MFS VARIABLE INSURANCE TRUST
497, 1999-08-26
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[LOGO MFS INVESTMENT MANAGEMENT]

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MFS[RegTM] VARIABLE INSURANCE TRUST(SM)
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M A Y   1 ,  1 9 9 9

                                                                     Prospectus

MFS[RegTM] GROWTH WITH INCOME SERIES

MFS[RegTM] TOTAL RETURN SERIES

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

This Prospectus describes two of the series of the MFS Variable Insurance Trust
(referred to as the trust):

1. MFS Growth With Income Series seeks to provide reasonable current income and
   long-term growth of capital and income (referred to as the Growth With
   Income Series); and

2. MFS Total Return Series 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 (referred to as the
   Total Return Series).

The Securities and Exchange Commission has not approved the series' shares or
determined whether this prospectus is accurate or complete. Anyone who tells
you otherwise is committing a crime.
<PAGE>

- -----------------
TABLE OF CONTENTS
- -----------------

<TABLE>
<CAPTION>
                                                                     Page
<S>   <C>                                                           <C>
I     Expense Summary ............................................    (1)

II    Risk Return Summary ........................................    (2)

      1. Growth With Income Series ...............................    (2)

      2. Total Return Series .....................................    (5)

III   Certain Investment Strategies and Risks ....................    (9)

IV    Management of the Series ...................................    (9)

V     Description of Shares ......................................    (9)

VI    Other Information ..........................................   (10)

VII   Financial Highlights .......................................   (11)

      Appendix A -- Investment Techniques and Practices ..........  (A-1)
</TABLE>

<PAGE>

   The trust offers shares of its 15 series to separate accounts established
   by insurance companies in order to serve as investment vehicles for
   variable annuity and variable life insurance contracts and to qualified
   pension and retirement plans. Each of these series is managed by
   Massachusetts Financial Services Company (referred to as MFS or the
   adviser). Two of these series are described below.

- -----------------
I EXPENSE SUMMARY
- -----------------

(>) Expense Table

This table describes the expense that you may pay when you hold shares of the
series. These fees and expenses do not take into account the fees and expenses
imposed by insurance companies through which your investment in a series may be
made.

Annual Series Operating Expenses (expenses that are deducted from a series'
assets):

<TABLE>
<CAPTION>
                                                           Growth
                                                            With         Total
                                                           Income       Return
                                                           Series       Series
                                                         ----------   ----------
   <S>                                                       <C>          <C>
   Management Fee ....................................       0.75%        0.75%
   Other Expenses(1) .................................       0.13%        0.16%
                                                             ----         ----
   Total Annual Series Operating Expenses(1) .........       0.88%        0.91%
</TABLE>

   ---------

   (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. Each series may enter into
       other such arrangements and directed brokerage arrangements, which would
       also have the effect of reducing the series' expenses. Expenses do not
       take into account these expense reductions, and are therefore higher than
       the actual expenses of the series.

   (2) MFS has contractually agreed to bear expenses for these series, subject
       to reimbursement by these series, such that each such series' "Other
       Expenses" shall not exceed 0.25% of the average daily net assets of the
       series during the current fiscal year for each remaining series. The
       payments made by MFS on behalf of each series under this arrangement are
       subject to reimbursement by the series to MFS, which will be accomplished
       by the payment of an expense reimbursement fee by the series to MFS
       computed and paid monthly at a percentage of the series' average daily
       net assets for its then current fiscal year, with a limitation that
       immediately after such payment the series' "Other Expenses" will not
       exceed the percentage set forth above for that series. The obligation of
       MFS to bear a series' "Other Expenses" pursuant to this arrangement, and
       the series' obligation to pay the reimbursement fee 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.
       MFS may, in its discretion, terminate this contractual arrangement at an
       earlier date, provided that the arrangement will continue for each series
       until at least May 1, 2000, unless terminated with the consent of the
       board of trustees which oversees the series.



(>) Example of Expenses

    These examples are intended to help you compare the cost of investing in the
    series with the cost of investing in other mutual funds. These examples do
    not take into account the fees and expenses imposed by insurance companies
    through which your investment in a series may be made.

    The examples assume that:

    o You invest $10,000 in the series for the time periods indicated and you
      redeem your shares at the end of the time periods;

    o Your investment has a 5% return each year and dividends and other
      distributions are reinvested; and

    o The series' operating expenses remain the same.

    Although your actual costs may be higher or lower, under these assumptions
    your costs would be:

<TABLE>
<CAPTION>
                                               Period
                               ---------------------------------------
Series                          1 Year   3 Years   5 Years   10 Years
- ----------------------------------------------------------------------
   <S>                             <C>      <C>       <C>       <C>
   Growth With Income Series       $90      $281      $488      $1,084
   Total Return Series              93       290       504       1,120
</TABLE>


                                       1
<PAGE>

- ----------------------
II RISK RETURN SUMMARY
- ----------------------

    Investment strategies which are common to all series are described under the
    caption "Certain Investment Strategies."


    1: Growth With Income Series
    ........................................................................ .

(>) Investment Objective

    The series' investment objective is to provide reasonable current income and
    long-term growth of capital and income. The series' objective may be changed
    without shareholder approval.


(>) Principal Investment Policies

    The series invests, under normal market conditions, at least 65% of its
    total assets in common stocks and related securities, such as preferred
    stocks, convertible securities and depositary receipts for those securities.
    These securities may be listed on a securities exchange or traded in the
    over-the-counter markets. While the series may invest in companies of any
    size, the series generally focuses on companies with larger market
    capitalizations that MFS believes have sustainable growth prospects and
    attractive valuations based on current and expected earnings or cash flow.

    MFS uses a bottom-up, as opposed to a top-down, investment style in managing
    the equity-oriented funds (such as the series) it advises. This means that
    securities are selected based upon fundamental analysis performed by the
    series' portfolio manager and MFS' large group of equity research analysts.

    The series may invest in foreign equity securities through which it may have
    exposure to foreign currencies.


