MFS VARIABLE INSURANCE TRUST
497, 1997-05-05
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<PAGE>
 
<TABLE>
<S>                                         <C>
MFS-REGISTERED TRADEMARK- EMERGING GROWTH
SERIES
MFS-REGISTERED TRADEMARK- RESEARCH SERIES
MFS-REGISTERED TRADEMARK- TOTAL RETURN
SERIES
MFS-REGISTERED TRADEMARK- UTILITIES SERIES
MFS-REGISTERED TRADEMARK- WORLD
GOVERNMENTS SERIES                          PROSPECTUS
MFS-REGISTERED TRADEMARK- BOND SERIES       May 1, 1997
</TABLE>
 
- --------------------------------------------------------------------------------
 
<TABLE>
<S>                                                              <C>                     <S>                           <C>
MFS-Registered Trademark- VARIABLE INSURANCE TRUST-SM-
</TABLE>
 
MFS  Variable Insurance Trust (the "Trust") is an open-end management investment
company offering insurance company separate  accounts a selection of  investment
vehicles  for  variable  annuity  and  variable  life  insurance  contracts (the
"Contracts"). Currently the  Trust offers  shares of beneficial  interest of  12
separate  mutual fund series (individually  or collectively hereinafter referred
to as a "Series"  or the "Series"),  six of which are  offered pursuant to  this
Prospectus:
 
- -- MFS  EMERGING GROWTH  SERIES (the "Emerging  Growth Series"),  which seeks to
   provide long-term growth of capital;
 
- -- MFS RESEARCH SERIES (the "Research Series"), which seeks to provide long-term
   growth of capital and future income;
 
- -- MFS TOTAL RETURN SERIES (the "Total Return Series"), which seeks primarily to
   provide above-average income  (compared to a  portfolio invested entirely  in
   equity  securities)  consistent with  the prudent  employment of  capital and
   secondarily to provide  a reasonable  opportunity for growth  of capital  and
   income;
 
- -- MFS UTILITIES SERIES (the "Utilities Series"), which seeks capital growth and
   current  income  (income  above  that  available  from  a  portfolio invested
   entirely in equity securities);
 
- -- MFS WORLD GOVERNMENTS  SERIES (the "World  Governments Series"), which  seeks
   not  only preservation  but also  growth of  capital, together  with moderate
   current income; and
 
- -- MFS BOND SERIES (the "Bond Series"), which seeks primarily to provide as high
   a level of current income as  is believed consistent with prudent  investment
   risk, and secondarily to protect shareholders' capital.
                              -------------------
 
THE  EMERGING GROWTH SERIES  AND THE RESEARCH SERIES  ARE INTENDED FOR INVESTORS
WHO UNDERSTAND AND ARE WILLING TO ACCEPT THE RISKS ENTAILED IN SEEKING LONG-TERM
GROWTH OF CAPITAL. BECAUSE OF THEIR INVESTMENT POLICIES PERMITTING INVESTMENT IN
FOREIGN SECURITIES,  INVESTMENTS IN  EACH SERIES  MAY BE  SUBJECT TO  A  GREATER
DEGREE  OF  RISK THAN  INVESTMENTS IN  OTHER  INVESTMENT COMPANIES  WHICH INVEST
ENTIRELY IN DOMESTIC SECURITIES.
                              -------------------
 
  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.
                              -------------------
 
SHARES OF THE TRUST  ARE AVAILABLE AND  ARE BEING MARKETED  AS A POOLED  FUNDING
VEHICLE FOR LIFE INSURANCE COMPANIES WRITING ALL TYPES OF CONTRACTS.
 
This  Prospectus sets forth  concisely the information about  each Series that a
prospective investor should know  before applying for  the Contracts offered  by
the  separate accounts of certain  insurance companies ("Participating Insurance
Companies"). Investors are advised  to read this  Prospectus and the  applicable
Contract  prospectus  carefully and  retain them  for  future reference.  If you
require more detailed information, a  Statement of Additional Information  dated
May  1,  1997, as  amended or  supplemented from  time to  time (the  "SAI"), is
available upon  request without  charge and  may be  obtained by  calling or  by
writing to the Shareholder Servicing Agent (see back cover for address and phone
number).  The SAI, which is incorporated  by reference into this Prospectus, has
been filed with  the Securities  and Exchange  Commission (the  "SEC"). The  SEC
maintains  an Internet World Wide Web site that contains the SAI, materials that
are incorporated  by reference  into  this Prospectus  and  the SAI,  and  other
information  regarding the Series. This Prospectus is available on the Adviser's
Internet World Wide Web site at http://www.mfs.com.
 
   INVESTORS SHOULD READ THIS PROSPECTUS AND RETAIN IT FOR FUTURE REFERENCE.
<PAGE>
TABLE OF CONTENTS
 
<TABLE>
<CAPTION>
                                                                                                       PAGE
                                                                                                       ---
  <S>                                                                                                  <C>
  1.  Expense Summary................................................................................   3
  2.  Investment Concept of the Trust................................................................   3
  3.  Condensed Financial Information................................................................   5
  4.  Investment Objectives and Policies.............................................................  11
      MFS Emerging Growth Series.....................................................................  11
      MFS Research Series............................................................................  11
      MFS Total Return Series........................................................................  12
      MFS Utilities Series...........................................................................  12
      MFS World Governments Series...................................................................  14
      MFS Bond Series................................................................................  15
  5.  Investment Techniques..........................................................................  15
  6.  Additional Risk Factors........................................................................  21
  7.  Management of the Series.......................................................................  24
  8.  Information Concerning Shares of Each Series...................................................  27
      Purchases and Redemptions......................................................................  27
      Net Asset Value................................................................................  27
      Distributions..................................................................................  27
      Tax Status.....................................................................................  27
      Description of Shares, Voting Rights and Liabilities...........................................  28
      Performance Information........................................................................  28
      Expenses.......................................................................................  29
      Shareholder Communications.....................................................................  29
  Appendix A -- Description of Bond Ratings..........................................................  A-1
  Appendix B -- Principal Sectors of the Utilities Industry..........................................  B-1
  Appendix C -- Portfolio Composition Charts.........................................................  C-1
</TABLE>
 
                                       2
<PAGE>
1.  EXPENSE SUMMARY
 
ANNUAL OPERATING EXPENSES (AS A PERCENTAGE OF AVERAGE NET ASSETS):
<TABLE>
<CAPTION>
                                                                MFS
                                                              EMERGING     MFS
                                                               GROWTH    RESEARCH
                                                               SERIES     SERIES
                                                              --------   --------
<S>                                                           <C>        <C>
Management Fee..............................................  0.75%      0.75%
Other Expenses (after expense limitation)(1)(2).............  0.25%      0.25%
                                                              --------   --------
Total Operating Expenses (after expense limitation)(2)......  1.00%      1.00%
 
<CAPTION>
 
                                                                MFS
                                                               TOTAL       MFS
                                                               RETURN    UTILITIES
                                                               SERIES     SERIES
                                                              --------   --------
<S>                                                           <C>        <C>
Management Fee..............................................  0.75%      0.75%
Other Expenses (after expense limitation)(1)(2).............  0.25%      0.25%
                                                              --------   --------
Total Operating Expenses (after expense limitation)(2)......  1.00%      1.00%
<CAPTION>
 
                                                                           MFS
                                                                          WORLD
                                                              MFS BOND   GOVERNMENTS
                                                               SERIES     SERIES
                                                              --------   --------
<S>                                                           <C>        <C>
Management Fee..............................................  0.60%      0.75%
Other Expenses (after expense limitation)(1)(2).............  0.40%      0.25%
                                                              --------   --------
Total Operating Expenses (after expense limitation)(2)......  1.00%      1.00%
<FN>
- ------------------------
(1)        Each  Series has an expense offset arrangement which reduces the Series' custodian fee based upon the amount of cash
           maintained by  the  Series  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 Series'
           expenses). Any such fee reductions are not reflected under "Other Expenses."
(2)        The Adviser has agreed to bear expenses for each Series, subject to reimbursement by each Series, such that each
           Series' "Other Expenses" shall not exceed the following percentages of the average daily net assets of the Series
           during the current fiscal year: 0.40% for the Bond Series, and 0.25% for each remaining Series. See "Information
           Concerning Shares of Each Series--Expenses." Otherwise, "Other Expenses" and "Total Operating Expenses" for each
           Series would be:
</TABLE>
 
<TABLE>
<CAPTION>
                                                                      "TOTAL OPERATING
                                             "OTHER EXPENSES"             EXPENSES"
                                                  WITHOUT                  WITHOUT
SERIES                                      EXPENSE LIMITATION       EXPENSE LIMITATION
- -----------------------------------------  ---------------------  -------------------------
<S>                                        <C>                    <C>
Emerging Growth..........................             0.41%                    1.16%
Research.................................             0.73%                    1.48%
Total Return.............................             1.35%                    2.10%
Utilities................................             2.00%                    2.75%
World Governments........................             1.28%                    2.03%
Bond.....................................             8.85%                    9.45%
</TABLE>
 
    The  purpose  of  the  expense  table  above  is  to  assist  investors   in
understanding  the various costs  and expenses that a  shareholder of the Series
will bear directly or indirectly. The  Series' annual operating expenses do  not
reflect  expenses  imposed  by  separate  accounts  of  Participating  Insurance
Companies through  which an  investment in  a Series  is made  or their  related
Contracts. A separate account's expenses are disclosed in the prospectus through
which the Contract relating to that separate account is offered for sale.
 
2.  INVESTMENT CONCEPT OF THE TRUST
 
    The Trust is an open-end, registered management investment company comprised
of  the following twelve series: Emerging  Growth Series, Value Series, Research
Series, Growth With Income Series,  Total Return Series, Utilities Series,  High
Income  Series, World  Governments Series,  Strategic Fixed  Income Series, Bond
Series, Limited  Maturity Series  and  Money Market  Series.  Each Series  is  a
segregated,  separately  managed portfolio  of  securities. All  of  the Series,
except the Utilities Series, World Governments Series and Strategic Fixed Income
Series, are diversified. Additional series may be created from time to time. The
Trust was organized as a  business trust under the  laws of The Commonwealth  of
Massachusetts by a Declaration of Trust dated February 1, 1994.
 
                                       3
<PAGE>
    The  Trust  currently  offers shares  of  each Series  to  insurance company
separate accounts that fund Contracts. Separate accounts may purchase or  redeem
shares  at net  asset value  without any  sales or  redemption charge.  Fees and
charges imposed by a separate account, however, will affect the actual return to
the  holder  of  a  Contract.  A  separate  account  may  also  impose   certain
restrictions  or limitations on the allocation  of purchase payments or Contract
value to one or more Series, and  not all Series may be available in  connection
with  a particular Contract. Prospective investors should consult the applicable
Contract prospectus for information regarding fees and expenses of the  Contract
and  separate account and any applicable  restrictions or limitations. The Trust
assumes no responsibility for such prospectuses.
 
    Shares of the Series are offered  to the separate accounts of  Participating
Insurance  Companies  that are  affiliated  or unaffiliated  ("shared funding").
Shares of the Series may serve  as the underlying investments for both  variable
annuity  and  variable  life  insurance  contracts  ("mixed  funding").  Due  to
differences in tax treatment or  other considerations, the interests of  various
Contract  owners might at some time be in conflict. The Trust currently does not
foresee any such conflict. Nevertheless, the Trust's Trustees intend to  monitor
events  in order  to identify  any material  irreconcilable conflicts  which may
possibly arise and to determine what action, if any, should be taken in response
thereto. If such a conflict were to occur, one or more separate accounts of  the
Participating  Insurance Companies might be required to withdraw its investments
in one one  or more  Series. This  might force a  Series to  sell securities  at
disadvantageous prices.
 
    Individual Contract holders are not the "shareholders" of the Trust. Rather,
the  Participating  Insurance  Companies  and their  separate  accounts  are the
shareholders or  investors,  although such  companies  may pass  through  voting
rights to their Contract holders.
 
    The Trust's Board of Trustees provides broad supervision over the affairs of
the  Trust and the Series. Massachusetts  Financial Services Company, a Delaware
corporation ("MFS" or the "Adviser"), is the investment adviser to each  Series.
A majority of the Trustees of the Trust are not affiliated with the Adviser. The
Adviser  is responsible for the management of  the assets of each Series and the
officers of the Trust  are responsible for the  operations. The Adviser  manages
the  Series'  portfolios  from day  to  day  in accordance  with  the investment
objectives and policies of each Series. The selection of investments and the way
they are managed  depend on the  conditions and  trends in the  economy and  the
financial marketplaces.
 
                                       4
<PAGE>
3.  CONDENSED FINANCIAL INFORMATION
 
    The  following financial information has been audited since the commencement
of investment operations of such Series  and should be read in conjunction  with
the financial statements included in the Series' Annual Reports to Shareholders.
These  financial  statements  are  incorporated by  reference  into  the  SAI in
reliance upon the report  of the Series' independent  auditors given upon  their
authority as experts in accounting and auditing. The Series' current independent
auditors are Deloitte & Touche LLP.
 
