MFS VARIABLE INSURANCE TRUST
497, 1997-05-05
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<PAGE>
 
<TABLE>
<S>                                        <C>
MFS-REGISTERED TRADEMARK- TOTAL RETURN
SERIES
MFS-REGISTERED TRADEMARK- UTILITIES
SERIES
MFS-REGISTERED TRADEMARK- WORLD            PROSPECTUS
GOVERNMENTS 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"),  three of which are offered pursuant to  this
Prospectus.
 
- -- 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); and
 
- -- MFS  WORLD GOVERNMENTS SERIES  (the "World Governments  Series"), which seeks
   not only  preservation but  also growth  of capital,  together with  moderate
   current income.
                              -------------------
 
  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................................................................   4
  4.  Investment Objectives and Policies.............................................................   7
      MFS Total Return Series........................................................................   7
      MFS Utilities Series...........................................................................   7
      MFS World Governments Series...................................................................   9
  5.  Investment Techniques..........................................................................  10
  6.  Additional Risk Factors........................................................................  16
  7.  Management of the Series.......................................................................  19
  8.  Information Concerning Shares of Each Series...................................................  21
      Purchases and Redemptions......................................................................  21
      Net Asset Value................................................................................  22
      Distributions..................................................................................  22
      Tax Status.....................................................................................  22
      Description of Shares, Voting Rights and Liabilities...........................................  22
      Performance Information........................................................................  23
      Expenses.......................................................................................  23
      Shareholder Communications.....................................................................  24
  Appendix A -- Description of Bond Ratings..........................................................  A-1
  Appendix B -- Principal Sectors of the Utilities Industry..........................................  B-1
</TABLE>
 
                                       2
<PAGE>
1.  EXPENSE SUMMARY
 
ANNUAL OPERATING EXPENSES (AS A PERCENTAGE OF AVERAGE NET ASSETS):
 
<TABLE>
<CAPTION>
                                                                MFS
                                                               TOTAL       MFS       MFS WORLD
                                                               RETURN    UTILITIES  GOVERNMENTS
                                                               SERIES     SERIES      SERIES
                                                              --------   --------   -----------
<S>                                                           <C>        <C>        <C>
Management Fee..............................................  0.75%      0.75%         0.75%
Other Expenses (after expense limitation)(1)(2).............  0.25%      0.25%         0.25%
                                                              --------    ---       -----------
Total Operating Expenses (after expense limitation)(2)......  1.00%      1.00%         1.00%
</TABLE>
 
- ------------------------
 
<TABLE>
<S>        <C>
(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 0.25% of the average  daily net assets of  the Series during the current
           fiscal year. See "Information Concerning Shares of Each Series--Expenses." Otherwise, "Other Expenses" for the Total
           Return Series, the Utilities Series and the World Governments Series would be 1.35%, 2.00% and 1.28%,  respectively,
           and "Total Operating Expenses" would be 2.10%, 2.75% and 2.03%, respectively, for these Series.
</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.
 
    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.
 
                                       3
<PAGE>
    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.
 
3.  CONDENSED FINANCIAL INFORMATION
 
The following financial information (presented  for each Series which  commenced
investment  operations prior  to December 31,  1996) 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.
 
                              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
</TABLE>
 
- ------------------------
 
<TABLE>
<C>        <S>
        *  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:
</TABLE>
 
<TABLE>
<S>                                                                <C>                         <C>
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>
 
                                       4
<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
</TABLE>
 
- ------------------------
 
<TABLE>
<C>        <S>
        *  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:
</TABLE>
 
<TABLE>
<S>                                                                <C>                         <C>
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>
 
                                       5
<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>
 
                                       6
<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 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
 
                                       7
<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.
 
                                       8
<PAGE>
    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' 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.)
 
                                       9
<PAGE>
    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.
 
    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.
 
5.  INVESTMENT TECHNIQUES
 
    LENDING OF PORTFOLIO SECURITIES: Each of the 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 of  the  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  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  of  the  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.
 
                                       10
<PAGE>
    "WHEN-ISSUED"  SECURITIES: Each of the  Series (except 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  of the  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 of the  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 of the  Total Return Series and the
Utilities  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 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
 
                                       11
<PAGE>
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 of the Series
may  invest in  zero coupon bonds.  The Total  Return 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 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 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  the World  Governments Series  and the  Utilities 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: 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.
 
                                       12
<PAGE>
    LOAN  PARTICIPATIONS AND OTHER DIRECT  INDEBTEDNESS: 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.  The 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 the 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,
the  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 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  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 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, the  World Governments  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 the
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, the  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 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
 
                                       13
<PAGE>
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 of  the  Total  Return Series  and  the  World
Governments  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  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.
 
    OPTIONS ON STOCK INDICES: Each of 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.
 
                                       14
<PAGE>
    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  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 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  the  Series  may  also
purchase  and  write  options on  such  Futures Contracts  ("Options  on Futures
Contracts"). The Total Return Series may purchase and sell Futures Contracts  on
stock  indices, while 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 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  of  the 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  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
 
                                       15
<PAGE>
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 of  the 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.
 
    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  of the Total  Return and the  Utilities 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
 
                                       16
<PAGE>
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 of the 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. All of the 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.
 
    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.
 
                                       17
<PAGE>
    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.
 
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  and the World  Governments 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-
 
                                       18
<PAGE>
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>
Total Return Series..........................................................................             0.75%
Utilities Series.............................................................................             0.75%
World Governments Series.....................................................................             0.75%
</TABLE>
 
    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>
Total Return Series...............................................................    $   60,979       $   87,721
Utilities Series..................................................................        39,863           91,877
World Governments Series..........................................................       126,898          172,556
</TABLE>
 
    MFS or its affiliates will pay a fee to Cigna Individual Insurance ("CIGNA")
equal, on an  annualized basis, to  0.15% of  the aggregate net  assets of  each
Series  up to $200 million and 0.20% of  aggregate net assets of the Series over
$200 million attributable to Contracts offered by separate accounts of CIGNA  or
its affiliates. Such fees will not be paid by the Series, their shareholders, or
by the Contract holders.
 
                                       19
<PAGE>
    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>
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.
</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.
 
    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
 
                                       20
<PAGE>
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.
 
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.
 
                                       21
<PAGE>
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.
 
    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.
 
                                       22
<PAGE>
    United  of Omaha Life Insurance Company, Omaha, NE, owns 33.02% of the World
Governments Series' shares,  and, therefore,  controls the  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;  and Century  Life  of America--Century  Variable  Annuity
Account,  Waverly, IA, owns 45.82% of the World Governments Series' shares, and,
therefore, controls the Series.
 
PERFORMANCE INFORMATION
 
    Each Series' performance may be quoted in advertising in terms of yield and,
except for  the Money  Market  Series, 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.
 
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 0.25% of the average daily net assets of the
Series (the "Maximum Percentage"). 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
 
                                       23
<PAGE>
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.
 
                                       24
<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.
 
                                      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>
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- TOTAL RETURN SERIES
                   MFS-REGISTERED TRADEMARK- UTILITIES SERIES
               MFS-REGISTERED TRADEMARK- WORLD GOVERNMENTS SERIES
                     500 Boylston Street, Boston, MA 02116
 
                      ------------------------------------
 
                 MFS-REGISTERED TRADEMARK- TOTAL RETURN SERIES
                   MFS-REGISTERED TRADEMARK- UTILITIES SERIES
               MFS-REGISTERED TRADEMARK- WORLD GOVERNMENT SERIES
 
                                     [LOGO]
 
                                   PROSPECTUS
 
                                  MAY 1, 1997
                            ------------------------


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