(>) Principal Risks

    The principal risks of investing in the series and the circumstances
    reasonably likely to cause the value of your investment in the series to
    decline are described below. As with any non-money market mutual fund, the
    share price of the series will change daily based on market conditions and
    other factors. Please note that there are many circumstances which could
    cause the value of your investment in the series to decline, and which could
    prevent the series from achieving its objectives, that are not described
    here.

    The principal risks of investing in the series are:

    o Market Risk: This is the risk that the price of a security held by the
      series will fall due to changing economic, political or market conditions
      or disappointing earnings results.

    o Company Risk: Prices of securities react to the economic condition of the
      company that issued the security. The series' equity investments in an
      issuer may rise and fall based on the issuer's actual and anticipated
      earnings, changes in management and the potential for takeovers and
      acquisitions.

    o Large Cap Companies Risk: Large cap companies tend to go in and out of
      favor based on market and economic conditions. Large cap companies tend to
      be less volatile than companies with smaller market capitalizations. In
      exchange for this potentially lower risk, the series' value may not rise
      as much as the value of series that emphasize smaller cap companies.

    o Foreign Markets Risk: Investing in foreign securities involves risks
      relating to political, social and economic developments abroad, as well as
      risks resulting from the differences between the regulations to which U.S.
      and foreign issuers and markets are subject:

        > These risks may include the seizure by the government of company
          assets, excessive taxation, withholding taxes on dividends and
          interest, limitations on the use or transfer of portfolio assets, and
          political or social instability.

        > Enforcing legal rights may be difficult, costly and slow in foreign
          countries, and there may be special problems enforcing claims against
          foreign governments.

        > Foreign companies may not be subject to accounting standards or
          governmental supervision comparable to U.S. companies, and there may
          be less public information about their operations.

        > Foreign markets may be less liquid and more volatile than U.S.
          markets.

        > Foreign securities often trade in currencies other than the U.S.
          dollar, and the series may directly hold foreign currencies and
          purchase and sell foreign currencies through forward exchange
          contracts. Changes in currency exchange rates will affect the series'
          net asset


                                       2
<PAGE>

          value, the value of dividends and interest earned, and gains and
          losses realized on the sale of securities. An increase in the strength
          of the U.S. dollar relative to these other currencies may cause the
          value of the series to decline. Certain foreign currencies may be
          particularly volatile, and foreign governments may intervene in the
          currency markets, causing a decline in value or liquidity in the
          series' foreign currency holdings. By entering into forward foreign
          currency exchange contracts, the series may be required to forego the
          benefits of advantageous changes in exchange rates and, in the case of
          forward contracts entered into for the purpose of increasing return,
          the series may sustain losses which will reduce its gross income.
          Forward foreign currency exchange contracts involve the risk that the
          party with which the series enters the contract may fail to perform
          its obligations to the series.

    o As with any mutual fund, you could lose money on your investment in the
      series.

    An investment in the series is not a bank deposit and is not insured or
    guaranteed by the Federal Deposit Insurance Corporation or any other
    government agency.


(>) Bar Chart and Performance Table

    The bar chart and performance table below are intended to indicate some of
    the risks of investing in the series by showing changes in the series'
    performance over time. The performance table also shows how the series
    performance over time compares with that of one or more broad measures of
    market performance. The chart and table provide past performance
    information. The series' past performance does not necessarily indicate how
    the series will perform in the future. The returns shown do not reflect fees
    and charges imposed under the variable annuity and life insurance contracts
    through which an investment may be made. If these fees and charges were
    included, they would reduce these returns.


    Bar Chart

    The bar chart shows changes in the annual total returns of the series'
    shares for each calendar year since they were first offered, assuming the
    reinvestment of distributions.

[START BAR GRAPH]

<TABLE>
<S>                <C>                 <C>
24.46%             29.78%              22.32%
 1996               1997                1998
</TABLE>

[END BAR GRAPH]

    During the period shown in the bar chart, the highest quarterly return was
    18.29% (for the calendar quarter ended December 31, 1998) and the lowest
    quarterly return was (10.95)% (for the calendar quarter ended September 30,
    1998).


    Performance Table

    This table shows how the average annual total returns of the series' shares
    compares to a broad measure of market performance and assumes the
    reinvestment of distributions.


    Average Annual Total Returns as of December 31, 1998
    .........................................................................

<TABLE>
<CAPTION>
                                                         1 Year             Life
   <S>                                                    <C>               <C>
   Growth With Income Series*                             22.32%            25.98%
   Standard & Poor's 500 Composite Index **++             28.58%            28.16%
</TABLE>

   ---------

   *   "Life" refers to the period from the commencement of the series'
       investment operations on October 9, 1995, through December 31, 1998.

   ++  Source: CDA/Wiesenberger. "Life" refers to the period from November 1,
       1995, through December 31, 1998.

   **  The Standard & Poor's 500 Composite Index is a broad based, unmanaged
       index of common stock total return performance.

                                       3
<PAGE>

(>) Portfolio Manager

    John D. Laupheimer, a Senior Vice President of the Adviser, has been
    employed by the Adviser as a portfolio manager since 1981. Mr. Laupheimer
    has been the series' portfolio manager since its inception. Mitchell D.
    Dynan, a Senior Vice President of the Adviser, has been employed as a
    portfolio manager since 1986. Mr. Dynan has been the series' portfolio
    manager since May 1, 1999.


                                       4
<PAGE>

    2: Total Return Series
    ..........................................................................

(>) Investment Objectives

    The series' investment objective is primarily to provide above-average
    income (compared to a portfolio invested entirely in equity securities)
    consistent with the prudent employment of capital. Its secondary objective
    is to provide reasonable opportunity for growth of capital and income. The
    series' objectives may be changed without shareholder approval.