                             EMERGING GROWTH SERIES
 
<TABLE>
<CAPTION>
                                                                      YEAR ENDED          PERIOD ENDED
                                                                   DECEMBER 31, 1996   DECEMBER 31, 1995*
                                                                   -----------------   ------------------
<S>                                                                <C>                 <C>
Per share data (for a share outstanding throughout each period):
Net asset value--beginning of period.............................      $  11.41             $10.00
                                                                       --------             ------
Income from investment operations#--
  Net investment income (loss)Section............................      $  (0.01)            $ 0.01
  Net realized and unrealized gain on investments and foreign
    currency transactions........................................          1.95               1.74
                                                                       --------             ------
    Total from investment operations.............................      $   1.94             $ 1.75
                                                                       --------             ------
Less distributions declared to shareholders--
  From net investment income.....................................      $     --             $(0.01)
  From net realized gain on investments and foreign currency
    transactions.................................................         (0.06)             (0.26)
  In excess of net realized gain on investments and foreign
    currency transactions........................................         (0.05)                --
  Tax return of capital..........................................            --              (0.07)
                                                                       --------             ------
    Total distributions declared to shareholders.................      $  (0.11)            $(0.34)
                                                                       --------             ------
Net asset value--end of period...................................      $  13.24             $11.41
                                                                       --------             ------
                                                                       --------             ------
Total return.....................................................         17.02%             17.41%++
Ratios (to average net assets)/Supplemental dataSection:
  Expenses.......................................................          1.00%              1.00%+
  Net investment income (loss)...................................         (0.08)%             0.10%+
Portfolio turnover...............................................            96%                73%
Average commission rate###.......................................      $ 0.0401                 --
Net assets at end of period (000 omitted)........................      $104,956             $3,869
- ---------
        * For the period from the commencement of investment operations, July 24, 1995 to December 31, 1995.
        +  Annualized.
       ++  Not annualized.
        #  Per share data is based on average shares outstanding.
      ###  Average commission rate is calculated for Series' with fiscal years beginning on or after September 1, 1995.
  Section  The  Adviser voluntarily agreed to maintain the  expenses of the Series at not  more than 1.00% of average daily
           net assets. To the extent actual expenses were over these limitations, the net investment loss per share and the
           ratios would have been:
 
Net investment loss..............................................         $(0.03)           $(0.18)
Ratios (to average net assets):
  Expenses.......................................................           1.16%             2.91%+
  Net investment loss............................................          (0.23)%           (1.78)%+
</TABLE>
 
                                       5
<PAGE>
                                RESEARCH SERIES
 
<TABLE>
<CAPTION>
                                                                       YEAR ENDED           PERIOD ENDED
                                                                    DECEMBER 31, 1996    DECEMBER 31, 1995*
                                                                   -------------------   ------------------
<S>                                                                <C>                   <C>
Per share data (for a share outstanding throughout each period):
Net asset value--beginning of period.............................        $ 10.89               $10.00
                                                                         -------               ------
Income from investment operations#--
  Net investment incomeSection...................................        $  0.06               $ 0.05
  Net realized and unrealized gain on investments and foreign
    currency transactions........................................           2.37                 1.01
                                                                         -------               ------
    Total from investment operations.............................        $  2.43               $ 1.06
                                                                         -------               ------
Less distributions declared to shareholders--
  From net investment income.....................................        $ (0.02)              $(0.03)
  From net realized gain on investments and foreign currency
    transactions.................................................          (0.16)               (0.14)
  In excess of net realized gain on investments and foreign
    currency transactions........................................          (0.01)                  --
                                                                         -------               ------
    Total distributions declared to shareholders.................        $ (0.19)              $(0.17)
                                                                         -------               ------
Net asset value--end of period...................................        $ 13.13               $10.89
                                                                         -------               ------
                                                                         -------               ------
Total return.....................................................          22.33%               10.62%++
Ratios (to average net assets)/Supplemental dataSection:
  Expenses.......................................................           1.00%                1.00%+
  Net investment income..........................................           0.47%                1.15%+
Portfolio turnover...............................................             56%                  28%
Average commission rate###.......................................        $0.0295                   --
Net assets at end of period (000 omitted)........................        $35,710               $2,530
<FN>
- ------------------------
        *  For the period from the commencement of investment operations, July 26, 1995 to December 31, 1995.
        +  Annualized.
       ++  Not annualized.
        #  Per share data is based on average shares outstanding.
      ###  Average commission rate is calculated for funds with fiscal years beginning on or after September 1, 1995.
  Section  The Adviser voluntarily agreed to maintain  the expenses of the Series at  not more than 1.00% of average  daily
           net assets. To the extent actual expenses were over these limitations, the net investment loss per share and the
           ratios would have been:
 
Net investment loss..............................................               --           $(0.08)
Ratios (to average net assets):
  Expenses.......................................................             1.48%            3.90%+
  Net investment loss............................................               --            (1.73)%+
</TABLE>
 
                                       6
<PAGE>
                              TOTAL RETURN SERIES
 
<TABLE>
<CAPTION>
                                                                       YEAR ENDED           PERIOD ENDED
                                                                    DECEMBER 31, 1996    DECEMBER 31, 1995*
                                                                   -------------------   ------------------
<S>                                                                <C>                   <C>
Per share data (for a share outstanding throughout each period):
Net asset value--beginning of period.............................        $ 12.25               $10.00
                                                                         -------               ------
Income from investment operations#--
  Net investment incomeSection...................................        $  0.46               $ 0.41
  Net realized and unrealized gain on investments and foreign
    currency transactions........................................           1.30                 2.32
                                                                         -------               ------
    Total from investment operations.............................        $  1.76               $ 2.73
                                                                         -------               ------
Less distributions declared to shareholders--
  From net investment income.....................................        $ (0.21)              $(0.25)
  From net realized gain on investments and foreign currency
    transactions.................................................          (0.09)               (0.23)
                                                                         -------               ------
    Total distributions declared to shareholders.................        $ (0.30)              $(0.48)
                                                                         -------
Net asset value--end of period...................................        $ 13.71               $12.25
                                                                         -------               ------
                                                                         -------               ------
Total return.....................................................          14.37%               27.34%++
Ratios (to average net assets)/Supplemental dataSection:
  Expenses.......................................................           1.00%                1.00%+
  Net investment income..........................................           3.59%                3.83%+
Portfolio turnover...............................................             76%                  16%
Average commission rate###.......................................        $0.0485                   --
Net assets at end of period (000 omitted)........................        $19,250               $2,797
<FN>
- ------------------------
        *  For the period from the commencement of investment operations, January 3, 1995 to December 31, 1995.
        +  Annualized.
       ++  Not annualized.
        #  Per share data is based on average shares outstanding.
      ###  Average commission rate is calculated for funds with fiscal years beginning on or after September 1, 1995.
  Section  The  Adviser voluntarily agreed to maintain the  expenses of the Series at not  more than 1.00% of average daily
           net assets. To the extent actual expenses were over  these limitations, the net investment income per share  and
           the ratios would have been:
 
Net investment income............................................            $0.32             $0.22
Ratios (to average net assets):
  Expenses.......................................................             2.10%             2.49%+
  Net investment income..........................................             2.49%             2.09%+
</TABLE>
 
                                       7
<PAGE>
                                UTILITIES SERIES
 
<TABLE>
<CAPTION>
                                                                       YEAR ENDED           PERIOD ENDED
                                                                    DECEMBER 31, 1996    DECEMBER 31, 1995*
                                                                   -------------------   ------------------
<S>                                                                <C>                   <C>
Per share data (for a share outstanding throughout each period):
Net asset value--beginning of period.............................        $ 12.57               $10.00
                                                                         -------               ------
Income from investment operations#--
  Net investment incomeSection...................................        $  0.55               $ 0.39
  Net realized and unrealized gain on investments and foreign
    currency transactions........................................           1.78                 3.00
                                                                         -------               ------
    Total from investment operations.............................        $  2.33               $ 3.39
                                                                         -------               ------
Less distributions declared to shareholders--
  From net investment income.....................................        $ (0.35)              $(0.24)
  From net realized gain on investments and foreign currency
    transactions.................................................          (0.88)               (0.58)
  In excess of realized gain on investments and foreign currency
    transactions.................................................          (0.01)                  --
                                                                         -------               ------
    Total distributions declared to shareholders.................        $ (1.24)              $(0.82)
                                                                         -------               ------
Net asset value--end of period...................................        $ 13.66               $12.57
                                                                         -------               ------
                                                                         -------               ------
Total return.....................................................          18.51%               33.94%++
Ratios (to average net assets)/Supplemental dataSection:
  Expenses.......................................................           1.00%                1.00%+
  Net investment income..........................................           4.19%                3.66%+
Portfolio turnover...............................................            121%                  94%
Average commission rate###.......................................        $0.0416                   --
Net assets at end of period (000 omitted)........................        $ 9,572               $2,373
<FN>
- ------------------------
        *  For the period from the commencement of investment operations, January 3, 1995 to December 31, 1995.
        +  Annualized.
       ++  Not annualized.
        #  Per share data is based on average shares outstanding.
      ###  Average commission rate is calculated for funds with fiscal years beginning on or after September 1, 1995.
  Section  The  Adviser voluntarily agreed to maintain the  expenses of the Series at not  more than 1.00% of average daily
           net assets. To the extent actual expenses were over  these limitations, the net investment income per share  and
           the ratios would have been:
 
Net investment income............................................            $0.32             $0.17
Ratios (to average net assets):
  Expenses.......................................................             2.75%             3.08%+
  Net investment income..........................................             2.44%             1.62%+
</TABLE>
 
                                       8
<PAGE>
                            WORLD GOVERNMENTS SERIES
 
<TABLE>
<CAPTION>
                                                                       YEAR ENDED            YEAR ENDED          PERIOD ENDED
                                                                    DECEMBER 31, 1996    DECEMBER 31, 1995    DECEMBER 31, 1994*
                                                                   -------------------   ------------------   ------------------
<S>                                                                <C>                   <C>                  <C>
Per share data (for a share outstanding throughout each period):
Net asset value--beginning of period.............................        $ 10.17               $ 9.82               $10.00
                                                                         -------               ------               ------
Income from investment operations#--
  Net investment incomeSection...................................        $  0.60               $ 0.63               $ 0.17
  Net realized and unrealized gain (loss) on investments and
    foreign currency transactions................................          (0.19)                0.78                (0.09)
                                                                         -------               ------               ------
    Total from investment operations.............................        $  0.41               $ 1.41               $ 0.08
                                                                         -------               ------               ------
Less distributions declared to shareholders--
  From net investment income.....................................        $    --               $(0.42)              $(0.17)
  In excess of net investment income.............................             --                (0.54)               (0.09)
  Tax return of capital..........................................             --                (0.10)                  --
                                                                         -------               ------               ------
    Total distributions declared to shareholders.................        $    --               $(1.06)              $(0.26)
                                                                         -------               ------               ------
Net asset value--end of period...................................        $ 10.58               $10.17               $ 9.82
                                                                         -------               ------               ------
                                                                         -------               ------               ------
Total return.....................................................           4.03%               14.38%                0.79%++
Ratios (to average net assets)/Supplemental dataSection:
  Expenses.......................................................           1.00%                1.00%                1.00%+
  Net investment income..........................................           5.84%                6.05%                4.68%+
Portfolio turnover...............................................            361%                 211%                  62%
Net assets at end of period (000 omitted)........................        $26,023               $7,424               $2,881
</TABLE>
 
- ------------------------
 
<TABLE>
<C>        <S>
        *  For the period from the commencement of investment operations, June 14, 1994 to December 31, 1994.
        +  Annualized.
       ++  Not annualized.
        #  Per share data is based on average shares outstanding.
  Section  The  Adviser voluntarily agreed to maintain the expenses of the Series at not more than 1.00% of average daily net
           assets. To the extent actual  expenses were over these  limitations, the net investment  income per share and  the
           ratios would have been:
</TABLE>
 
<TABLE>
<S>                                                                <C>      <C>      <C>
Net investment income............................................  $0.50    $0.53    $0.16
Ratios (to average net assets):
  Expenses.......................................................   2.03%    1.99%    1.10%+
  Net investment income..........................................   4.81%    5.09%    4.58%+
</TABLE>
 
                                       9
<PAGE>
                                  BOND SERIES
 
<TABLE>
<CAPTION>
                                                                       YEAR ENDED          PERIOD ENDED
                                                                   DECEMBER 31, 1996    DECEMBER 31, 1995*
                                                                   ------------------   ------------------
<S>                                                                <C>                  <C>
Per share data (for a share outstanding throughout each period):
Net asset value--beginning of period.............................        $10.19               $10.00
                                                                         ------               ------
Income from investment operations#--
  Net investment incomeSection...................................        $ 0.58               $ 0.09
  Net realized and unrealized gain (loss) on investments.........         (0.36)                0.21
                                                                         ------               ------
    Total from investment operations.............................        $ 0.22               $ 0.30
                                                                         ------               ------
Less distributions declared to shareholders--
  From net investment income.....................................        $(0.35)              $(0.09)
  From net realized gain on investments..........................            --                (0.02)
                                                                         ------               ------
    Total distributions declared to shareholders.................        $(0.35)              $(0.11)
                                                                         ------               ------
Net asset value--end of period...................................        $10.06               $10.19
                                                                         ------               ------
                                                                         ------               ------
Total return.....................................................          2.09%                3.02%++
Ratios (to average net assets)/Supplemental dataSection:
  Expenses.......................................................          1.00%                1.00%+
  Net investment income..........................................          5.84%                4.89%+
Portfolio turnover...............................................           231%                  55%
Net assets at end of period (000 omitted)........................        $  853               $  228
<FN>
- ------------------------
        *  For the period from the commencement of investment operations, October 24, 1995 to December 31, 1995.
        +  Annualized.
       ++  Not annualized.
        #  Per share data is based on average shares outstanding.
  Section  The  Adviser voluntarily agreed to maintain the expenses of the  Series at not more than 1.00% of average daily net
           assets. To the extent actual expenses were over these limitations, the net investment loss per share and the ratios
           would have been:
 
Net investment loss..............................................        $ (0.26)            $ (0.70)
Ratios (to average net assets):
  Expenses.......................................................           9.45%              43.85%+
  Net investment loss............................................          (2.61)%            (37.96)%+
</TABLE>
 
                                       10
<PAGE>
4.  INVESTMENT OBJECTIVES AND POLICIES
 
    Each Series has  different investment  objectives which  it pursues  through
separate  investment policies, as described below. The differences in objectives
and policies among the Series can be expected to affect the degree of market and
financial risk to which each  Series is subject and  the return of each  Series.
The  investment objectives  and policies  of each  Series may,  unless otherwise
specifically stated, be changed by the Trustees  of the Trust without a vote  of
the  shareholders. Any investment  involves risk and there  is no assurance that
the objectives of any Series will be achieved.
 
    In addition  to  the specific  investment  practices described  below,  each
Series  may also engage in certain  investment techniques as described under the
caption  "Investment  Techniques"  below  and  in  the  SAI  under  the  caption
"Investment  Techniques." The Series' 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."
 
MFS EMERGING GROWTH SERIES  -- The Series seeks  to provide long-term growth  of
capital.  Dividend and  interest income  from portfolio  securities, if  any, is
incidental to the Series' investment objective of long-term growth of capital.
 
