or any of them may lawfully do or cause to be done by virtue
thereof.

         In WITNESS WHEREOF, the undersigned has hereunto set his hand on this
19th day of February, 1998.


         Signature                          Title
         ---------                          -----

         STEPHEN E. CAVAN                   Principal Executive Officer
         ---------------------------
         Stephen E. Cavan
<PAGE>   211
                                INDEX TO EXHIBITS


EXHIBIT NO.      DESCRIPTION OF EXHIBIT                             PAGE NO.
- -----------      ----------------------                             --------

      1    (c)   Amendment to Declaration of Trust, dated
                 August 29, 1997.

      9    (b)   Amendment to Shareholder Servicing Agreement
                 dated January 1, 1998 to amend Fee Schedule.

     11          Consent of Deloitte & Touche LLP.

     17          Financial Data Schedules for each class of each
                 series.

<PAGE>   1
                                                             EXHIBIT NO. 99.1(c)


                               MFS SERIES TRUST IV

                           CERTIFICATION OF AMENDMENT
                           TO THE DECLARATION OF TRUST

                             REDESIGNATION OF SERIES


         The undersigned, being a majority of the Trustees of MFS Series Trust
IV (the "Trust"), a business trust organized under the laws of The Commonwealth
of Massachusetts pursuant to an Amended and Restated Declaration of Trust dated
December 21, 1994, as amended (the "Declaration"), acting pursuant to Section
6.9 of the Declaration, do hereby redesignate an existing series of Shares (as
defined in the Declaration) as follows:



         1.       The series designated as MFS OTC Fund shall be redesignated as
                  MFS Mid-Cap Growth Fund.

         Pursuant to Section 6.9(i) of the Declaration, this redesignation of
series of Shares shall be effective upon the execution of a majority of the
Trustees of the Trust.

<PAGE>   2
      IN WITNESS WHEREOF, a majority of the Trustees of the Trust have executed
this amendment, in one or more counterparts, all constituting a single
instrument, as an instrument under seal in The Commonwealth of Massachusetts, as
of this 29th day of August, 1997.



A. KEITH BRODKIN                                   CHARLES W. SCHMIDT
- ------------------------                           -------------------------
A. Keith Brodkin                                   Charles W. Schmidt
76 Farm Road                                       63 Claypit Hill Road
Sherborn, MA  01770                                Wayland, MA  01778



RICHARD B. BAILEY
- ------------------------                           -------------------------
Richard B. Bailey                                  Arnold D. Scott
63 Atlantic Avenue                                 20 Rowes Wharf
Boston, MA  02110                                  Boston, MA  02110



PETER G. HARWOOD
- ------------------------                           -------------------------
Peter G. Harwood                                   Jeffrey L. Shames
211 Lindsay Pond Road                              38 Lake Avenue
Concord, MA  01742                                 Newton, MA  02159



J. ATWOOD IVES                                     ELAINE R. SMITH
- ------------------------                           -------------------------
J. Atwood Ives                                     Elaine R. Smith
1 Bennington Road                                  75 Scotch Pine Road
Lexington, MA  02173                               Weston, MA  02193



LAWRENCE T. PERERA                                 DAVID B. STONE
- ------------------------                           -------------------------
Lawrence T. Perera                                 David B. Stone
18 Marlborough Street                              282 Beacon Street
Boston, MA  02116                                  Boston, MA  02116



WILLIAM J. POORVU
- ------------------------
William J. Poorvu
975 Memorial Drive
Cambridge, MA  02138




<PAGE>   1
                                                             EXHIBIT NO. 99.9(b)


                               MFS SERIES TRUST IV
              500 BOYLSTON STREET - BOSTON - MASSACHUSETTS - 02116
                                (617) - 954-5000



                                                                 January 1, 1998




MFS Service Center, Inc.
500 Boylston Street
Boston, MA 02116

Dear Sir/Madam:

         This will confirm our understanding that Exhibit B to the Shareholder
Servicing Agent Agreement between us, dated August 1, 1985, as amended, is
hereby amended, effective immediately, to read in its entirety as set forth on
Attachment 1 hereto.

         Please indicate your acceptance of the foregoing by signing below.

                                                      Sincerely,

                                                      MFS SERIES TRUST IV




                                                      By: W. THOMAS LONDON
                                                          ----------------------
                                                          W. Thomas London
                                                          Treasurer


Accepted and Agreed:

MFS SERVICE CENTER, INC.



By: JOSEPH W. DELLO RUSSO
    ----------------------
     Joseph W. Dello Russo
     Treasurer
<PAGE>   2
                                                                    ATTACHMENT 1
                                                                 January 1, 1998


                          EXHIBIT B TO THE SHAREHOLDER
                        SERVICING AGENT AGREEMENT BETWEEN
                        MFS SERVICE CENTER, INC. ("MFSC")
                      AND MFS SERIES TRUST IV (THE "FUND")


The fees to be paid by the Fund on behalf of its series with respect to all
shares of each series of the Fund to MFSC, for MFSC's services as shareholder
servicing agent, shall be 0.1125% of the average daily net assets of the Fund.

<PAGE>   1
                                                                   EXHIBIT 99.11



                          INDEPENDENT AUDITORS' CONSENT



         We consent to the incorporation by reference in this Post-Effective
Amendment No. 33 to Registration Statement No. 2-54607 of MFS Series Trust IV,
of our reports each dated October 9, 1998, appearing in the annual reports to
shareholders for the year ended August 31, 1998, of MFS Money Market Fund and
MFS Government Money Market Fund, MFS Municipal Bond Fund and MFS Mid Cap Growth
Fund (formerly MFS OTC Fund), each a series of MFS Series Trust IV, and to the
references to us under the headings "Condensed Financial Information" in each
Prospectus and "Independent Auditors and Financial Statements" in each Statement
of Additional Information, which are part of such Registration Statement.