(>) Principal Investment Policies

    The series is a "balanced fund," and invests in a combination of equity and
    fixed income securities. Under normal market conditions, the series invests:

    o at least 40%, but not more than 75%, of its net assets in common stocks
      and related securities (referred to as equity securities), such as
      preferred stock; bonds, warrants or rights convertible into stock; and
      depositary receipts for those securities, and

    o at least 25% of its net assets in non-convertible fixed income securities.

    The series may vary the percentage of its assets invested in any one type of
    security (within the limits described above) in accordance with MFS's
    interpretation of economic and money market conditions, fiscal and monetary
    policy and underlying security values.

    Equity Investments. While the series may invest in all types of equity
    securities, MFS generally seeks to purchase for the series equity
    securities, such as common stocks, preferred stocks, convertible securities
    and depositary receipts, of companies that MFS believes are undervalued in
    the market relative to their long-term potential. The equity securities of
    these companies may be undervalued because:

    o they are viewed by MFS as being temporarily out of favor in the market due
      to

        > a decline in the market,

        > poor economic conditions,

        > developments that have affected or may affect the issuer of the
          securities or the issuer's industry, or

    o the market has overlooked them.

    Undervalued equity securities generally have low price-to-book,
    price-to-sales and/or price-to-earnings ratios. The series focuses on
    undervalued equity securities issued by companies with relatively large
    market capitalizations (i.e., market capitalizations of $5 billion or more).

    As noted above, the series' investments in equity securities include
    convertible securities. A convertible security is a security that may be
    converted within a specified period of time into a certain amount of common
    stock of the same or a different issuer. A convertible security generally
    provides:

    o a fixed income stream, and

    o the opportunity, through its conversion feature, to participate in an
      increase in the market price of the underlying common stock.

    MFS uses a bottom-up, as opposed to a top-down, investment style in managing
    the equity-oriented funds (including the equity portion of the series) it
    advises. This means that securities are selected based upon fundamental
    analysis performed by the series' portfolio manager and MFS' large group of
    equity research analysts.

    Fixed Income Investments. The series invests in securities which pay a fixed
    interest rate, which include:

    o U.S. government securities, which are bonds or other debt obligations
      issued by, or whose principal and interest payments are guaranteed or
      supported by, the U.S. government or one of its agencies or
      instrumentalities,

    o mortgage-backed and asset-backed securities, which represent interests in
      a pool of assets such as mortgage loans, car loan receivables, or credit
      card receivables. These investments entitle the series to a share of the
      principal and interest payments made on the underlying mortgage, car loan,
      or credit card. For example, if the series invests in a pool that includes
      your mortgage loan, a share of the principal and interest payments on your
      mortgage would pass to the series, and

    o corporate bonds, which are bonds or other debt obligations issued by
      corporations or other similar entities.

    In selecting fixed income investments for the series, MFS considers the
    views of its large group of fixed income portfolio managers and research
    analysts. This group periodically assesses the three-month total return
    outlook for various segments of the fixed income markets.


                                       5
<PAGE>

    This three-month "horizon" outlook is used by the portfolio manager(s) of
    MFS' fixed-income oriented series (including the fixed-income portion of the
    series) as a tool in making or adjusting a series' asset allocations to
    various segments of the fixed income markets. In assessing the credit
    quality of fixed-income securities, MFS does not rely solely on the credit
    ratings assigned by credit rating agencies, but rather performs its own
    independent credit analysis.


(>) Principal Risks

    The principal risks of investing in the series and the circumstances
    reasonably likely to cause the value of your investment in the series to
    decline are described below. As with any non-money market mutual fund, the
    share price of the series will change daily based on market conditions and
    other factors. Please note that there are many circumstances which could
    cause the value of your investment in the series to decline, and which could
    prevent the series from achieving its objective, that are not described
    here.

    The principal risks of investing in the series are:

    o Allocation Risk: The series will allocate its investments between equity
      and fixed income securities, and among various segments of the fixed
      income markets, based upon judgments made by MFS. The series could miss
      attractive investment opportunities by underweighting markets where there
      are significant returns, and could lose value by overweighting markets
      where there are significant declines.

    o Market Risk: This is the risk that the price of a security held by the
      series will fall due to changing economic, political or market conditions
      or disappointing earnings results.

    o Undervalued Securities Risk: Prices of securities react to the economic
      condition of the company that issued the security. The series' equity
      investments in an issuer may rise and fall based on the issuer's actual
      and anticipated earnings, changes in management and the potential for
      takeovers and acquisitions. MFS will invest in securities that are
      undervalued based on its belief that the market value of these securities
      will rise due to anticipated events and investor perceptions. If these
      events do not occur or are delayed, or if investor perceptions about the
      securities do not improve, the market price of these securities may not
      rise or may fall.

    o Interest Rate Risk: When interest rates rise, the prices of fixed income
      securities in the series' portfolio will generally fall. Conversely, when
      interest rates fall, the prices of fixed income securities in the series'
      portfolio will generally rise.

    o Convertible Securities Risk: Convertible securities, like fixed income
      securities, tend to increase in value when interest rates decline and
      decrease in value when interest rates rise. The market value of a
      convertible security also tends to increase as the market value of the
      underlying stock rises and decrease as the market value of the underlying
      stock declines.

    o Maturity Risk: Interest rate risk will generally affect the price of a
      fixed income security more if the security has a longer maturity. Fixed
      income securities with longer maturities will therefore be more volatile
      than other fixed income securities with shorter maturities. Conversely,
      fixed income securities with shorter maturities will be less volatile but
      generally provide lower returns than fixed income securities with longer
      maturities. The average maturity of the series' fixed income investments
      will affect the volatility of the series' share price.

    o Credit Risk: Credit risk is the risk that the issuer of a fixed income
      security will not be able to pay principal and interest when due. Rating
      agencies assign credit ratings to certain fixed income securities to
      indicate their credit risk. The price of a fixed income security will
      generally fall if the issuer defaults on its obligation to pay principal
      or interest, the rating agencies downgrade the issuer's credit rating or
      other news affects the market's perception of the issuer's credit risk.

    o Liquidity Risk: The fixed income securities purchased by the series may be
      traded in the over-the-counter market rather than on an organized exchange
      and are subject to liquidity risk. This means that they may be harder to
      purchase or sell at a fair price. The inability to purchase or sell these
      fixed income securities at a fair price could have a negative impact on
      the series' performance.

    o Mortgage and Asset-Backed Securities:

        > Maturity Risk:

          [dagger] Mortgage-Backed Securities: A mortgage-backed security will
                   mature when all the mortgages in the pool mature or are
                   prepaid. Therefore, mortgage-backed securities do not have a
                   fixed maturity, and their expected maturities may vary when
                   interest rates rise or fall.