    The Series' policy is to invest primarily (I.E., at least 80% of its  assets
under  normal circumstances) in common stocks of companies that MFS believes are
early in  their  life  cycle  but  which have  the  potential  to  become  major
enterprises  (emerging  growth  companies). Such  companies  generally  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  can be  of any  size, and  the Series  may invest  in larger  or more
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 the economic environment.  While
the  Series will invest primarily in common stocks, the Series may, to a limited
extent, seek appreciation  in other  types of  securities such  as fixed  income
securities  (which  may be  unrated), convertible  securities and  warrants when
relative values  make  such purchases  appear  attractive either  as  individual
issues  or as types  of securities in certain  economic environments. The Series
may  invest  in  non-convertible  fixed  income  securities  rated  lower   than
"investment  grade"  (rated  Ba  or lower  by  Moody's  Investors  Service, Inc.
("Moody's") or BB  or lower  by Standard &  Poor's Ratings  Services ("S&P")  or
Fitch  Investors Service, Inc. ("Fitch")) (commonly known as "junk bonds") or in
comparable unrated securities,  when, in  the opinion  of the  Adviser, such  an
investment  presents a greater opportunity for appreciation with comparable risk
to  an  investment  in  "investment  grade"  securities.  Under  normal   market
conditions,  the Series will invest not more than  5% of its net assets in these
securities. For  a  description  of  these  ratings,  see  Appendix  A  to  this
Prospectus.
 
    The  nature of investing in emerging  growth companies involves greater risk
than is customarily associated with  investments in more established  companies.
Emerging growth companies often have limited product lines, markets or financial
resources,  and they  may be  dependent on  one-person management.  In addition,
there may be less  research available on many  promising small and medium  sized
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 larger, more established growth  companies or the market averages
in general. Shares of the Series, 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.
 
    Consistent with its investment objective  and policies described above,  the
Series  may also invest up to 25% (and generally expects to invest not more than
15%) of  its  net  assets  in  foreign  securities  (including  emerging  market
securities and Brady Bonds) which are not traded on a U.S. exchange.
 
MFS  RESEARCH SERIES -- The Research  Series' investment objective is to provide
long-term growth of capital and future income.
 
    The portfolio securities of the Research Series are selected by a  committee
of  investment research  analysts. This  committee includes  investment analysts
employed not only by the Adviser but also by MFS International (U.K.) Limited, a
wholly  owned  subsidiary  of  MFS.  The  Series'  assets  are  allocated  among
industries  by the analysts acting together  as a group. Individual analysts are
then responsible for selecting what they  view as the securities best suited  to
meet   the  Series'   investment  objective   within  their   assigned  industry
responsibility.
 
    The Research Series'  policy is to  invest a substantial  proportion of  its
assets in equity securities of companies believed to possess better than average
prospects for long-term growth. Equity securities in which the Series may invest
include the
 
                                       11
<PAGE>
following:  common stocks,  preferred stocks  and preference  stocks; securities
such as  bonds,  warrants  or  rights that  are  convertible  into  stocks;  and
depositary  receipts for  those securities.  These securities  may be  listed on
securities exchanges,  traded in  various over-the-counter  markets or  have  no
organized  markets. A smaller proportion of the assets may be invested in bonds,
short-term obligations,  preferred  stocks  or  common  stocks  whose  principal
characteristic is income production rather than growth. Such securities may also
offer opportunities for growth of capital as well as income. In the case of both
growth  stocks  and  income  issues,  emphasis is  placed  on  the  selection of
progressive,  well-managed   companies.   The   Series'   non-convertible   debt
investments,  if any, may consist of "investment grade" securities (rated Baa or
better by Moody's or BBB or better by S&P or by Fitch), and, with respect to  no
more  than  10%  of  the  Series' net  assets,  securities  in  the  lower rated
categories (rated Ba or lower by Moody's or  BB or lower by S&P or by Fitch)  or
securities  which the Adviser believes  to be of similar  quality to these lower
rated securities (commonly  known as "junk  bonds"). For a  description of  bond
ratings, see Appendix A to this Prospectus.
 
    Consistent  with its investment objective  and policies described above, the
Series may  also invest  up  to 20%  of its  net  assets in  foreign  securities
(including emerging market securities) which are not traded on a U.S. exchange.
 
MFS TOTAL RETURN SERIES -- The Total Return Series' primary investment objective
is to provide above-average income (compared to a portfolio invested entirely in
equity  securities) consistent with  the prudent employment  of capital, and its
secondary objective is to provide a reasonable opportunity for growth of capital
and income, since many securities offering a better than average yield may  also
possess  growth potential. Thus, in selecting  securities for its portfolio, the
Series considers each of  these objectives. Under  normal market conditions,  at
least 25% of the Total Return Series' assets will be invested in non-convertible
fixed  income securities, and at  least 40% and no more  than 75% of the Series'
assets will be  invested in equity  securities. Equity securities  in which  the
Series  may invest  include the following:  common stocks,  preferred stocks and
preference stocks;  securities  such  as  bonds, warrants  or  rights  that  are
convertible  into stocks;  and depositary  receipts for  those securities. These
securities  may  be   listed  on   securities  exchanges,   traded  in   various
over-the-counter markets or have no organized markets.
 
    The  Series' policy is  to invest in  a broad list  of securities, including
short-term obligations. The list  may be diversified not  only by companies  and
industries,  but also by type of security.  The Total Return Series may vary the
percentage of assets invested in any one type of security in accordance with the
Adviser's interpretation of  economic and  money market  conditions, fiscal  and
monetary  policy  and underlying  security  values. The  Series' non-convertible
fixed income  investments  may consist  of  both "investment  grade"  securities
(rated  Baa  or better  by Moody's  or BBB  or better  by S&P  or by  Fitch) and
securities that are unrated or are in  the lower rating categories (rated Ba  or
lower  by Moody's or  BB or lower by  S&P or by Fitch)  (commonly known as "junk
bonds") including  up to  20%  of its  assets  in non-convertible  fixed  income
securities  that are  in these  lower rating  categories and  comparable unrated
securities (see "Additional Risk Factors" below). Generally, most of the Series'
long-term non-convertible fixed income  investments will consist of  "investment
grade"  securities. See Appendix A to this Prospectus for a description of these
ratings.
 
    The  Series  may  also  invest  in  United  States  government   securities,
including:  (1) U.S. Treasury  obligations, which differ  only in their interest
rates, maturities and times of issuance: U.S. Treasury bills (maturities of  one
year  or less); U.S. Treasury  notes (maturities of one  to ten years); and U.S.
Treasury bonds (generally maturities  of greater than ten  years), all of  which
are  backed  by  the full  faith  and credit  of  the U.S.  Government;  and (2)
obligations issued or  guaranteed by  U.S. Government  agencies, authorities  or
instrumentalities,  some of which are backed by the full faith and credit of the
U.S. Treasury, E.G., direct pass-through certificates of the Government National
Mortgage Association ("GNMA"); some of which  are supported by the right of  the
issuer  to borrow  from the U.S.  Government, E.G., obligations  of Federal Home
Loan Banks;  and some  of which  are backed  only by  the credit  of the  issuer
itself,   E.G.,   obligations  of   the   Student  Loan   Marketing  Association
(collectively,  "U.S.  Government  Securities").   The  term  "U.S.   Government
Securities"  also includes  interests in  trusts or  other entities representing
interests in obligations that  are backed by  the full faith  and credit of  the
U.S.  Government  or  are  issued  or guaranteed  by  the  U.S.  Government, its
agencies, authorities or instrumentalities.
 
    Consistent with its investment objective  and policies described above,  the
Series  may  also invest  up  to 20%  of its  net  assets in  foreign securities
(including emerging market securities and Brady Bonds) which are not traded on a
U.S. exchange.
 
MFS UTILITIES SERIES --  The Utilities Series' investment  objective is to  seek
capital  growth and current income (income above that available from a portfolio
invested entirely in equity securities).
 
    The Utilities Series will seek to achieve its objective by investing,  under
normal  circumstances, at  least 65% (but  up to  100% at the  discretion of the
Adviser) of  its assets  in equity  and  debt securities  of both  domestic  and
foreign  companies in  the utilities  industry. Equity  securities in  which the
Series may  invest  include  the  following:  common  stocks;  preferred  stocks
 
                                       12
<PAGE>
and  preference stocks;  securities such as  bonds, warrants or  rights that are
convertible into stocks;  and depositary  receipts for  those securities.  These
securities   may  be   listed  on   securities  exchanges,   traded  in  various
over-the-counter markets  or have  no organized  markets. At  least 80%  of  the
non-convertible  fixed income securities held by the Series will be rated at the
time of investment at least Baa by Moody's or BBB by S&P or by Fitch or will  be
of  comparable  quality  as  determined by  the  Adviser  (see  "Additional Risk
Factors" below). See Appendix  A to this Prospectus  for a description of  these
ratings.  The Series may also invest in debt and equity securities of issuers in
other industries, as  discussed below, although  under normal circumstances  not
more than 35% of the Series' assets will be so invested. In addition, the Series
may hold a portion of its assets in cash and money market instruments.
 
    Companies  in the  utilities industry include  (i) companies  engaged in the
manufacture, production,  generation,  transmission,  sale  or  distribution  of
electric,  gas or other  types of energy,  water or other  sanitary services and
(ii) companies  engaged  in telecommunications,  including  telephone,  cellular
telephones,   telegraph,  satellite,  microwave,   cable  television  and  other
communications media (but  not companies  engaged in  public broadcasting).  The
Adviser  deems a particular company  to be in the  utilities industry if, at the
time of investment, the  Adviser determines that at  least 50% of the  company's
assets or revenues are derived from one or more of those industries. The portion
of  the Utilities Series' assets invested in a particular type of utility and in
equity or  debt securities  will vary  in light  of changes  in interest  rates,
market  conditions  and  economic  conditions  and  other  factors.  For further
information on the  principal sectors  of the  utilities industry  in which  the
Series may invest, see Appendix B to this Prospectus.
 
    Consistent  with its investment objective  and policies described above, the
Series may  also invest  up  to 35%  of its  net  assets in  foreign  securities
(including emerging market securities and Brady Bonds) which are not traded on a
U.S. exchange.
 
    Since   the  Utilities  Series'  investments  are  concentrated  in  utility
securities, the  value of  the Series'  shares will  be especially  affected  by
factors  peculiar to the utilities industry,  and may fluctuate more widely than
the value of shares of a fund that invests in a broader range of industries. The
rates many  utility  companies may  charge  their customers  are  controlled  by
governmental  regulatory commissions which may result  in a delay in the utility
company passing along increases in costs to its customers. Furthermore, there is
no assurance  that  regulatory  authorities  will, in  the  future,  grant  rate
increases  or that  such increases  will be  adequate to  permit the  payment of
dividends on common stocks. Many utility companies, especially electric and  gas
and   other   energy  related   utility  companies,   are  subject   to  various
uncertainties, including: risks of increases in fuel and other operating  costs;
the  high cost of borrowing to  finance capital construction during inflationary
periods; difficulty  obtaining adequate  returns on  invested capital,  even  if
frequent rate increases are approved by public service commissions; restrictions
on  operations and increased costs  and delays as a  result of environmental and
nuclear safety regulations; securing  financing for large construction  projects
during  an inflationary period; difficulties of the capital markets in absorbing
utility debt and equity  securities; difficulty in  raising capital in  adequate
amounts  on reasonable terms in periods  of high inflation and unsettled capital
markets; technological innovations which  may render existing plants,  equipment
or  products obsolete;  the potential impact  of natural  or man-made disasters;
difficulties in obtaining natural gas for resale or fuel for electric generation
at reasonable prices; coping  with the general  effects of energy  conservation,
particularly  in light of changing policies  regarding energy; and special risks
associated with  the  construction and  operation  of nuclear  power  generating
facilities,  including  technical factors  and costs,  and the  possibility that
federal, state and municipal government authorities may from time to time review
existing  requirements  and  impose  additional  requirements.  Certain  utility
companies,  especially gas and telephone utility companies, have in recent years
been affected  by  increased  competition,  which  could  adversely  affect  the
profitability  of such  utility companies. Furthermore,  there are uncertainties
resulting from certain  telecommunications companies'  diversification into  new
domestic  and  international  businesses  as well  as  agreements  by  many such
companies linking  future  rate increases  to  inflation or  other  factors  not
directly related to the active operating profits of the enterprise.
 
    Foreign  utility  companies are  also subject  to regulation,  although such
regulations may or may not be comparable to those in the United States.  Foreign
utility  companies may be more heavily regulated by their respective governments
than utilities in the U.S. and, as  in the U.S., generally are required to  seek
government  approval  for  rate  increases.  In  addition,  since  many  foreign
utilities use fuel that causes more pollution than those used in the U.S.,  such
utilities  may be required to invest in  pollution control equipment to meet any
proposed pollution restrictions. Foreign regulatory systems vary from country to
country and may evolve in ways different from regulation in the U.S.
 
    The Utilities Series is  permitted to invest in  securities of issuers  that
are outside the utilities industry, although under normal circumstances not more
than 35% of the Series' assets will be so invested. Such investments may include
common  stocks,  debt  securities  (including  municipal  debt  securities)  and
preferred   stocks    and   will    be   selected    to   meet    the    Series'
 
                                       13
<PAGE>
investment objective of both capital growth and current income. These securities
may be issued by either U.S. or non-U.S. companies. Some of these issuers may be
in  industries related to the utilities  industry and, therefore, may be subject
to similar risks.
 
    Investments outside the utilities industry may also include U.S.  Government
Securities,   as  that  term   is  defined  under   "Investment  Objectives  and
Policies--MFS Total Return Series" above. When and if available, U.S. Government
Securities may be purchased at a  discount from face value. However, the  Series
does not intend to hold such securities to maturity for the purpose of achieving
potential  capital  gains,  unless  current  yields  on  the  securities  remain
attractive.
 
MFS WORLD  GOVERNMENTS  SERIES  --  The  World  Governments  Series'  investment
objective  is to seek not only preservation but also growth of capital, together
with moderate current income.
 
    The World  Governments  Series seeks  to  achieve its  investment  objective
through   a  professionally   managed,  internationally   diversified  portfolio
consisting  primarily  of  debt  securities  and  to  a  lesser  extent   equity
securities.  The Series  attempts to  provide investors  with an  opportunity to
enhance the  value  and increase  the  protection of  their  investment  against
inflation  and otherwise by taking advantage  of investment opportunities in the
U.S. as well as in other countries where opportunities may be more rewarding. It
is believed that diversification of  assets on an international basis  decreases
the  degree to which events  in any one country,  including the U.S., can affect
the entire portfolio. Although the percentage of the Series' assets invested  in
securities  issued  abroad  and  denominated  in  foreign  currencies  will vary
depending on the state of the economies of the principal countries of the world,
their financial markets  and the relationship  of their currencies  to the  U.S.
dollar,  under  normal  conditions  the  Series'  portfolio  is  internationally
diversified. However,  for  temporary  defensive  reasons  or  during  times  of
international  political or economic uncertainty or  turmoil, most or all of the
Series' investments may be in the U.S.
 