DELOITTE & TOUCHE LLP
Deloitte & Touche LLP


Boston, Massachusetts
November 24, 1998

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<NAME> MFS SERIES TRUST IV
<SERIES>
   <NUMBER> 042
   <NAME> MFS MID CAP GROWTH FUND - CLASS B
<MULTIPLIER> 1
       
<S>                             <C>
<PERIOD-TYPE>                   12-MOS
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<PERIOD-START>                             SEP-01-1997
<PERIOD-END>                               AUG-31-1998
<INVESTMENTS-AT-COST>                        123392627
<INVESTMENTS-AT-VALUE>                        99274275
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</TABLE>

<TABLE> <S> <C>


<ARTICLE> 6
<CIK> 0000063068
<NAME> MFS SERIES TRUST IV
<SERIES>
   <NUMBER> 043
   <NAME> MFS MID CAP GROWTH FUND - CLASS C
<MULTIPLIER> 1
       
<S>                             <C>
<PERIOD-TYPE>                   12-MOS
<FISCAL-YEAR-END>                          AUG-31-1998
<PERIOD-START>                             SEP-01-1997
<PERIOD-END>                               AUG-31-1998
<INVESTMENTS-AT-COST>                        123392627
<INVESTMENTS-AT-VALUE>                        99274275
<RECEIVABLES>                                  2941897
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<TOTAL-ASSETS>                               102229964
<PAYABLE-FOR-SECURITIES>                       1957954
<SENIOR-LONG-TERM-DEBT>                              0
<OTHER-ITEMS-LIABILITIES>                      1228767
<TOTAL-LIABILITIES>                            3186721
<SENIOR-EQUITY>                                      0
<PAID-IN-CAPITAL-COMMON>                     110042073
<SHARES-COMMON-STOCK>                           744654
<SHARES-COMMON-PRIOR>                           630395
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<OVERDISTRIBUTION-NII>                         (14911)
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<APPREC-INCREASE-CURRENT>                   (35717948)
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<DISTRIBUTIONS-OF-GAINS>                      (131365)
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<NUMBER-OF-SHARES-REDEEMED>                   (428913)
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<OVERDISTRIB-NII-PRIOR>                         (9435)
<OVERDIST-NET-GAINS-PRIOR>                    (582892)
<GROSS-ADVISORY-FEES>                           972215
<INTEREST-EXPENSE>                                2101
<GROSS-EXPENSE>                                2472978
<AVERAGE-NET-ASSETS>                         129583291
<PER-SHARE-NAV-BEGIN>                             9.19
<PER-SHARE-NII>                                 (0.18)
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<AVG-DEBT-PER-SHARE>                                 0
        


</TABLE>

<TABLE> <S> <C>


<ARTICLE> 6
<CIK> 0000063068
<NAME> MFS SERIES TRUST IV
<SERIES>
   <NUMBER> 044
   <NAME> MFS MID CAP GROWTH FUND - CLASS I
<MULTIPLIER> 1
       
<S>                             <C>
<PERIOD-TYPE>                   12-MOS
<FISCAL-YEAR-END>                          AUG-31-1998
<PERIOD-START>                             SEP-01-1997
<PERIOD-END>                               AUG-31-1998
<INVESTMENTS-AT-COST>                        123392627
<INVESTMENTS-AT-VALUE>                        99274275
<RECEIVABLES>                                  2941897
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<PAYABLE-FOR-SECURITIES>                       1957954
<SENIOR-LONG-TERM-DEBT>                              0
<OTHER-ITEMS-LIABILITIES>                      1228767
<TOTAL-LIABILITIES>                            3186721
<SENIOR-EQUITY>                                      0
<PAID-IN-CAPITAL-COMMON>                     110042073
<SHARES-COMMON-STOCK>                           119708
<SHARES-COMMON-PRIOR>                           146676
<ACCUMULATED-NII-CURRENT>                            0
<OVERDISTRIBUTION-NII>                         (14911)
<ACCUMULATED-NET-GAINS>                       13134433
<OVERDISTRIBUTION-GAINS>                             0
<ACCUM-APPREC-OR-DEPREC>                    (24118352)
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<DIVIDEND-INCOME>                               272188
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<EXPENSES-NET>                               (2460404)
<NET-INVESTMENT-INCOME>                      (2000225)
<REALIZED-GAINS-CURRENT>                      18745576
<APPREC-INCREASE-CURRENT>                   (35717948)
<NET-CHANGE-FROM-OPS>                       (18972597)
<EQUALIZATION>                                       0
<DISTRIBUTIONS-OF-INCOME>                            0
<DISTRIBUTIONS-OF-GAINS>                       (38088)
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<NUMBER-OF-SHARES-SOLD>                          18237
<NUMBER-OF-SHARES-REDEEMED>                    (49523)
<SHARES-REINVESTED>                               4318
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<OVERDISTRIB-NII-PRIOR>                         (9435)
<OVERDIST-NET-GAINS-PRIOR>                    (582892)
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<INTEREST-EXPENSE>                                2101
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<AVERAGE-NET-ASSETS>                         129583291
<PER-SHARE-NAV-BEGIN>                             9.44
<PER-SHARE-NII>                                 (0.08)
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</TABLE>


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