                   + When interest rates fall, homeowners are more likely to
                     prepay their mortgage loans. An increased rate of
                     prepayments on the series' mortgage-backed securities will
                     result in an unforeseen loss of interest income to the
                     series as the series may be required to reinvest assets at
                     a lower interest rate. Because prepayments increase when
                     interest rates fall, the prices of mortgage-backed
                     securities does not increase as much as other fixed income
                     securities when interest rates fall.


                                       6
<PAGE>

                   + When interest rates rise, homeowners are less likely to
                     prepay their mortgage loans. A decreased rate of
                     prepayments lengthens the expected maturity of a
                     mortgage-backed security. Therefore, the prices of
                     mortgage-backed securities may decrease more than prices of
                     other fixed income securities when interest rates rise.

          [dagger] Collateralized Mortgage Obligations: The series may invest in
                   mortgage-backed securities called collateralized mortgage
                   obligations (CMOs). CMOs are issued in separate classes with
                   different stated maturities. As the mortgage pool experiences
                   prepayments, the pool pays off investors in classes with
                   shorter maturities first. By investing in CMOs, the series
                   may manage the prepayment risk of mortgage-backed securities.
                   However, prepayments may cause the actual maturity of a CMO
                   to be substantially shorter than its stated maturity.

          [dagger] Asset-Backed Securities: Asset-backed securities have
                   prepayment risks similar to mortgage-backed securities.

        > Credit Risk: As with any fixed income security, mortgage-backed and
          asset-backed securities are subject to the risk that the issuer will
          default on principal and interest payments. It may be difficult to
          enforce rights against the assets underlying mortgage-backed and
          asset-backed securities in the case of default. The U.S. government or
          its agencies may guarantee the payment of principal and interest on
          some mortgage-backed securities. Mortgage-backed securities and
          asset-backed securities issued by private lending institutions or
          other financial intermediaries may be supported by insurance or other
          forms of guarantees.

    o As with any mutual fund, you could lose money on your investment in the
      series.

    An investment in the series is not a bank deposit and is not insured or
    guaranteed by the Federal Deposit Insurance Corporation or any other
    government agency.


(>) Bar Chart and Performance Table

    The bar chart and performance table below are intended to indicate some of
    the risks of investing in the series by showing changes in the series'
    performance over time. The performance table also shows how the series
    performance over time compares with that of one or more broad measures of
    market performance. The chart and table provide past performance
    information. The series' past performance does not necessarily indicate how
    the series will perform in the future. The returns shown do not reflect fees
    and charges imposed under the variable annuity and life insurance contracts
    through which an investment may be made. If these fees and charges were
    included, they would reduce these returns.


    Bar Chart

    The bar chart shows changes in the annual total returns of the series'
    shares for each calendar year since they were first offered, assuming the
    reinvestment of distributions.

[START BAR CHART]

<TABLE>
<S>                    <C>                     <C>
14.37%                 21.30%                  12.33%
 1996                   1997                    1998
</TABLE>

[END BAR CHART]

    During the period shown in the bar chart, the highest quarterly return was
    9.86% (for the calendar quarter ended June 30, 1997) and the lowest
    quarterly return was (4.28)% (for the calendar quarter ended September 30,
    1998).

                                       7
<PAGE>

    Performance Table

    This table shows how the average annual total returns of the series' shares
    compares to a broad measure of market performance and various other market
    indicators and assumes the reinvestment of distributions.


    Average Annual Total Returns as of December 31, 1998
    .........................................................................

<TABLE>
<CAPTION>
                                                                   1 Year              Life
   <S>                                                             <C>                <C>
   Total Return Series*                                            +12.33%            +18.73%
   S&P 500 Composite Index**+                                      +28.58%            +30.41%
   Lehman Brothers Government/Corporate Bond Index**++             + 9.49%            + 8.58%
   Average balanced fund#                                          +13.48%            +17.64%
</TABLE>

   ---------

   *   "Life" refers to the period from the commencement of the series'
       investment operations, January 3, 1995, through December 31, 1998.

   **  Source: CDA/Wiesenberger. "Life" refers to the period from February 1,
       1995, through December 31, 1998.

   #   Source: Lipper Analytical Services, Inc. "Life" refers to the period from
       February 1, 1995, through December 31, 1998.

   +   The Standard & Poor's 500 Composite Index is a broad based, unmanaged
       index of common stock total return performance.

   ++  The Lehman Brothers Government/Corporate Bond Index is a broad based,
       unmanaged, market-value-weighted index of U.S. Treasury and
       government-agency securities (excluding mortgage-backed securities) and
       investment-grade domestic corporate debt.


(>) Portfolio Manager

    David M. Calabro, a Senior Vice President of MFS, has been employed by the
    Adviser as a portfolio manager since 1992. Mr. Calabro is the head of the
    series' 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. Constantinos
    G. Mokas, a Vice President of MFS, has been a portfolio manager of the
    series since April 1, 1998, and has been employed by the Adviser as a
    portfolio manager since 1990. Mr. Mokas is the manager of the series'
    convertible securities. Lisa B. Nurme, a Senior Vice President of MFS, has
    been a portfolio manager of the series since July 19, 1995, and 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. Kenneth J.
    Enright, a Vice President of MFS, has been employed by the Adviser as a
    portfolio manager since 1986 and has been a portfolio manager of the series
    since January 15, 1999. Mr. Enright is a manager of the common stock portion
    of the series' portfolio.