    Under normal economic  and market conditions,  at least 80%  of the  Series'
portfolio  is invested in  debt securities, such  as bonds, debentures, mortgage
securities, notes,  commercial  paper, obligations  issued  or guaranteed  by  a
government  or any of its political subdivisions, agencies or instrumentalities,
certificates of deposit, as well  as debt obligations which  may have a call  on
common stock by means of a conversion privilege or attached warrants.
 
    Consistent  with its investment objective  and policies described above, the
Series may invest up to 100% (and generally expects to invest not more than 80%)
of its net assets  in foreign securities  (including emerging market  securities
and  Brady  Bonds)  which  are  not traded  on  a  U.S.  exchange.  Although the
percentage of the Series'  assets invested in foreign  securities will vary,  at
least  65% of the  Series' assets will  be invested in  at least three different
countries, one of which may be the  U.S., except when the Adviser believes  that
investing  for  temporary defensive  purposes is  appropriate. The  Adviser will
determine the amount of the World  Governments Series' assets to be invested  in
the  U.S. and the amount to be invested abroad. The U.S. assets will be invested
in high  quality  debt  securities and  the  remainder  of the  assets  will  be
diversified among countries where opportunities for total return are expected to
be  most attractive.  It is currently  expected that  investments within foreign
countries will be primarily in  government securities to minimize credit  risks.
The  Series  will not  invest 25%  or more  of the  value of  its assets  in the
securities of any one foreign government. The portfolio will be managed actively
and the asset allocations modified as the Adviser deems necessary.
 
    The World Governments Series will purchase non-dollar securities denominated
in the currency of countries where the interest rate environment as well as  the
general economic climate provide an opportunity for declining interest rates and
currency  appreciation. If  interest rates  decline, such  non-dollar securities
will appreciate in value. If the  currency also appreciates against the  dollar,
the  total investment in  such non-dollar securities  would be enhanced further.
Conversely, a rise in interest rates or decline in currency exchange rates would
adversely affect  the  Series'  return. Investments  in  non-dollar  denominated
securities  are evaluated  primarily on  the strength  of a  particular currency
against the dollar and on the interest rate climate of that country. Currency is
judged on the basis of  fundamental economic criteria (E.G., relative  inflation
levels  and  trends,  growth rate  forecasts,  balance of  payments  status, and
economic policies) as well as technical  and political data. In addition to  the
foregoing,  interest  rates  are  evaluated on  the  basis  of  differentials or
anomalies that  may  exist between  different  countries. The  Series  may  hold
foreign  currency received in connection  with investments in foreign securities
and in  anticipation of  purchasing foreign  securities. (See  "Additional  Risk
Factors" below.)
 
    The  phrase "preservation of capital" when  applied to a domestic investment
company is generally understood to imply that the portfolio is invested in  very
low  risk securities and that the major risk is loss of purchasing power through
the effects of inflation or major changes in interest rates. However, while  the
World  Governments  Series  invests in  securities  which are  believed  to have
minimal credit risk, an error of judgment in selecting a currency or an interest
rate environment could result in a loss of capital.
 
                                       14
<PAGE>
    It  is  contemplated  that  the  World  Governments  Series'  long-term debt
investments will  consist primarily  of  securities which  are believed  by  the
Adviser  to be of relatively high quality.  If after the Series purchases such a
security, the quality of the  security deteriorates significantly, the  security
will be sold only if the Adviser believes it is advantageous to do so.
 
MFS  BOND SERIES -- The Bond Series'  primary investment objective is to provide
as high a level of current income  as is believed to be consistent with  prudent
investment  risk. The  Series' secondary  objective is  to protect shareholders'
capital.
 
    The Series seeks  to achieve  its investment objective  by investing,  under
normal market conditions, at least 65% of its total assets in:
 
    (1) convertible and non-convertible debt securities and preferred stocks;
 
    (2)  U.S. Government  Securities, as  defined in  "Investment Objectives and
       Policies--MFS Total Return Series" above; and
 
    (3) commercial paper,  repurchase agreements  and cash  or cash  equivalents
       (such as certificates of deposit and bankers' acceptances).
 
    Not  more than 20% of the Series' net assets will be invested in convertible
and non-convertible securities rated below the four highest grades of S&P, Fitch
(AAA, AA,  A or  BBB) or  Moody's (Aaa,  Aa, A  or Baa)  and comparable  unrated
securities. For a description of these ratings see Appendix A to this Prospectus
and  Appendix  C  for a  chart  showing  the Series'  holdings  of  fixed income
securities broken down  by rating  category as  of the  end of  its most  recent
fiscal  year. For a discussion of the risks of investing in these securities see
"Additional Risk Factors" below.
 
    Although the Bond Series may purchase Canadian and other foreign securities,
under normal market conditions, it may not invest more than 10% of its assets in
non-dollar  denominated  non-Canadian  foreign  securities,  including  emerging
market securities and Brady Bonds. The Series may hold foreign currency received
in  connection  with investments  in foreign  securities  or in  anticipation of
purchasing foreign securities. (See "Investment Techniques" and "Additional Risk
Factors" below.)
 
    The Bond Series may not directly purchase common stocks. However, the Series
may retain up to 10%  of its total assets in  common stocks which were  acquired
either  by conversion of fixed income securities  or by the exercise of warrants
attached thereto.
 
5.  INVESTMENT TECHNIQUES
 
    LENDING OF PORTFOLIO SECURITIES: Each Series may seek to increase its income
by lending portfolio securities. Such loans will usually be made 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.  Treasury 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. If the Adviser determines to
make  securities loans, it is  intended that the value  of the securities loaned
would not exceed 10%  of the value of  the net assets of  the Series making  the
loans.
 
    EMERGING  MARKET  SECURITIES: Consistent  with their  respective objectives,
each Series 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  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 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: Each Series  (except the Research Series)  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
 
                                       15
<PAGE>
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, Dominican  Republic, Ecuador, Jordan,
Mexico, Nigeria, Panama, the Philippines,  Poland, 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.
 
    REPURCHASE  AGREEMENTS: Each Series may  enter into repurchase agreements in
order to earn  income on  available cash or  as a  temporary defensive  measure.
Under  a  repurchase  agreement, a  Series  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 Series' right to liquidate the securities
may be restricted (during which time the value of the securities could decline).
As discussed in the SAI, each Series has adopted certain procedures intended  to
minimize risk.
 
    "WHEN-ISSUED"  SECURITIES: Each Series  (except the Research  Series and the
World Governments Series)  may purchase securities  on a "when-issued"  or on  a
"forward  delivery" basis, which means that  the securities will be delivered to
the Series  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. In general, a  Series does not pay  for
such  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,  a Series  will normally  invest in liquid
assets.
 
    MORTGAGE "DOLLAR ROLL" TRANSACTIONS: Each Series (except the Emerging Growth
Series  and  the  Research  Series)  may  enter  into  mortgage  "dollar   roll"
transactions  with selected banks and broker-dealers  pursuant to which a Series
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 Series
record these  transactions as  sale and  purchase transactions,  rather than  as
borrowing  transactions. A Series 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.  In the event that  the
party with whom the Series contracts to replace substantially similar securities
on a future date fails to deliver such securities, the Series may not be able to
obtain  such securities at the price specified in such contract and thus may not
benefit from the  price differential  between the  current sales  price and  the
repurchase price.
 
    RESTRICTED  SECURITIES:  Each Series  may purchase  securities that  are not
registered under  the  Securities Act  of  1933 (the  "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 Series' limitation 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 determining and monitoring the liquidity
of Rule  144A securities.  The Board,  however, retains  oversight, 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 a Series to the  extent that qualified institutional buyers become
for a time uninterested in purchasing  Rule 144A securities held in the  Series'
portfolio.
 
    CORPORATE  ASSET-BACKED SECURITIES: Each Series  (except the Research Series
and  the  World  Governments  Series)  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
 
                                       16
<PAGE>
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. The  underlying
assets  (E.G.,  loans)  are  also  subject  to  prepayments  which  shorten  the
securities' weighted average life and may lower their return.
 
    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  on underlying  assets  to make  payments,  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. A Series
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.
 
    ZERO  COUPON  BONDS,  DEFERRED INTEREST  BONDS  AND PIK  BONDS:  Each Series
(except the Emerging Growth Series and  the Research Series) may invest in  zero
coupon  bonds. The Total  Return Series and  the Bond Series  may also invest in
deferred interest bonds and 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. Each  Series 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 Series' distribution obligations.
 
    COLLATERALIZED  MORTGAGE OBLIGATIONS AND MULTICLASS PASS-THROUGH SECURITIES:
Each of the Bond Series, the  World Governments Series and the Utilities  Series
may  invest a  portion of its  assets in collateralized  mortgage obligations or
"CMOs," which are debt obligations collateralized by mortgage loans or  mortgage
pass-through  securities.  Typically,  CMOs are  collateralized  by certificates
issued by  GNMA,  the Federal  National  Mortgage Association  ("FNMA")  or  the
Federal Home Loan Mortgage Corporation ("FHLMC"), but also may be collateralized
by  whole  loans or  private mortgage  pass-through securities  (such collateral
collectively referred to as  "Mortgage Assets"). Each of  these Series may  also
invest  a portion of its assets  in multiclass pass-through securities which are
interests in a trust composed of Mortgage Assets. CMOs (which include multiclass
pass-through  securities)   may   be   issued  by   agencies,   authorities   or
instrumentalities  of  the  U.S. Government  or  by private  originators  of, or
investors in, mortgage loans, including savings and loan associations,  mortgage
banks,  commercial banks, investment  banks and special  purpose subsidiaries of
the foregoing. Payments of principal of and interest on the Mortgage Assets, and
any reinvestment income thereon,  provide the funds to  pay debt service on  the
CMOs  or make scheduled distributions on the multiclass pass-through securities.
In a CMO,  a series  of bonds  or certificates  are usually  issued in  multiple
classes  with different maturities. Each  class of CMOs, often  referred to as a
"tranche," is issued  at a  specific fixed  or floating  coupon rate  and has  a
stated  maturity  or  final  distribution  date.  Principal  prepayments  on the
Mortgage Assets may  cause the  CMOs to  be retired  substantially earlier  than
their  stated maturities or final distribution dates, resulting in a loss of all
or part  of the  premium if  any has  been paid.  Certain classes  of CMOs  have
 
                                       17
<PAGE>
priority  over  others  with  respect  to  the  receipt  of  prepayments  on the
mortgages. Therefore, depending on the type  of CMOs in which a Series  invests,
the  investment may be subject  to a greater or  lesser risk of prepayments than
other types of mortgage-related securities.
 
    Each of  these Series  may also  invest  in parallel  pay CMOs  and  Planned
Amortization  Class  CMOs ("PAC  Bonds"). Parallel  pay  CMOs are  structured to
provide payments of principal on each payment  date to more than one class.  PAC
Bonds  generally require  payments of  a specified  amount of  principal on each
payment date. PAC Bonds are always parallel pay CMOs with the required principal
payment on such securities having the  highest priority after interest has  been
paid  to all classes. For  a further description of  CMOs, parallel pay CMOs and
PAC Bonds and the risks related to transactions therein, see the SAI.
 
    STRIPPED MORTGAGE-BACKED SECURITIES: Each of  the Bond Series and the  World
Governments   Series  may   invest  a   portion  of   its  assets   in  stripped
mortgage-backed securities ("SMBS"),  which are  derivative multiclass  mortgage
securities   usually  structured   with  two  classes   that  receive  different
proportions of interest and principal  distributions from an underlying pool  of
mortgage  assets. For  a further  description of SMBS  and the  risks related to
transactions therein, see the SAI.
 
    LOAN PARTICIPATIONS  AND OTHER  DIRECT INDEBTEDNESS:  Each of  the  Emerging
Growth  Series and the Total Return Series may invest a portion of its assets in
"loan participations"  and  other  direct indebtedness.  By  purchasing  a  loan
participation,  a Series acquires some or all of the interest of a bank or other
lending institution  in a  loan to  a corporate  borrower. Many  such loans  are
secured,  and  most  impose  restrictive  covenants which  must  be  met  by the
borrower. These loans are  made generally to  finance internal growth,  mergers,
acquisitions,   stock  repurchases,  leveraged   buy-outs  and  other  corporate
activities. Such loans may be in default  at the time of purchase. A Series  may
also  purchase other direct  indebtedness such as trade  or other claims against
companies, which generally represent money owed by the company to a supplier  of
goods  and  services. These  claims may  also be  purchased at  a time  when the
company is  in default.  Certain of  the loan  participations and  other  direct
indebtedness  acquired by  a Series may  involve revolving  credit facilities or
other standby financing commitments  which obligate a  Series to pay  additional
cash on a certain date or on demand.
 
    The highly leveraged nature of many such loans and other direct indebtedness
may  make such  loans especially  vulnerable to  adverse changes  in economic or
market conditions. Loan participations and other direct indebtedness may not  be
in  the form of  securities or may  be subject to  restrictions on transfer, and
only limited opportunities may exist to resell such instruments. As a result,  a
Series  may be unable to sell such investments  at an opportune time or may have
to resell them at less than fair market value. For a further discussion of  loan
participations,  other direct indebtedness and the risks related to transactions
therein, see the SAI.
 
    MORTGAGE PASS-THROUGH SECURITIES: Each of the Total Return Series, the  Bond
Series  and the  World Governments  Series may  invest in  mortgage pass-through
securities.  Mortgage  pass-through   securities  are  securities   representing
interests  in  "pools" of  mortgage loans.  The Utilities  Series may  invest in
mortgage pass-through securities that are securities issued or guaranteed as  to
principal  and interest  by the  U.S. Government,  its agencies,  authorities or
instrumentalities. Monthly payments of interest and principal by the  individual
borrowers  on mortgages are passed through to the holders of the securities (net
of fees paid to the issuer or  guarantor of the securities) as the mortgages  in
the underlying mortgage pools are paid off. Payment of principal and interest on
some  mortgage  pass-through  securities  (but  not  the  market  value  of  the
securities themselves) may  be guaranteed by  the full faith  and credit of  the
U.S. Government (in the case of securities guaranteed by GNMA); or guaranteed by
U.S.  Government-sponsored  corporations  (such  as  FNMA  or  FHLMC,  which are
supported only by the discretionary authority of the U.S. Government to purchase
the agency's obligations). Mortgage pass-through  securities may also be  issued
by  non-governmental  issuers  (such  as  commercial  banks,  savings  and  loan
institutions, private mortgage insurance  companies, mortgage bankers and  other
secondary  market  issuers).  See the  SAI  for  a further  discussion  of these
securities.
 