                                       8
<PAGE>
- -------------------------------------------
III CERTAIN INVESTMENT STRATEGIES AND RISKS
- -------------------------------------------

    Each series may depart from its principal investment strategies by
    temporarily investing for defensive purposes when adverse market, economic
    or political conditions exist. While a series invests defensively, it may
    not be able to pursue its investment objective. A series defensive
    investment policy may not be effective in protecting its value.

    Each series may engage in active and frequent trading to achieve its
    principal investment strategies. This may result in the realization and
    distribution to shareholders of higher capital gains. Frequent trading also
    increases transaction costs, which could detract from the series'
    performance.

    Each series may invest in various types of securities and engage in various
    investment techniques and practices which are not the principal focus of the
    series and therefore are not described in this Prospectus. The types of
    securities and investment techniques and practices in which a series may
    engage, including the principal investment techniques and practices
    described above, are identified in Appendix A to this Prospectus, and are
    discussed, together with their risks, in the trust's Statement of Additional
    Information (referred to as the SAI), which you may obtain by contacting MFS
    Service Center, Inc. (see back cover for address and phone number).

- ---------------------------
IV MANAGEMENT OF THE SERIES
- ---------------------------

(>) Investment Adviser

    Massachusetts Financial Services Company (referred to as MFS or the adviser)
    is the investment adviser to each series. 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,
    Massachusetts Investors Trust. Net assets under the management of the MFS
    organization were approximately $102.9 billion on behalf of approximately
    3.8 million investor accounts as of January 31, 1999. As of such date, the
    MFS organization managed approximately $73.6 billion of net assets in equity
    fund and equity portfolios. Approximately $4.7 billion of the assets managed
    by MFS are invested in securities of foreign issuers and foreign denominated
    securities of U.S. issuers. MFS is located at 500 Boylston Street, Boston,
    Massachusetts 02116.

    MFS provides investment management and related administrative services and
    facilities to each series, including portfolio management and trade
    execution. For these services each series pays MFS an annual management fee
    as set forth in the Expense Summary.

    MFS or its affiliates generally pay an administrative service fee to
    insurance companies which use the series as underlying investment vehicles
    for their variable annuity and variable life insurance contracts based upon
    the aggregate net assets of the series attributable to these contracts.
    These fees are not paid by the series, their shareholders, or by the
    contract holders.


(>) Administrator

    MFS provides each series with certain financial, legal, compliance,
    shareholder communications and other administrative services. MFS is
    reimbursed by each series for a portion of the costs it incurs in providing
    these services.


(>) Distributor

    MFS Fund Distributors, Inc. (referred to as MFD), a wholly owned subsidiary
    of MFS, is the distributor of shares of the series.


(>) Shareholder Servicing Agent

    MFS Service Center, Inc. (referred to as MFSC), a wholly owned subsidiary of
    MFS, performs transfer agency and certain other services for each series,
    for which it receives compensation from each series.


- -----------------------
V DESCRIPTION OF SHARES
- -----------------------

    The trust offers shares of each of its series to separate accounts
    established by insurance companies in order to serve as investment vehicles
    for variable annuity and variable life insurance contracts. The trust also
    offers shares of each of its series to qualified pension and retirement
    plans. All purchases, redemptions and exchanges of shares are made through
    these insurance company separate accounts and plans, which


                                       9
<PAGE>

    are the record owner of the shares. Contract holders and plan beneficiaries
    seeking to purchase, redeem or exchange interests in the trust's shares
    should consult with the insurance company which issued their contracts or
    their plan sponsor.


- --------------------
VI OTHER INFORMATION
- --------------------


(>) Pricing of Series' Shares

    The price of each series' shares is based on its net asset value. The net
    asset value of each series' shares is determined at the close of regular
    trading each day that the New York Stock Exchange is open for trading
    (generally, 4:00 p.m., Eastern time) (referred to as the valuation time). To
    determine net asset value, each series values its assets at current market
    values, or at fair value as determined by the Adviser under the direction of
    the Board of Trustees that oversees the series if current market values are
    unavailable. Fair value pricing may be used by a series when current market
    values are unavailable or when an event occurs after the close of the
    exchange on which the series' portfolio securities are principally traded
    that is likely to have changed the value of the securities. The use of fair
    value pricing by a series may cause the net asset value of its shares to
    differ significantly from the net asset value that would be calculated using
    current market values.

    Insurance companies and plan sponsors are the designees of the trust for
    receipt of purchase, exchange and redemption orders from contractholders and
    plan beneficiaries. An order submitted to the trust's designee by the
    valuation time will receive the net asset value next calculated; provided
    that the trust receives notice of the order generally by 9:30 a.m. eastern
    time on the next day on which the New York Stock Exchange is open for
    trading.

    Certain series invest in securities which are primarily listed on foreign
    exchanges that trade on weekends and other days when the series does not
    price its shares. Therefore, the value of these series' shares may change on
    days when you will not be able to purchase or redeem their shares.


(>) Distributions

    Each series intends to pay substantially all of its net income (including
    net short-term capital gain) to shareholders as dividends at least annually.
    Any realized net capital gains are also distributed at least annually.


(>) Tax Considerations

    Each series of the trust is treated as a separate entity for federal income
    tax purposes. As long as a series qualifies for treatment as a regulated
    investment company (which it has in the past and intends to do so in the
    future), it pays no federal income tax on the earnings it distributes to
    shareholders. In addition, each series also intends to continue to diversify
    its assets to satisfy the federal diversification tax rules applicable to
    separate accounts that fund variable insurance and annuity contracts.

    Shares of the series are offered to insurance company separate accounts and
    qualified pension and retirement plan sponsors. Consult with the insurance
    company which issued your contract or your plan sponsor or financial advisor
    to understand the federal tax treatment of your investment.


(>) Right to Reject Purchase and Exchange Orders

    Purchases and exchanges should be made for investment purposes only. Each
    series reserves the right to reject or restrict any specific purchase or
    exchange request. Because an exchange request involves both a request to
    redeem shares of one series and to purchase shares of another series, the
    series consider the underlying redemption and purchase requests conditioned
    upon the acceptance of each of these underlying requests. Therefore, in the
    event that the series reject an exchange request, neither the redemption nor
    the purchase side of the exchange will be processed.


(>) Market Timing Policies

    The series are not designed for professional market timing organizations or
    other entities using programmed or frequent exchanges. The series define a
    "market timer" as an individual, or organization acting on behalf of one or
    more individuals, if the individual or organization makes during the
    calendar year six or more exchange requests among the series.

    Accounts under common ownership or control, including accounts administered
    by market timers, will be aggregated for purposes of this definition.


                                       10
<PAGE>

    The series may impose specific limitations on market timers, including:

    o delaying for up to seven days the purchase side of an exchange request by
      market timers;

    o rejecting or otherwise restricting purchase or exchange requests by market
      timers; and

    o permitting exchanges by market timers only into certain series.


(>) In-kind distributions

    The series have reserved the right to pay redemption proceeds by a
    distribution in-kind of portfolio securities (rather than cash). In the
    event that the series makes an in-kind distribution, you could incur the
    brokerage and transaction charges when converting the securities to cash.
    The series do not expect to make in-kind distributions.


(>) Unique Nature of Series

    MFS may serve as the investment adviser to other funds which have similar
    investment goals and principal investment policies and risks to the series,
    and which may be managed by the series' portfolio manager(s). While a series
    may have many similarities to these other funds, its investment performance
    will differ from their investment performance. This is due to a number of
    differences between a series and these similar products, including
    differences in sales charges, expense ratios and cash flows.


(>) Year 2000 Readiness Disclosure

    The series could be adversely affected if the computer systems used by MFS,
    the series' other service providers or the companies in which the series
    invests do not properly process date-related information from and after
    January 1, 2000 (the "Year 2000 Issue"). MFS recognizes the importance of
    the Year 2000 Issue and, to address Year 2000 compliance, created a
    separately funded Year 2000 Program Management Office in 1996 comprised of a
    specialized staff reporting directly to MFS senior management. The Office,
    with the help of external consultants, is responsible for overall
    coordination, strategy formulation, communications and issue resolution with
    respect to Year 2000 issues. While MFS systems will be tested for Year 2000
    readiness before the turn of the century, there are significant systems
    interdependencies in the domestic and foreign markets for securities, the
    business environments in which companies held by the series operate and in
    MFS' own business environment. MFS has been working with the series' other
    service providers to identify and respond to potential problems with respect
    to Year 2000 readiness and to develop contingency plans. Year 2000 readiness
    is also one of the factors considered by MFS in its ongoing assessment of
    companies in which the series invests. There can be no assurance, however,
    that these steps will be sufficient to avoid any adverse impact on the
    series.


(>) Potential Conflicts

    Shares of the series are offered to the separate accounts of insurance
    companies that may be affiliated or unaffiliated with MFS and each other
    ("shared funding") and 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 board of
    trustees which oversees the series intends 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. If such a
    conflict were to occur, one or more separate accounts of the insurance
    companies might be required to withdraw its investments in one or more
    series. This might force a series to sell securities at disadvantageous
    prices.


- ------------------------
VII FINANCIAL HIGHLIGHTS
- ------------------------

    The financial highlights table is intended to help you understand the
    series' financial performance for the past 5 years, or, if a series has not
    been in operation that long, since the time it commenced investment
    operations. Certain information reflects financial results for a single
    series' share. The total returns in the table represent the rate by which an
    investor would have earned (or lost) on an investment in a series (assuming
    reinvestment of all distributions). This information has been audited by the
    trust's independent auditors, whose report, together with the trust's
    financial statements, are included in the trust's Annual Report to
    shareholders. The series' Annual Report is available upon request by
    contacting MFSC (see back cover for address and telephone number). These
    financial statements are incorporated by reference into the SAI. The trust's
    independent auditors are Deloitte & Touche LLP.


                                       11
<PAGE>

    1. Growth With Income Series
    .........................................................................

<TABLE>
<CAPTION>
                                                                                                   Period Ended
                                                                   Year Ended December 31,        December 31,
                                                                 1998        1997        1996        1995*
   ------------------------------------------------------------------------------------------------------------
   <S>                                                         <C>          <C>          <C>          <C>
   Per share data (for a share outstanding throughout
    each period):
   Net asset value -- beginning of period ...................  $  16.44     $  12.98     $10.61       $10.00
                                                               --------     --------     ------       ------
   Income from investment operations# --
    Net investment income[sec] ..............................  $   0.13     $   0.16     $ 0.18       $ 0.05
    Net realized and unrealized gain on investments and
     foreign currency .......................................      3.54        3.70        2.42         0.61
                                                               --------     --------     ------       ------
      Total from investment operations ......................  $   3.67     $   3.86     $ 2.60       $ 0.66
                                                               --------     --------     ------       ------
   Less distributions declared to shareholders --
    From net investment income ..............................  $     --     $ (0.07)     $(0.09)      $(0.05)
    From net realized gain on investments and foreign
     currency transactions ..................................        --       (0.29)      (0.13)          --
    In excess of net realized gain on investments and
     foreign currency transactions ..........................        --       (0.04)      (0.01)          --
                                                               --------     -------      ------       ------
      Total distributions declared to shareholders ..........  $     --     $ (0.40)     $(0.23)      $(0.05)
                                                               --------     -------      ------       ------
   Net asset value -- end of period .........................  $  20.11     $ 16.44      $12.98       $10.61
                                                               --------     -------      ------       ------
   Total return .............................................     22.32%      29.78%      24.46%        6.64%++
   Ratios (to average net assets)/Supplemental data[sec]:
    Expenses## ..............................................      0.95%       1.00%       1.01%        1.00%+
    Net investment income ...................................      0.73%       0.93%       1.52%        2.20%+
   Portfolio turnover .......................................        57%         42%         41%           2%
   Net assets at end of period (000 omitted) ................  $244,310     $58,045      $9,174       $  365
</TABLE>

   ---------

   *   For the period from the commencement of the series' investment
       operations, October 9, 1995, through December 31, 1995.