    INDEXED SECURITIES: Each of  the Total Return Series,  the Bond Series,  the
Utilities  Series  and  the  World  Governments  Series  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)  and/or interest  rates rise  or fall  according to the
change in one or more  specified underlying instruments. Indexed securities  may
be  positively or  negatively indexed (I.E.,  their principal  value or interest
rates may
 
                                       18
<PAGE>
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.
 
    SWAPS AND  RELATED TRANSACTIONS:  As one  way of  managing its  exposure  to
different  types of  investments, each of  the World Governments  Series and the
Bond Series may enter into interest  rate swaps, currency swaps and other  types
of  available swap agreements,  such as caps, collars  and floors. Swaps involve
the exchange  by  a  Series with  another  party  of cash  payments  based  upon
different  interest rate indexes, currencies, and other prices or rates, such as
the value of  mortgage prepayment rates.  For example, in  the typical  interest
rate  swap,  a Series  might exchange  a sequence  of cash  payments based  on a
floating rate index for cash  payments based on a  fixed rate. Payments made  by
both parties to a swap transaction are based on a principal amount determined by
the parties.
 
    The  World Governments Series and the Bond Series may also purchase and sell
caps, floors and collars. In a typical cap or floor agreement, one party  agrees
to  make  payments only  under specified  circumstances,  usually in  return for
payment of a fee by the counterparty.  For example, the purchase of an  interest
rate  cap entitles  the buyer, to  the extent  that a specified  index exceeds a
predetermined  interest   rate,   to  receive   payments   of  interest   on   a
contractually-based principal amount from the counterparty selling such interest
rate  cap.  The sale  of an  interest rate  floor obligates  the seller  to make
payments to the extent that a specified interest rate falls below an agreed-upon
level. A collar  arrangement combines  elements of buying  a cap  and selling  a
floor.
 
    Swap  agreements will tend  to shift a Series'  investment exposure from one
type of  investment to  another. For  example, if  a Series  agreed to  exchange
payments  in dollars for payments  in foreign currency, in  each case based on a
fixed rate, the swap agreement would tend to decrease a Series' exposure to U.S.
interest rates and increase its exposure to foreign currency and interest rates.
Caps and floors have an effect  similar to buying or writing options.  Depending
on  how they  are used,  swap agreements  may increase  or decrease  the overall
volatility of a Series' investments and its share price and yield.
 
    Swap agreements are sophisticated hedging instruments that typically involve
a small investment  of cash relative  to the  magnitude of risks  assumed. As  a
result,  swaps can be  highly volatile and  may have a  considerable impact on a
Series' performance.  Swap  agreements  are  subject to  risks  related  to  the
counterparty's   ability  to   perform,  and  may   decline  in   value  if  the
counterparty's creditworthiness deteriorates. A Series may also suffer losses if
it is unable  to terminate outstanding  swap agreements or  reduce its  exposure
through offsetting transactions.
 
    Swaps,  caps,  floors and  collars are  highly specialized  activities which
involve certain risks.  See the SAI  for further information  on, and the  risks
involved in, these activities.
 
    OPTIONS  ON  SECURITIES: Each  Series (except  the  Research Series  and the
Utilities Series) may write (sell) covered put and call options and purchase put
and call  options on  securities. Each  of these  Series will  write options  on
securities  for the purpose of increasing its return and/or to protect the value
of its portfolio. In  particular, where a Series  writes an option that  expires
unexercised  or is  closed out  by the Series  at a  profit, it  will retain the
premium paid for the option which will increase its gross income and will offset
in part the reduced  value of the portfolio  security underlying the option,  or
the increased cost of portfolio securities to be acquired. In contrast, however,
if the price of the underlying security moves adversely to the Series' position,
the  option may be exercised and the Series will be required to purchase or sell
the underlying security at a disadvantageous price, which may only be  partially
offset  by the amount of the premium.  The Series 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.
 
    By writing a call option on a  security, a Series limits its opportunity  to
profit  from any increase in the market  value of the underlying security, since
the holder will usually exercise  the call option when  the market value of  the
underlying  security exceeds the exercise price of the call. However, the Series
retains the risk of depreciation in value of securities on which it has  written
call options.
 
    Each  of these Series may also purchase  put or call options in anticipation
of market fluctuations which may adversely affect the value of its portfolio  or
the prices of securities that a Series wants to purchase at a later date. In the
event  that the expected  market fluctuations occur,  the Series may  be able to
offset  the  resulting  adverse  effect  on  its  portfolio,  in  whole  or   in
 
                                       19
<PAGE>
part,  through the options purchased. The premium  paid for a put or call option
plus any transaction  costs will  reduce the benefit,  if any,  realized by  the
Series  upon exercise or liquidation of the option, and, unless the price of the
underlying security changes sufficiently, the option may expire without value to
the Series.
 
    In certain instances the  Emerging Growth Series may  enter into options  on
Treasury  securities that  are "reset"  options or  "adjustable strike" options.
These options provide for periodic adjustment  of the strike price and may  also
provide  for  the periodic  adjustment of  the  premium during  the term  of the
option. The SAI contains a further discussion of these investments.
 
    OPTIONS ON STOCK  INDICES: Each  of the  Emerging Growth  Series, the  Total
Return  Series and the  Utilities Series may  write (sell) covered  call and put
options and purchase call and put options on stock indices. Each of these Series
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 a  Series
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 Series will
either close out the  option at a  profit or allow it  to expire unexercised.  A
Series  will thereby retain the amount  of the premium, less related transaction
costs, 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  a Series for  the writing of  the option, less related
transaction costs.  In addition,  if  the value  of  an underlying  index  moves
adversely  to a Series'  option position, the  option may be  exercised, and the
Series will experience a loss which may  only be partially offset by the  amount
of the premium received.
 
    Each  of these Series 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. A
Series' possible loss in either case will be limited to the premium paid for the
option, plus related transaction costs.
 
    "YIELD  CURVE" OPTIONS: Each of the Total Return Series, the Bond Series and
the World Governments Series  may enter into options  on the yield "spread,"  or
yield  differential,  between two  securities, a  transaction  referred to  as a
"yield curve" option, for hedging and non-hedging (an effort to increase current
income) purposes. 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  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 a  Series 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
"Additional 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.
 
    FUTURES CONTRACTS AND OPTIONS ON FUTURES CONTRACTS: Each of the Total Return
Series,  the Bond Series, the World  Governments Series and the Utilities Series
may purchase and  sell futures  contracts on  foreign or  domestic fixed  income
securities  or indices of such securities,  including municipal bond indices and
any other indices of foreign or domestic fixed income securities that may become
available for  trading ("Futures  Contracts").  Each of  these Series  may  also
purchase  and  write  options on  such  Futures Contracts  ("Options  on Futures
Contracts"). Each of the Emerging Growth Series and the Total Return Series  may
purchase  and sell Futures Contracts on stock indices, while the Emerging Growth
Series, the Total Return Series, the World Governments Series and the  Utilities
Series  may purchase and sell Futures Contracts on foreign currencies or indices
of foreign currencies. Each of these Series may also purchase and write  Options
on such Futures Contracts.
 
    Such  transactions  will  be  entered  into  for  hedging  purposes  or  for
non-hedging purposes to the extent permitted by applicable law. Each Series 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  a
Series, if its investment judgment about the general direction of exchange rates
or  the stock market is incorrect, the Series' overall performance may be poorer
than if it had not entered into any  such contract and the Series may realize  a
loss.  A  Series  will  not  enter  into  any  Futures  Contract  if immediately
thereafter the value  of securities  and other obligations  underlying all  such
Futures Contracts held by such Series would exceed 50% of the value of its total
assets.
 
    Purchases of Options on Futures Contracts may present less risk in hedging a
Series'  portfolio than the purchase or sale of the underlying Futures Contracts
since the potential loss is  limited to the amount  of the premium plus  related
transaction
 
                                       20
<PAGE>
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, a Series
may suffer a loss on the transaction.
 
    Futures  Contracts and Options on Futures Contracts that are entered into by
a Series will be traded on U.S. and foreign exchanges.
 
    FORWARD CONTRACTS:  Each  Series 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"). Each of these Series may  enter
into Forward Contracts for hedging purposes and (except for the Bond Series) for
non-hedging purposes (I.E., speculative purposes). By entering into transactions
in  Forward Contracts for hedging  purposes, a Series 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,  a Series 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. A Series may choose to, or be required
to,  receive delivery of the foreign  currencies underlying Forward Contracts 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 Series  may hold  such currencies  for an
indefinite period of time. A  Series 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.  Each of  these  Series  has
established  procedures  consistent with  statements of  the  SEC and  its staff
regarding the use of Forward Contracts by registered investment companies, which
requires use of segregated assets or "cover" in connection with the purchase and
sale of such contracts.
 
    OPTIONS ON FOREIGN CURRENCIES: Each Series (except the Research Series)  may
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 a Series 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 a Series' position, it may  forfeit the entire amount of the  premium
paid for the option plus related transaction costs. A Series 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, a Series may hold such  currencies
for an indefinite period of time.
 
6.  ADDITIONAL RISK FACTORS
 
    OPTIONS,  FUTURES CONTRACTS  AND FORWARD CONTRACTS:  Although certain Series
will enter into transactions in  options, Futures Contracts, Options on  Futures
Contracts,  Forward  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  or Futures
Contract and the  assets being  hedged, or unexpected  adverse price  movements,
could render a Series' hedging strategy unsuccessful and could result in losses.
Certain  Series also may enter into  transactions in options, Futures Contracts,
Options on  Futures  Contracts and  Forward  Contracts for  other  than  hedging
purposes,  which  involves greater  risk. In  particular, such  transactions may
result in losses for a Series 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  a
Series  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.
 
                                       21
<PAGE>
    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 and  indexes
underlying options, Futures Contracts and Options on Futures Contracts traded by
the Series will include both domestic and foreign securities.
 
    LOWER  RATED BONDS:  Each Series (except  the World  Governments Series) may
invest in fixed income securities  rated Baa by Moody's or  BBB by S&P 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 securities.
 
    Each of these  Series may also  invest in  securities rated Ba  or lower  by
Moody's  or  BB or  lower  by S&P  or  Fitch and  comparable  unrated securities
(commonly known as "junk bonds") to  the extent described above. See Appendix  A
to  this Prospectus  for a  description of  these ratings.  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 rating
categories. However, since 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 short-term corporate and industry
developments 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, the market's  perception of  their credit  quality, and  the outlook  for
economic  growth). 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. During certain periods, the higher yields on a
Series'  lower rated  high yielding fixed  income securities  are paid primarily
because of the increased risk of loss of principal and income, arising from such
factors as the heightened possibility of default or bankruptcy of the issuers of
such securities. Due to the fixed income payments of these securities, a  Series
may continue to earn the same level of interest income while its net asset value
declines  due to  portfolio losses,  which could  result in  an increase  in the
Series' yield despite the actual loss  of principal. The market for these  lower
rated  fixed income securities may be less liquid than the market for investment
grade fixed income securities, and judgment may at times play a greater role  in
valuing  these  securities than  in the  case of  investment grade  fixed income
securities. Changes in the value  of securities subsequent to their  acquisition
will  not  affect cash  income or  yield to  maturity  to a  Series but  will be
reflected in the net asset value of shares  of the Series. See the SAI for  more
information on lower rated securities.
 
    FOREIGN  SECURITIES:  Each  Series  may  invest  in  dollar-denominated  and
non-dollar-denominated 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 U.S. 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. Each  Series 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. Such Series 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.
 
    AMERICAN  DEPOSITARY RECEIPTS: Each  of the Series may  invest in 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 U.S. 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.
 
                                       22
<PAGE>
    EMERGING  MARKET  SECURITIES:  Each of  the  Series may  invest  in emerging
markets. In addition to  the general risks of  investing in foreign  securities,
investments  in  emerging  markets  involve special  risks.  Securities  of many
issuers in emerging markets may be less liquid and more volatile than securities
of comparable domestic issuers. These  securities may be considered  speculative
and,  while  generally  offering higher  income  and the  potential  for capital
appreciation, may present significantly greater risk. Emerging markets may  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 a Series is uninvested and no return is earned thereon. The  inability
of a Series to make intended security purchases due to settlement problems could
cause a Series to miss attractive investment opportunities. Inability to dispose
of  portfolio securities due to settlement problems  could result in losses to a
Series due  to subsequent  declines  in value  of  the portfolio  securities,  a
decrease  in the level of  liquidity in a Series' portfolio,  or if a Series has
entered into  a  contract  to  sell the  security,  possible  liability  to  the
purchaser.  Certain markets may require  payment for securities before delivery,
and in such  markets a Series  bears the risk  that the securities  will not  be
delivered  and that the Series' 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 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 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. A Series 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 Series 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 a Series.
 
    NON-DIVERSIFICATION: Each of the World Governments Series and the  Utilities
Series  is "non-diversified," as that term  is defined in the Investment Company
Act of 1940 ( the "1940 Act"), but intends to qualify as a "regulated investment
company" ("RIC") for federal income tax  purposes. This means, in general,  that
although  more  than 5%  of  the Series'  total assets  may  be invested  in the
securities of one issuer (including a foreign government), at the close of  each
quarter of its taxable year the aggregate amount of such holdings may not exceed
50%  of the value of its total assets, and  no more than 25% of the value of its
total assets may be invested in the securities of a single issuer. To the extent
that a non-diversified  Series at  times may hold  the securities  of a  smaller
number  of issuers than if  it were "diversified" (as  defined in the 1940 Act),
the Series will at  such times be  subject to greater risk  with respect to  its
portfolio  securities than a fund that invests in a broader range of securities,
because changes in  the financial  condition or  market assessment  of a  single
issuer  may cause greater fluctuations  in the Series' total  return and the net
asset value of its shares.
                              -------------------
 
SHORT-TERM INVESTMENTS FOR  TEMPORARY DEFENSIVE  PURPOSES --  During periods  of
unusual market conditions when the Adviser believes that investing for temporary
defensive  purposes is appropriate,  or in order  to meet anticipated redemption
requests, a large portion or all of the assets of each Series may be invested in
cash (including foreign currency) or cash equivalents including, but not limited
to,  obligations  of   banks  (including  certificates   of  deposit,   bankers'
acceptances,   time  deposits  and  repurchase  agreements),  commercial  paper,
short-term notes, U.S. Government Securities and related repurchase agreements.
 