   +   Annualized.

   ++  Not annualized.

   #   Per share data are based on average shares outstanding.

   ##  The 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. The series' expenses are calculated without reduction for
       this expense offset arrangement.

 [sec] Prior to October 2, 1998, subject to reimbursement by the series, the
       investment adviser voluntarily agreed to maintain the expenses of the
       series, exclusive of management fees, at not more than 0.25% of average
       daily net assets. To the extent actual expenses were over/under this
       limitation, the net investment income (loss) per share and ratios would
       have been:


<TABLE>
    <S>                                        <C>        <C>         <C>           <C>
    Net investment income (loss) ..........    $0.14      $(0.13)     $(0.05)       $(0.41)
    Ratios (to average net assets):
     Expenses## ...........................     0.88%       1.10%       2.07%        21.44%+
     Net investment income (loss) .........     0.80%       0.82%       0.46%       (18.24)%+
</TABLE>


                                       12
<PAGE>

    2. Total Return Series
    .........................................................................

<TABLE>
<CAPTION>
                                                                                                   Period Ended
                                                                    Year Ended December 31,        December 31,
                                                                  1998        1997        1996        1995*
  -------------------------------------------------------------------------------------------------------------
   <S>                                                         <C>          <C>        <C>            <C>
   Per share data (for a share outstanding throughout
    each period):
   Net asset value -- beginning of period ...................  $  16.63     $ 13.71    $  12.25       $10.00
                                                               --------     -------    --------       ------
   Income from investment operations# --
    Net investment income[sec] ..............................  $   0.53     $  0.52    $   0.46       $ 0.41
    Net realized and unrealized gain on investments and
     foreign currency .......................................      1.49        2.40        1.30         2.32
                                                               --------     -------    --------       ------
      Total from investment operations ......................  $   2.02     $  2.92    $   1.76       $ 2.73
                                                               --------     -------    --------       ------
   Less distributions declared to shareholders --
    From net investment income ..............................  $  (0.24)    $    --    $  (0.21)      $(0.25)
    From net realized gain on investments and foreign
     currency transactions ..................................     (0.29)         --       (0.09)       (0.23)
                                                               --------     -------    --------       ------
      Total distributions declared to shareholders ..........  $  (0.53)    $    --    $  (0.30)      $(0.48)
                                                               --------     -------    --------       ------
   Net asset value -- end of period .........................  $  18.12     $ 16.63    $  13.71       $12.25
                                                               --------     -------    --------       ------
   Total return .............................................     12.33%      21.30%      14.37%       27.34%++
   Ratios (to average net assets)/Supplemental data[sec]:
    Expenses## ..............................................      1.00%       1.00%       1.00%        1.00%+
    Net investment income ...................................      3.05%       3.25%       3.59%        3.83%+
   Portfolio turnover .......................................       100%         93%         76%          16%
   Net assets at end of period (000 omitted) ................  $171,182     $75,612     $19,250       $2,797
</TABLE>

   ---------

   *   For the period from the commencement of the series' investment
       operations, January 3, 1995, through December 31, 1995.

   +   Annualized.

   ++  Not annualized.

   #   Per share data are based on average shares outstanding.

   ##  The 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. The series' expenses are
       calculated without reduction for this expense.

 [sec] Subject to reimbursement by the series, the investment adviser
       voluntarily agreed to maintain the expenses of the series, exclusive of
       management fees, at not more than 0.25% of average daily net assets. To
       the extent actual expenses were over/under this limitation, the net
       investment income per share and the ratios would have been:

<TABLE>
    <S>                                 <C>        <C>        <C>        <C>
    Net investment income ..........    $0.54      $0.52      $0.32      $0.22
    Ratios (to average net assets):
     Expenses## ....................     0.91%      1.02%      2.10%      2.49%+
     Net investment income .........     3.14%      3.23%      2.49%      2.09%+
</TABLE>


                                       13
<PAGE>

<TABLE>
<S>                                                                                <C>
- -------------------                                                                -------------------------------------------------
A p p e n d i x   A                                                                G r o w t h   W i t h   I n c o m e   S e r i e s
- -------------------                                                                -------------------------------------------------
</TABLE>

(>) Investment Techniques and Practices

    In pursuing its investment objectives and investment policies, the Growth
    With Income Series may engage in the following investment techniques and
    practices, which are described, together with their risks, in the SAI.
    Investment techniques and practices which are the principal focus of the
    series are also described in the Risk Return Summary of the Prospectus.


<TABLE>
<CAPTION>
   Symbols                                      [checkmark] permitted                                              -- not permitted
- -----------------------------------------------------------------------------------------------------------------------------------
  <S>                                                  <C>                <S>                                            <C>
  Debt Securities                                                         Investment in Other Investment Companies
   Asset-Backed Securities                                                 Open-End                                      [checkmark]
    Collateralized Mortgage Obligations and Multiclass                     Closed-End                                    [checkmark]
      Pass-Through Securities                                   --        Lending of Portfolio Securities                [checkmark]
    Corporate Asset-Backed Securities                           --        Leveraging Transactions
    Mortgage Pass-Through Securities                            --         Bank Borrowings                                       --*
    Stripped Mortgage-Backed Securities                         --         Mortgage "Dollar-Roll" Transactions                   --*
   Corporate Securities                                [checkmark]        Reverse Repurchase Agreements                          --*
   Loans and Other Direct Indebtedness                          --        Options
   Lower Rated Bonds                                            --         Options on Foreign Currencies                 [checkmark]
   Municipal Bonds                                              --         Options on Futures Contracts                  [checkmark]
   Speculative Bonds                                            --         Options on Securities                         [checkmark]
   U.S. Government Securities                                   --         Options on Stock Indices                      [checkmark]
   Variable and Floating Rate Obligations              [checkmark]         Reset Options                                          --
   Zero Coupon Bonds, Deferred Interest Bonds and PIK                      "Yield Curve" Options                                  --
    Bonds                                              [checkmark]        Repurchase Agreements                          [checkmark]
  Equity Securities                                    [checkmark]        Restricted Securities                          [checkmark]
  Foreign Securities Exposure                                             Short Sales                                             --
   Brady Bonds                                                  --        Short Sales Against the Box                    [checkmark]
   Depositary Receipts                                 [checkmark]        Short Term Instruments                         [checkmark]
   Dollar-Denominated Foreign Debt Securities                   --        Swaps and Related Derivative Instruments                --
   Emerging Markets                                    [checkmark]        Temporary Borrowings                           [checkmark]
   Foreign Securities                                  [checkmark]        Temporary Defensive Positions                  [checkmark]
  Forward Contracts                                    [checkmark]        Warrants                                       [checkmark]
  Futures Contracts                                    [checkmark]        "When-Issued" Securities                       [checkmark]
  Indexed Securities/Structured Products                        --
  Inverse Floating Rate Obligations                             --
</TABLE>

     *May be changed only with shareholder approval.

                                      A-1
<PAGE>

<TABLE>
<S>                                                                                           <C>
- -------------------                                                                           --------------------------------------
A p p e n d i x   A                                                                            T o t a l   R e t u r n   S e r i e s
- -------------------                                                                           --------------------------------------
</TABLE>

(>) Investment Techniques and Practices

    In pursuing its investment objectives and investment policies, the Total
    Return Series may engage in the following investment techniques and prac
    tices, which are described, together with their risks, in the SAI.
    Investment techniques and practices which are the principal focus of the
    series are also described in the Risk Return Summary of the Prospectus.

<TABLE>
<CAPTION>
   Symbols                                         [checkmark] permitted                                          -- not permitted
- ----------------------------------------------------------------------------------------------------------------------------------
  <S>                                                  <C>                <S>                                            <C>
  Debt Securities                                                         Investment in Other Investment Companies
   Asset-Backed Securities                                                  Open-End Funds                               [checkmark]
    Collateralized Mortgage Obligations and Multiclass                      Closed-End Funds                             [checkmark]
      Pass-Through Securities                          [checkmark]        Lending of Portfolio Securities                [checkmark]
    Corporate Asset-Backed Securities                  [checkmark]        Leveraging Transactions
    Mortgage Pass-Through Securities                   [checkmark]         Bank Borrowings                                       --*
    Stripped Mortgage-Backed Securities                [checkmark]         Mortgage "Dollar-Roll" Transactions                     *
   Corporate Securities                                [checkmark]         Reverse Repurchase Agreements                           *
   Loans and Other Direct Indebtedness                 [checkmark]        Options
   Lower Rated Bonds                                   [checkmark]         Options on Foreign Currencies                 [checkmark]
   Municipal Bonds                                     [checkmark]         Options on Futures Contracts                  [checkmark]
   Speculative Bonds                                   [checkmark]         Options on Securities                         [checkmark]
   U.S. Government Securities                          [checkmark]         Options on Stock Indices                      [checkmark]
   Variable and Floating Rate Obligations              [checkmark]         Reset Options                                 [checkmark]
   Zero Coupon Bonds, Deferred Interest Bonds and PIK                      "Yield Curve" Options                         [checkmark]
    Bonds                                              [checkmark]        Repurchase Agreements                          [checkmark]
  Equity Securities                                    [checkmark]        Restricted Securities                          [checkmark]
  Foreign Securities Exposure                                             Short Sales                                             --
   Brady Bonds                                         [checkmark]        Short Sales Against the Box                             --
   Depositary Receipts                                 [checkmark]        Short Term Instruments                         [checkmark]
   Dollar-Denominated Foreign Debt Securities          [checkmark]        Swaps and Related Derivative Instruments       [checkmark]
   Emerging Markets                                    [checkmark]        Temporary Borrowings                           [checkmark]
   Foreign Securities                                  [checkmark]        Temporary Defensive Positions                  [checkmark]
  Forward Contracts                                    [checkmark]        Warrants                                       [checkmark]
  Futures Contracts                                    [checkmark]        "When-Issued" Securities                       [checkmark]
  Indexed Securities/Structured Products               [checkmark]
  Inverse Floating Rate Obligations                    [checkmark]
</TABLE>

     *May be changed only with shareholder approval.

                                      A-2
<PAGE>

    MFS[RegTM] VARIABLE INSURANCE TRUST SM

    If you want more information about the trust and its series, the following
    documents are available free upon request:

    Annual/Semiannual Reports. These reports contain information about the
    series' actual investments. Annual reports discuss the effect of recent
    market conditions and the series' investment strategy on the series'
    performance during its last fiscal year.

    Statement of Additional Information (SAI). The SAI, dated May 1, 1999,
    provides more detailed information about the trust and its series and is
    incorporated into this prospectus by reference.

    You can get free copies of the annual/semiannual reports, the SAI and other
    information about the trust and its series, and make inquiries about the
    trust and its series, by contacting:

      MFS Service Center, Inc.
      2 Avenue de Lafayette
      Boston, MA 02111-1738
      Telephone: 1-800-343-2829, ext. 3500
      Internet: http://www.mfs.com

    Information about the trust and its series (including its prospectus, SAI
    and shareholder reports) can be reviewed and copied at the:

      Public Reference Room
      Securities and Exchange Commission
      Washington, D.C., 20549-6009

    Information on the operation of the Public Reference Room may be obtained by
    calling the Commission at 1-800-SEC-0330. Reports and other information
    about the trust and its series are available on the Commission's Internet
    website at http://www.sec.gov, and copies of this information may be
    obtained, upon payment of a duplicating fee, by writing the Public Reference
    Section at the above address.


    The trust's Investment Company Act file number is 811-8326






                                                   MSG 11/98 224M 90/290/390/890


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