                                       23
<PAGE>
PORTFOLIO TRADING
 
    Each  Series  intends  to  manage  its  portfolio  by  buying  and   selling
securities,  as  well as  holding  securities to  maturity,  to help  attain its
investment objectives and policies.
 
    Each Series will engage in portfolio  trading if it believes a  transaction,
net  of  costs  (including  custodian  charges),  will  help  in  attaining  its
investment objectives. In trading portfolio  securities, a Series 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 Series in trading portfolio securities, see "Portfolio Transactions
and Brokerage Commissions" in the SAI.  The Total Return Series' portfolio  will
be  managed actively with respect to the Series' fixed income securities and the
asset allocations modified as the  Adviser deems necessary. Although the  Series
does  not  intend to  seek short-term  profits, fixed  income securities  in its
portfolio will be sold whenever the Adviser believes it is appropriate to do  so
without  regard to the length  of time the particular  asset may have been held.
With respect to its equity securities,  the Total Return Series does not  intend
to  trade in  securities for short-term  profits and  anticipates that portfolio
securities ordinarily will be held for  one year or longer. However, the  Series
will effect trades whenever it believes that changes in its portfolio securities
are appropriate.
 
    Because  each of the Utilities Series,  the World Governments Series and the
Bond Series  is  expected  to have  a  portfolio  turnover rate  of  over  100%,
transaction  costs incurred  by the  Series and  the realized  capital gains and
losses of the Series may be greater than that of a fund with a lesser  portfolio
turnover rate.
 
    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 Rules of Fair
Practice of the National  Association of Securities  Dealers, Inc. (the  "NASD")
and  such other policies as the Trustees of the Trust may determine, the Adviser
may consider sales  of Contracts for  which the Trust  is an investment  option,
together  with sales of shares  of other investment company  clients of MFS Fund
Distributors, Inc., the distributor of shares of the Trust and of the MFS Family
of Funds, as a factor in the selection of broker-dealers to execute each Series'
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 Series' operating expenses (E.G., fees charged by the custodian
of  the Series' assets). For a further  discussion of portfolio trading, see the
SAI.
                              -------------------
 
    The SAI includes a  discussion of other investment  policies and listing  of
specific  investment restrictions which  govern the investment  policies of each
Series. The specific investment  restrictions listed in the  SAI may be  changed
without  shareholder  approval unless  indicated  otherwise (see  the  SAI). The
Series' 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 SERIES
 
    The  Trust's  Board  of  Trustees,   as  part  of  its  overall   management
responsibility,  oversees  various  organizations responsible  for  each Series'
day-to-day management.
 
INVESTMENT ADVISER -- MFS manages each Series pursuant to an Investment Advisory
Agreement with the  Trust on behalf  of each  Series dated April  14, 1994  (the
"Advisory  Agreement"). Under  the Advisory  Agreement, MFS  provides the Series
with overall  investment advisory  services.  Subject to  such policies  as  the
Trustees  may determine, MFS makes investment decisions for each Series. For its
services and  facilities,  MFS receives  a  management fee,  computed  and  paid
monthly,  in an amount equal to the  following annual rates of the average daily
net assets of each Series:
 
<TABLE>
<CAPTION>
                                                                                                 PERCENTAGE OF THE
                                                                                                 AVERAGE DAILY NET
                                                                                                       ASSETS
SERIES                                                                                             OF EACH SERIES
- ---------------------------------------------------------------------------------------------  ----------------------
<S>                                                                                            <C>
Emerging Growth Series.......................................................................             0.75%
Research Series..............................................................................             0.75%
Total Return Series..........................................................................             0.75%
Utilities Series.............................................................................             0.75%
World Governments Series.....................................................................             0.75%
Bond Series..................................................................................             0.60%
</TABLE>
 
                                       24
<PAGE>
    MFS or its affiliates will pay a  fee to Kansas City Life Insurance  Company
equal,  on an  annualized basis, to  0.15% of  the aggregate net  assets of each
Series, attributable to Contracts  offered by separate  accounts of Kansas  City
Life  Insurance Company or their  affiliates. Such fees will  not be paid by the
Series, their shareholders, or by the Contract holders.
 
    For the fiscal  year ended  December 31,  1996, MFS  received the  following
management  fees from  the Series under  the Advisory Agreement  and assumed the
following amounts of the Series' expenses (see "Expenses" below);
 
<TABLE>
<CAPTION>
                                                                                    MANAGEMENT FEE  EXPENSES ASSUMED
SERIES                                                                               PAID TO MFS         BY MFS
- ----------------------------------------------------------------------------------  --------------  ----------------
<S>                                                                                 <C>             <C>
Emerging Growth Series............................................................    $  314,262       $   62,962
Research Series...................................................................        92,348           56,859
Total Return Series...............................................................        60,979           87,721
Utilities Series..................................................................        39,863           91,877
World Governments Series..........................................................       126,898          172,556
Bond Series.......................................................................         2,924           40,829
</TABLE>
 
    The identity and background of the portfolio managers for each Series is set
forth below. Unless  indicated otherwise,  each portfolio manager  has acted  in
that capacity since the commencement of investment operations of each Series.
 
<TABLE>
<CAPTION>
SERIES                                                           PORTFOLIO MANAGERS
- -----------------------------  --------------------------------------------------------------------------------------
<S>                            <C>
Emerging Growth Series         John  W. Ballen, a Senior Vice President of MFS, has been employed by the Adviser as a
                               portfolio manager since  1984. Toni  Y. Shimura,  a Vice  President of  MFS, has  been
                               employed  by  the Adviser  as a  portfolio manager  since 1987.  Ms. Shimura  became a
                               portfolio manager of the Series on November 30, 1995.
Research Series                The Series  is  currently managed  by  a  committee comprised  of  various  investment
                               research analysts.
Total Return Series            David  M. Calabro,  a Vice President  of MFS,  has been employed  by the  Adviser as a
                               portfolio manager since  1992. Mr. Calabro  is the head  of this portfolio  management
                               team  and a manager of the common stock  portion of the Series' portfolio. Geoffrey L.
                               Kurinsky, a  Senior Vice  President of  MFS, has  been employed  by the  Adviser as  a
                               portfolio  manager since 1987. Mr. Kurinsky is the manager of the Series' fixed income
                               securities. Judith N. Lamb, a Vice President of MFS, has been employed by the  Adviser
                               as  a portfolio manager since 1992. Ms. Lamb is the manager of the Series' convertible
                               securities. Lisa B. Nurme, a Vice President  of MFS, has been employed by the  Adviser
                               as  a portfolio manager since 1987. Ms. Nurme is a manager of the common stock portion
                               of the Series'  portfolio. Maura A.  Shaughnessy, a  Vice President of  MFS, has  been
                               employed  by  the Adviser  as a  portfolio manager  since 1991.  Ms. Shaughnessy  is a
                               manager of the common stock portion of the Series' portfolio. Each individual became a
                               portfolio manager of the Series on July 19, 1995.
Utilities Series               Maura A.  Shaughnessy, a  Vice President  of the  Adviser, has  been employed  by  the
                               Adviser as a portfolio manager since 1991.
World Governments Series       Stephen  C. Bryant, a Senior  Vice President of the Adviser,  has been employed by the
                               Adviser as a portfolio manager since 1987.
Bond Series                    Geoffrey L. Kurinsky, a Senior Vice President of the Adviser, has been employed by the
                               Adviser as a portfolio manager since 1987.
</TABLE>
 
    MFS also serves as investment adviser to each of the other funds in the  MFS
Family  of Funds  (the "MFS Funds")  and to  MFS-Registered Trademark- 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 Union  Standard 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.) ("Sun Life of
Canada  (U.S.)") in connection  with the sale  of various fixed/variable annuity
contracts. MFS  and its  wholly owned  subsidiary, MFS  Institutional  Advisers,
Inc., provide investment advice to substantial private clients.
 
                                       25
<PAGE>
    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  $52.8  billion on  behalf of  approximately 2.3  million investor
accounts as of February 28, 1997. As of such date, the MFS organization  managed
approximately  $28.9  billion  of  assets  invested  in  equity  securities  and
approximately $19.9  billion  of assets  invested  in fixed  income  securities.
Approximately  $4.0  billion  of  the  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 of Canada  (U.S.), which in turn is  a
wholly  owned subsidiary of  Sun Life Assurance Company  of Canada ("Sun Life").
The Directors of MFS are A. Keith  Brodkin, Jeffrey L. Shames, Arnold D.  Scott,
John D. McNeil and Donald A. Stewart. Mr. Brodkin is the Chairman, Mr. Shames is
the  President  and Mr.  Scott  is the  Secretary  and a  Senior  Executive Vice
President of MFS.  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
United States since 1895, establishing a  headquarters office here in 1973.  The
executive officers of MFS report to the Chairman of Sun Life.
 
    A.  Keith Brodkin, the Chairman  and a Director of  MFS, is the Chairman and
President and a Trustee of the Trust. W. Thomas London, Stephen E. Cavan,  James
R.  Bordewick, Jr.,  and James  O. Yost, all  of whom  are officers  of MFS, are
officers of the Trust.
 
    MFS has established a strategic alliance with Foreign & Colonial  Management
Ltd.  ("Foreign & Colonial"). Foreign  & Colonial is a  subsidiary of two of the
world's oldest  financial  services  institutions, the  London-based  Foreign  &
Colonial Investment Trust PLC, which pioneered the idea of investment management
in  1868, and HYPO-BANK (Bayerische Hypotheken-und Weschsel-Bank AG), the oldest
publicly listed bank in Germany, founded in 1835. As part of this alliance,  the
portfolio  managers and investment analysts of  MFS and Foreign & Colonial share
their views on  a variety  of investment related  issues, such  as the  economy,
securities   markets,  portfolio   securities  and   their  issuers,  investment
recommendations, strategies and  techniques, risk  analysis, trading  strategies
and  other  portfolio  management  matters.  MFS  has  access  to  the extensive
international equity investment expertise of  Foreign & Colonial, and Foreign  &
Colonial  has access to  the extensive U.S. equity  investment expertise of MFS.
MFS and Foreign Colonial each have investment personnel working in each  other's
offices in Boston and London, respectively.
 
    In  certain  instances there  may  be securities  which  are suitable  for a
Series' portfolio as well as for portfolios  of other clients of MFS or  clients
of  Foreign  &  Colonial.  Some simultaneous  transactions  are  inevitable when
several clients  receive investment  advice  from MFS  and Foreign  &  Colonial,
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 a Series  is concerned, in other cases,
however, it may produce increased investment opportunities for the Series.
 
    From time to time, the Adviser  may purchase, redeem and exchange shares  of
any  Series. The  purchase by  the Adviser of  shares of  a Series  may have the
effect of  lowering that  Series' expense  ratio, while  the redemption  by  the
Adviser  of shares of  a Series may  have the effect  of increasing that Series'
expense ratio.
 
    DISTRIBUTOR  --  MFS  Fund  Distributors,  Inc.  ("MFD"),  a  wholly   owned
subsidiary  of MFS, is the distributor of  shares of each Series and also serves
as distributor for certain of the other mutual funds managed by MFS.
 
    ADMINISTRATOR  --  MFS  provides  the  Series  with  certain  administrative
services  pursuant to a Master Administrative  Services Agreement dated March 1,
1997. Under  this Agreement,  MFS provides  the Series  with certain  financial,
legal, compliance, shareholder communications and other administrative services.
As  a partial reimbursement for the cost of providing these services, the Series
pays MFS an administrative  fee up to  0.015% per annum  of the Series'  average
daily  net assets,  provided that  the administrative fee  is not  assessed on a
Series' assets that exceed $3 billion.
 
    SHAREHOLDER SERVICING AGENT  -- MFS Service  Center, Inc. (the  "Shareholder
Servicing  Agent"), a wholly owned subsidiary  of MFS, performs transfer agency,
certain dividend disbursing agency and other services for each Series.
 
                                       26
<PAGE>
8.  INFORMATION CONCERNING SHARES OF EACH SERIES
 
PURCHASES AND REDEMPTIONS
 
    The separate accounts of the Participating Insurance Companies place  orders
to  purchase and redeem shares of each  Series based on, among other things, the
amount of premium payments to be invested and surrender and transfer requests to
be effected on that day pursuant to Contracts. Orders received by the Trust  are
effected  on days on which the Exchange is open for trading. For orders received
by the Trust before  the close of  regular trading on  the Exchange (normally  4
p.m.  eastern time), such purchases and redemptions of the shares of each Series
are effected at the respective net asset  values per share determined as of  the
close  of  regular  trading on  the  Exchange  on that  same  day. Participating
Insurance Companies shall be the designee  of the Trust for receipt of  purchase
and  redemption orders from Contract holders  and receipt by such designee shall
constitute receipt by the Trust; provided that the Trust receives notice of such
order by 9:30 a.m. eastern time on the next following day on which the  Exchange
is open for trading. Payment for shares shall be by federal funds transmitted by
wire and must be received by 2:00 p.m. eastern time on the next following day on
which  the Exchange is  open for trading  after the purchase  order is received.
Redemption proceeds shall be by federal  funds transmitted by wire and shall  be
sent  by 2:00 p.m. eastern time on the  next following day on which the Exchange
is open for trading after  the redemption order is  received. No fee is  charged
the shareholders when they redeem Series shares.
 
    The  offering of shares of any Series may  be suspended for a period of time
and each  Series reserves  the  right to  refuse  any specific  purchase  order.
Purchase  orders may be refused if, in the Adviser's opinion, they are of a size
that would disrupt the management of a  Series. The Trust may suspend the  right
of  redemption of shares of any Series  and may postpone payment for any period:
(i) during which the Exchange is closed other than customary weekend and holiday
closings or during which  trading on the Exchange  is restricted; (ii) when  the
SEC  determines  that a  state of  emergency  exists which  may make  payment or
transfer not reasonably practicable;  (iii) as the SEC  may by order permit  for
the  protection of the security  holders of the Trust; or  (iv) at any time when
the Trust may, under applicable laws, rules and regulations, suspend payment  on
the redemption of its shares.
 
    Should  any conflict between Contract holders arise which would require that
a substantial  amount  of net  assets  be  withdrawn from  any  Series,  orderly
portfolio  management  could be  disrupted to  the  potential detriment  of such
Contract.
 
NET ASSET VALUE
 
    The net asset value per share of  each Series 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 Series' liabilities from  the value of the Series' assets and
dividing the  difference by  the number  of shares  of the  Series  outstanding.
Values  of assets in  a Series' portfolio  are determined on  the basis of their
market or other fair value, as described in the SAI. All investments, assets and
liabilities are expressed in U.S.  dollars based upon current currency  exchange
rates.
 
DISTRIBUTIONS
 
    Substantially  all of  each Series' net  investment income  for any calendar
year is declared as dividends  and paid to its  shareholders as dividends on  an
annual basis. In addition, each Series 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 to its shareholders from short-term  capital
gains.  In determining the  net investment income  available for distribution, a
Series may rely on projections of  its anticipated net investment income  (which
may  include  short-term capital  gains from  the sales  of securities  or other
assets, and,  if allowed  by a  Series' investment  restrictions, premiums  from
options  written), over  a longer  term, rather  than its  actual net investment
income for the period.
 
    Shareholders of any of the Series may elect to receive dividends and capital
gain distributions in either cash or additional shares.
 
TAX STATUS
 
    Each Series of the Trust is treated as a separate entity for federal  income
tax  purposes. In  order to  minimize the taxes  each Series  would otherwise be
required to  pay, each  Series 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 Series  intends to distribute all of its  net
investment  income and net capital gains  to its shareholders in accordance with
the timing requirements imposed by the Code, it is not expected that any of  the
Series will be required to pay entity level federal income or excise taxes.
 
                                       27
<PAGE>
    Shares  of  the  Series  are offered  only  to  the  Participating Insurance
Companies' separate accounts  that fund Contracts.  See the applicable  Contract
prospectus  for a  discussion of  the federal  income tax  treatment of  (1) the
separate accounts that purchase  and hold Series shares  and (2) the holders  of
the  Contracts  that  are funded  through  those  accounts. In  addition  to the
diversification requirements  of Subchapter  M  of the  Code, each  Series  also
intends  to diversify its assets as required  by Code Section 817(h)(1), and the
regulations thereunder. See also "Tax Status" in the SAI.
 
DESCRIPTION OF SHARES, VOTING RIGHTS AND LIABILITIES
 
    Each Series currently has one class of shares, entitled 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  attributable to that  class of that  particular series. Shareholders are
entitled to one vote for each share held, and shares of each Series are entitled
to vote  separately to  approve  investment advisory  agreements or  changes  in
investment  restrictions with respect  to that Series, but  shares of all Series
vote together  in  the  election  of  Trustees  and  selection  of  accountants.
Additionally,  each Series will vote separately on any other matter that affects
solely that Series, but  will otherwise vote together  with all other 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 Series represents  an equal proportionate  interest in  the
Series  with each  share, subject to  the liabilities of  the particular Series.
Shares have  no pre-emptive  or conversion  rights. Shares  are fully  paid  and
non-assessable.  Should  a Series  be liquidated,  shareholders are  entitled to
share PRO RATA  in the net  assets available for  distribution to  shareholders.
Shares  will  remain  on  deposit  with  the  Shareholder  Servicing  Agent  and
certificates will not be issued.
 
    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 existed (E.G., fidelity bonding and omission insurance) and
the Trust itself was unable to meet its obligations.
 
    United  of  Omaha Life  Insurance  Company, Omaha,  NE,  owns 50.75%  of the
Research Series' shares and 33.02% of the World Governments Series' shares, and,
therefore, controls  such  Series;  CG Variable  Annuity--Separate  Account  II,
Hartford, CT, owns 44.85% of the Total Return Series and 29.08% of the Utilities
Series'  shares, and, therefore,  controls such Series;  Ameritas Life Insurance
Company--Separate Account  VA-2  (Annuity),  Lincoln, NE,  owns  56.16%  of  the
Utilities  Series' shares, and, therefore, controls  the Series; Century Life of
America--Century Variable Annuity Account, Waverly, IA, owns 45.82% of the World
Governments Series' shares, and, therefore, controls the Series; and Kansas City
Life Insurance Company--Variable Annuity,  Kansas City, MO,  owns 70.43% of  the
Bond Series' shares, and, therefore, controls the Series.
 
PERFORMANCE INFORMATION
 
    Each  Series' performance may be quoted in advertising in terms of yield and
total return. Performance is based on historical results and is not intended  to
indicate future performance. Performance quoted for a Series includes the effect
of  deducting that  Series' expenses, but  may not include  charges and expenses
attributable to any particular insurance  product. Excluding these charges  from
quotations of a Series' performance has the effect of increasing the performance
quoted. Performance for a Series will vary based on, among other things, changes
in  market conditions, the level of interest  rates and the level of the Series'
expenses. For further information about  the Series' performance for the  fiscal
year  ended December 31, 1996, please see  the Series' Annual Reports. A copy of
these  Annual  Reports  may  be  obtained  without  charge  by  contacting   the
Shareholder Servicing Agent (see back cover for address and phone number).
 
    From  time to time,  quotations of a  Series' total return  and yield may be
included in  advertisements,  sales literature  or  reports to  shareholders  or
prospective investors. The total return of a Series refers to return assuming an
investment  has been held  in the Series  for one year  and for the  life of the
Series (the ending date  of which will be  stated). The total return  quotations
may  be expressed in terms  of average annual or  cumulative rates of return for
all periods quoted.  Average annual total  return refers to  the average  annual
compound  rate of return of  an investment in a  Series. Cumulative total return
represents the cumulative  change in value  of an investment  in a Series.  Both
will  assume that all dividends and capital gains distributions were reinvested.
The yield of a Series refers to net investment income generated by a Series over
a specified 30-day (or one month) period. This income is then "annualized." That
is, the amount  of income generated  by the  Series during that  30-day (or  one
month)  period is assumed to be generated over a 12-month period and is shown as
a percentage of net asset value.
 
                                       28
<PAGE>
EXPENSES
 
    The Trust pays the compensation of the Trustees who are not officers of  MFS
and  all expenses of each Series (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 each Series; fees and expenses of
independent auditors, of legal counsel, and of any transfer agent, registrar  or
dividend disbursing agent of each Series; expenses of repurchasing and redeeming
shares  and servicing shareholder accounts;  expenses of preparing, printing and
mailing  prospectuses,  periodic  reports,  notices  and  proxy  statements   to
shareholders  and 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 Investors Bank &
Trust Company, the Trust's Custodian, for all services to each Series, including
safekeeping of funds and securities and maintaining required books and accounts;
expenses  of  calculating the  net asset  value  of shares  of each  Series; and
expenses  of   shareholder  meetings.   Expenses  relating   to  the   issuance,
registration  and qualification  of shares of  each Series  and the preparation,
printing and mailing of  prospectuses are borne by  each Series except that  the
Distribution Agreement with MFD requires MFD to pay for prospectuses that are to
be  used for sales purposes. Expenses of the Trust which are not attributable to
a specific  Series are  allocated between  the Series  in a  manner believed  by
management of the Trust to be fair and equitable.
 
    Subject  to termination or revision  at the sole discretion  of MFS, MFS has
agreed to bear expenses of each of  the Series such that the respective  Series'
"Other Expenses," which are defined to include all expenses of the Series except
for  management fees,  do not  exceed the  following percentages  of the average
daily net assets of  the Series (the "Maximum  Percentage"): 0.40% for the  Bond
Series  and 0.25% for each remaining Series. The obligation of MFS to bear these
expenses for a Series terminates on the  last day of the Series' fiscal year  in
which its "Other Expenses" are less than or equal to the Maximum Percentage. The
payments made by MFS on behalf of each Series under this arrangement are subject
to reimbursement by the Series to MFS, which will be accomplished by the payment
of  an expense reimbursement fee by the  Series to MFS computed and paid monthly
at a percentage of  the Series' average  daily net assets  for its then  current
fiscal  year, with a limitation that  immediately after such payment the Series'
"Other  Expenses"  will  not  exceed   the  Maximum  Percentage.  This   expense
reimbursement  by each Series  to MFS terminates  on the earlier  of the date on
which payments made by the Series  equal the prior payment of such  reimbursable
expenses by MFS or December 31, 2004.
 
SHAREHOLDER COMMUNICATIONS
 
    Owners  of Contracts issued  by Participating Insurance  Companies for which
shares of one or more  Series are the investment  vehicle will receive from  the
Participating  Insurance Companies semi-annual  financial statements and audited
year-end financial  statements certified  by the  Trust's independent  certified
public accountants. Each report will show the investments owned by the Trust and
the  valuations thereof  as determined  by the  Trustees and  will provide other
information about the Trust and its operations.
 
    Participating Insurance  Companies with  inquiries regarding  the Trust  may
call  the Trust's Shareholder  Servicing Agent. (See back  cover for address and
phone number.)
 
                              -------------------
 
    The SAI for the Trust,  dated May 1, 1997,  as amended or supplemented  from
time  to  time, contains  more detailed  information about  each of  the Series,
including information related to: (i)  the investment policies and  restrictions
of each Series; (ii) the Trustees, officers and investment adviser of the Trust;
(iii)  portfolio transactions; (iv) the shares  of each Series, including rights
and liabilities of  shareholders; (v)  the method  used to  calculate yield  and
total  rate of return quotations  of each Series; (vi)  the determination of net
asset value  of  shares of  each  Series; and  (vii)  certain voting  rights  of
shareholders of each Series.
 
                                       29
<PAGE>
                                                                      APPENDIX A
 
                          DESCRIPTION OF BOND RATINGS
 
The ratings of Moody's, S&P and Fitch represent their opinions as to the quality
of  various debt instruments. It should be emphasized, however, that ratings are
not absolute standards of quality. Consequently, debt instruments with the  same
maturity,  coupon and rating may have different yields while debt instruments of
the same maturity and coupon with different ratings may have the same yield.
 
                        MOODY'S INVESTORS SERVICE, INC.
 
    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  fluctuations  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.
 
    BA:  Bonds which are rated Ba are judged to have speculative elements; their
future cannot be considered  as well-assured. Often  the protection of  interest
and  principal payments  may be very  moderate and thereby  not well safeguarded
during both  good  and  bad  times over  the  future.  Uncertainty  of  position
characterizes bonds in this class.
 
    B:  Bonds which are rated B  generally lack characteristics of the desirable
investment. Assurance of interest  and principal payments  or of maintenance  of
other terms of the contract over any long period of time may be small.
 
    CAA:  Bonds which are rated Caa are of  poor standing. Such issues may be in
default or there may be present elements of danger with respect to principal  or
interest.
 
    CA:  Bonds which are rated Ca represent obligations which are speculative in
a  high  degree.  Such  issues  are  often  in  default  or  have  other  marked
shortcomings.
 
    C: Bonds which are rated C are the lowest rated class of bonds and issues so
rated  can be regarded as having extremely  poor prospects of ever attaining any
real investment standing.
 
    ABSENCE OF RATING: Where no rating has  been assigned or where a rating  has
been  suspended or withdrawn, it may be  for reasons unrelated to the quality of
the issue.
 
    Should no rating be assigned, the reason may be one of the following:
 
    1.  an application for rating was not received or accepted;
 
    2.  the issue or issuer belongs  to a group of securities or companies  that
       are not rated as a matter of policy;
 
    3.  there is a lack of essential data pertaining to the issue or issuer; or
 
    4.    the  issue was  privately  placed, in  which  case the  rating  is not
       published in Moody's publications.
 
                                      A-1
<PAGE>
    Suspension or withdrawal may occur if new and material circumstances  arise,
the  effects  of which  preclude satisfactory  analysis; if  there is  no longer
available reasonable up-to-date  data to permit  a judgment to  be formed; if  a
bond is called for redemption; or for other reasons.
 
                       STANDARD & POOR'S RATINGS SERVICES
 
    AAA:  Debt rated AAA has the highest rating assigned by S&P. Capacity to pay
interest and repay principal is extremely strong.
 
    AA: Debt rated  AA has  a very  strong capacity  to pay  interest and  repay
principal and differs from the highest rated issues only in small degree.
 
    A:  Debt rated A has a strong  capacity to pay interest and repay principal,
although it is somewhat  more susceptible to the  adverse effects of changes  in
circumstances and economic conditions than debt in higher-rated categories.
 
    BBB:  Debt  rated BBB  is regarded  as  having an  adequate capacity  to pay
interest and repay principal. Whereas  it normally exhibits adequate  protection
parameters,  adverse  economic  conditions or  changing  circumstances  are more
likely to lead to a  weakened capacity to pay  interest and repay principal  for
debt in this category than in higher-rated categories.
 
    BB:  Debt rated  BB has less  near-term vulnerability to  default than other
speculative issues. However, it faces major ongoing uncertainties or exposure to
adverse  business,  financial,  or  economic  conditions  which  could  lead  to
inadequate  capacity  to meet  timely interest  and  principal payments.  The BB
rating category  is also  used for  debt  subordinated to  senior debt  that  is
assigned an actual or implied BBB- rating.
 
    B: Debt rated B has a greater vulnerability to default but currently has the
capacity  to meet interest payments  and principal repayments. Adverse business,
financial or economic conditions will  likely impair capacity or willingness  to
pay  interest and repay principal.  The B rating category  is also used for debt
subordinated to senior  debt that is  assigned an  actual or implied  BB or  BB-
rating.
 
    CCC:  Debt rated CCC has a  currently identifiable vulnerability to default,
and is dependent upon favorable  business, financial and economic conditions  to
meet  timely payment  of interest  and repayment of  principal. In  the event of
adverse business, financial, or  economic conditions, it is  not likely to  have
the  capacity to pay  interest and repay  principal. The CCC  rating category is
also used for debt  subordinated to senior  debt that is  assigned an actual  or
implied B or B- rating.
 
    CC:  The rating CC is typically applied  to debt subordinated to senior debt
that is assigned an actual or implied CCC rating.
 
    C: The rating  C is typically  applied to debt  subordinated to senior  debt
which  is assigned an  actual or implied CCC-  debt rating. The  C rating may be
used to cover a situation where a  bankruptcy petition has been filed, but  debt
service payments are continued.
 
    CI: The rating CI is reserved for income bonds on which no interest is being
paid.
 
    D:  Debt rated D is  in payment default. The D  rating category is used when
interest payments or principal payments  are not made on  the date due, even  if
the  applicable  grace period  has not  expired, unless  S&P 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  if  debt  service  payments  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  within the major
rating categories.
 
    NR: Indicates  that no  public  rating has  been  requested, that  there  is
insufficient  information on which to base a rating, or that S&P does not rate a
particular type of obligation as a matter of policy.
 
A-1 AND P-1 COMMERCIAL PAPER RATINGS
 
Description of S&P, Fitch and Moody's highest commercial paper ratings:
 
    The rating "A" is  the highest commercial paper  rating assigned by S&P  and
Fitch,  and issues  so rated  are regarded as  having the  greatest capacity for
timely payment. Issues in the "A" category are delineated with the numbers 1,  2
and 3 to
 
                                      A-2
<PAGE>
indicate  the relative degree of safety.  The A-1 designation indicates that the
degree of safety regarding timely payment is either overwhelming or very strong.
Those A-1 issues determined to possess overwhelming 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 have a superior ability for repayment. P-1 repayment  capacity
will  normally be evidenced by 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;  and (5) well  established
access  to  a  range  of  financial markets  and  assured  sources  of alternate
liquidity.
 
                         FITCH INVESTORS SERVICE, INC.
 
    AAA: Bonds  considered to  be investment  grade and  of the  highest  credit
quality.  The obligor  has an exceptionally  strong ability to  pay interest and
prepay principal, which  is unlikely  to be affected  by reasonably  foreseeable
events.
 
    AA: Bonds considered to be investment grade and of very high credit quality.
The  obligor's  ability to  pay  interest and  repay  principal is  very strong,
although not quite as strong  as bonds rated 'AAA'.  Because bonds rated in  the
'AAA' and 'AA' categories are not significantly vulnerable to foreseeable future
developments, short-term debt of these issuers is generally rated 'F-1+'.
 
    A:  Bonds considered to be investment grade and of very high credit quality.
The obligor's ability to  pay interest and repay  principal is considered to  be
strong, but may be more vulnerable to adverse changes in economic conditions and
circumstances than bonds with higher ratings.
 
    BBB:  Bonds considered  to be  investment grade  and of  satisfactory credit
quality. The obligor's ability to pay interest and repay principal is considered
to be  adequate.  Adverse  changes in  economic  conditions  and  circumstances,
however,  are more likely to have adverse  impact on these bonds and, therefore,
impair timely payment. The likelihood that the ratings of these bonds will  fall
below investment grade is higher than for bonds with higher ratings.
 
    BB:  Bonds are considered speculative. The obligor's ability to pay interest
and repay  principal may  be affected  over time  by adverse  economic  changes.
However,  business  and financial  alternatives  can be  identified  which could
assist the obligor in satisfying its debt service requirements.
 
    B: Bonds are considered  highly speculative. While bonds  in this class  are
currently meeting debt service requirements, the probability of continued timely
payment  of  principal and  interest reflects  the  obligor's limited  margin of
safety and the need for reasonable business and economic activity throughout the
life of the issue.
 
    CCC: Bonds have certain identifiable characteristics which, if not remedied,
may lead to default.  The ability to meet  obligations requires an  advantageous
business and economic environment.
 
    CC:  Bonds are  minimally protected. Default  in payment  of interest and/or
principal seems probable over time.
 
    C: Bonds are in imminent default in payment of interest of principal.
 
    PLUS(+) MINUS(-): Plus  and minus  signs are used  with a  rating symbol  to
indicate  the relative position of a credit  within the rated category. Plus and
minus signs, however, are not used in the 'AAA' category.
 
    NR: indicates that Fitch does not rate the specific issue.
 
    CONDITIONAL: A conditional rating is  premised on the successful  completion
of a project or the occurrence of a specific event.
 
    SUSPENDED:  A rating is suspended when Fitch deems the amount of information
available from the issuer to be inadequate for rating purposes.
 
    WITHDRAWN: A rating will be withdrawn when an issue matures or is called  or
refinanced,  and, at Fitch's discretion, when  an issuer fails to furnish proper
and timely information.
 
                                      A-3
<PAGE>
    FITCHALERT: Ratings  are placed  on  FitchAlert to  notify investors  of  an
occurrence  that is likely to result in a rating change and the likely direction
of such  change.  These are  designated  a "Positive,"  indicating  a  potential
upgrade,  "Negative," for potential downgrade,  or "Evolving," where ratings may
be lowered. FitchAlert is relatively short-term and should be resolved within 12
months.
                        DUFF & PHELPS CREDIT RATING CO.
 
    AAA: Bonds  considered to  be investment  grade and  of the  highest  credit
quality.  The obligor  has an exceptionally  strong ability to  pay interest and
repay principal,  which is  unlikely to  be affected  by reasonably  foreseeable
events.
 
    AA: Bonds considered to be investment grade and or very high credit quality.
The  obligor's  ability to  pay  interest and  repay  principal is  very strong,
although not quite as strong  as bonds rated 'AAA'.  Because bonds rated in  the
'AAA' and 'AA' categories are not significantly vulnerable to foreseeable future
developments, short-term debt of these issuers is generally rated 'D-1+'.
 
    A:  Bonds considered to be investment grade  and of high credit quality. The
obligor's ability  to pay  interest  and repay  principal  is considered  to  be
strong, but may be more vulnerable to adverse changes in economic conditions and
circumstances than bonds with higher ratings.
 
    BBB:  Bonds considered  to be  investment grade  and of  satisfactory credit
quality. The obligor's ability to pay interest and repay principal is considered
to be  adequate.  Adverse  changes in  economic  conditions  and  circumstances,
however,  are more likely to  have adverse impact on  these bonds, and therefore
impair timely payment. The likelihood that the ratings of these bonds will  fall
below investment grade is higher than for bonds with higher ratings.
 
    BB:  Bonds are considered speculative. The obligor's ability to pay interest
and repay  principal may  be affected  over time  by adverse  economic  changes.
However,  business,  and financial  alternatives can  be identified  which could
assist the obligor in satisfying its debt service requirements.
 
    B: Bonds are considered  highly speculative. While bonds  in this class  are
currently meeting debt service requirements, the probability of continued timely
payment  of  principal and  interest reflects  the  obligor's limited  margin of
safety and the need for reasonable business and economic activity throughout the
life of the issue.
 
    CCC: Bonds have certain identifiable characteristics which, if not remedied,
may lead to default.  The ability to meet  obligations requires an  advantageous
business and economic environment.
 
    PLUS (+) OR MINUS (-): Plus and minus signs are used with a rating symbol to
indicate  the relative position of  a credit within a  rating category. Plus and
minus signs, however, are not used in the 'AAA' category.
 
    NR: Indicates that Duff & Phelps does not rate the specific issue.
 
                        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.
 
    D-1:  Very high certainty of timely payment. Liquidity factors are excellent
and supported by good fundamental protection factors. Risk factors are minor.
 
    D-1-: High certainty  of timely  payment. Liquidity factors  are strong  and
supported by good fundamental protection factors. Risk factors are very small.
 
    D-2:  Good  certainty  of  timely  payment.  Liquidity  factors  and company
fundamentals are  sound.  Although  ongoing  funding  needs  may  enlarge  total
financing  requirements, access  to capital  markets is  good. Risk  factors are
small.
 
    D-3: Satisfactory liquidity and other  protection factors qualify issues  as
to  investment grade.  Risk factors  are larger  and subject  to more variation.
Nevertheless, timely payment is expected.
 
    D-4: Speculative investment characteristics. Liquidity is not sufficient  to
insure  against disruption in debt service.  Operating factors and market access
may be subject to a high degree of variation.
 
    D-5: Issuer failed to meet scheduled principal and/or interest payments.
 
                                      A-4
<PAGE>
                                                                      APPENDIX B
 
                  PRINCIPAL SECTORS OF THE UTILITIES INDUSTRY
 
The principal sectors of the utility industry in which the Utilities Series  may
invest are discussed below.
 
ELECTRIC -- The electric utility industry consists of companies that are engaged
principally  in  the  generation,  transmission  and  sale  of  electric energy,
although many  also provide  other  energy-related services.  Domestic  electric
utility  companies, in general,  recently have been  favorably affected by lower
fuel and financing costs and the  full or near completion of major  construction
programs.  In addition,  many of  these companies  recently have  generated cash
flows in excess  of current  operating expenses  and construction  expenditures,
permitting  some  degree of  diversification  into unregulated  businesses. Some
electric utilities have also taken advantage of the right to sell power  outside
of  their traditional geographic areas.  Electric utility companies historically
have been  subject to  the risks  associated with  increases in  fuel and  other
operating   costs,  high  interest  costs   on  borrowings  needed  for  capital
construction programs, costs associated  with compliance with environmental  and
safety regulations and changes in the regulatory climate.
 
    In  the U.S., the construction and  operation of nuclear power facilities is
subject to  increased scrutiny  by,  and evolving  regulations of,  the  Nuclear
Regulatory   Commission  and  state  agencies  having  comparable  jurisdiction.
Increased scrutiny might  result in  higher operating costs  and higher  capital
expenditures,  with the risk that the regulators may disallow inclusion of these
costs in rate authorizations or the risk that a company may not be permitted  to
operate  or  complete  construction of  a  facility. In  addition,  operators of
nuclear power plants may be subject to significant costs for disposal of nuclear
fuel and for the de-commissioning of such plants.
 
TELECOMMUNICATIONS -- The telephone industry  is large and highly  concentrated.
Companies that distribute telephone services and provide access to the telephone
networks  comprise the greatest portion of  this segment. Telephone companies in
the U.S. are still experiencing the effects of the breakup of American Telephone
& Telegraph Company, which  occurred in 1984. Since  1984, companies engaged  in
telephone  communication services  have expanded  their non-regulated activities
into other businesses, including  cellular telephone services, data  processing,
equipment  retailing,  computer software  and  hardware services,  and financial
services. This  expansion has  provided  significant opportunities  for  certain
telephone  companies to  increase their earnings  and dividends  at faster rates
than  had  been  allowed  in  traditionally  regulated  businesses.   Increasing
competition,  technological innovations  and other  structural changes, however,
could adversely affect the profitability of such utilities.
 
GAS --  Gas  transmission companies  and  gas distribution  companies  are  also
undergoing  significant changes. In the  U.S., interstate transmission companies
are regulated by the Federal Energy Regulatory Commission, which is reducing its
regulation of the  industry. Many companies  have diversified into  oil and  gas
exploration  and development, making returns more sensitive to energy prices. In
the recent  decade,  gas  utility  companies have  been  adversely  affected  by
disruptions  in  the  oil industry  and  have  also been  affected  by increased
concentration  and  competition.  In  the  opinion  of  the  Adviser,   however,
environmental  considerations  could improve  the  gas industry  outlook  in the
future. For example, natural gas is  the cleanest of the hydrocarbon fuels,  and
this may result in incremental shifts in fuel consumption toward natural gas and
away from oil and coal.
 
WATER  -- Water supply utilities are  companies that collect, purify, distribute
and sell  water. In  the  U.S. and  around the  world,  the industry  is  highly
fragmented  because  most  of  the  supplies  are  owned  by  local authorities.
Companies in this industry are generally  mature and are experiencing little  or
no per capita volume growth.
 
                              -------------------
 
    There  can  be  no assurance  that  the positive  developments  noted above,
including those relating to changing regulation, will occur or that risk factors
other than those noted above will not develop in the future.
 
                                      B-1
<PAGE>
                                                                      APPENDIX C
 
                                MFS BOND SERIES
                          PORTFOLIO COMPOSITION CHART
                    FOR FISCAL YEAR ENDED DECEMBER 31, 1996
 
The table below shows the percentages of the Series' assets at December 31, 1996
invested in bonds  assigned to  the various  rating categories  by S&P,  Moody's
(provided  only for bonds not rated by  S&P), Fitch (provided only for bonds not
rated by S&P or Moody's) and Duff & Phelps (provided only for bonds not rated by
S&P, Moody's  or  Fitch)  and in  unrated  bonds  determined by  MFS  to  be  of
comparable  quality. For  split rated  bonds, the higher  of the  S&P or Moody's
rating is used. When  neither an S&P or  Moody's rating is available,  secondary
sources are selected in the following order: Fitch and Duff & Phelps.
 
<TABLE>
<CAPTION>
              COMPILED
RATING         RATINGS      TOTAL
- -----------  -----------  ----------
<S>          <C>          <C>         <C>
AAA/Aaa           31.50       31.50
AA/Aa              1.69        1.69
A/A                7.61        7.61
BBB/Baa           28.46       28.46
BB/Ba             14.35       14.35
B/B                1.28        1.28
CCC/Caa
CC/Ca
C/C
Default
                  -----       -----
    TOTAL         84.89       84.89
</TABLE>
 
The  chart does  not necessarily  indicate what  the composition  of the Series'
portfolio will be in subsequent years. Rather, the Series' investment objective,
policies and restrictions indicate the extent  to which the Series may  purchase
securities in the various categories.
 
                                      C-1
<PAGE>
INVESTMENT ADVISER
Massachusetts Financial Services Company
500 Boylston Street, Boston, MA 02116
(617) 954-5000
(800) 637-8730
 
DISTRIBUTOR
MFS Fund Distributors, Inc.
500 Boylston Street, Boston, MA 02116
(617) 954-5000
CUSTODIAN
Investors Bank & Trust Company
89 South Street, Boston, MA 02111
 
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) 343-2829, ext. 3500
MAILING ADDRESS:
P.O. Box 1400, Boston, MA 02104-9985
INDEPENDENT AUDITORS
Deloitte & Touche LLP
125 Summer Street, Boston, MA 02110
 
                                     [LOGO]
 
                MFS-REGISTERED TRADEMARK- EMERGING GROWTH SERIES
                   MFS-REGISTERED TRADEMARK- RESEARCH SERIES
                 MFS-REGISTERED TRADEMARK- TOTAL RETURN SERIES
                   MFS-REGISTERED TRADEMARK- UTILITIES SERIES
               MFS-REGISTERED TRADEMARK- WORLD GOVERNMENTS SERIES
                     MFS-REGISTERED TRADEMARK- BOND SERIES
 
                     500 Boylston Street, Boston, MA 02116
                      ------------------------------------
                MFS-REGISTERED TRADEMARK- EMERGING GROWTH SERIES
 
                   MFS-REGISTERED TRADEMARK- RESEARCH SERIES
 
                        MFS-REGISTERED TRADEMARK- TOTAL
                                 RETURN SERIES
 
                   MFS-REGISTERED TRADEMARK- UTILITIES SERIES
 
                        MFS-REGISTERED TRADEMARK- WORLD
                               GOVERNMENTS SERIES
 
                     MFS-REGISTERED TRADEMARK- BOND SERIES
 
                                     [LOGO]
 
                                   PROSPECTUS
 
                                  MAY 1, 1997
 
                            ------------------------


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