MFS VARIABLE INSURANCE TRUST
497, 1999-05-04
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[Logo: MFS(RegTM)
       INVESTMENT MANAGEMENT
       75 YEARS
       WE INVENTED THE MUTUAL FUND(RegTM)]

- ----------------------------------------
MFS[RegTM] VARIABLE INSURANCE TRUST (SM)
- ----------------------------------------

MAY 1, 1999

                                                                     Prospectus

MFS[RegTM] EMERGING GROWTH SERIES
MFS[RegTM] TOTAL RETURN SERIES
MFS[RegTM] UTILITIES SERIES
- --------------------------------------------------------------------------------
This Prospectus describes three of the series of the MFS Variable Insurance
Trust (referred to as the trust):

1. MFS Emerging Growth Series seeks to provide long-term growth of capital
   (referred to as the Emerging Growth Series);

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); and

3. MFS Utilities Series seeks capital growth and current income (income above
   that available from a portfolio invested entirely in equity securities)
   (referred to as the Utilities 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>
<S>   <C>                                                            <C>
                                                                     Page
I     Expense Summary ............................................     1
II    Risk Return Summary ........................................     2
      1. Emerging Growth Series ..................................     2
      2. Total Return Series .....................................     4
      3. Utilities Series ........................................     8
III   Certain Investment Strategies and Risks ....................    13
IV    Management of the Series ...................................    13
V     Description of Shares ......................................    13
VI    Other Information ..........................................    14
VII   Financial Highlights .......................................    15
      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). Three 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>
                                                          Emerging       Total
                                                           Growth       Return      Utilities
                                                           Series       Series       Series
                                                         ----------   ----------   ----------
   <S>                                                       <C>          <C>          <C>
   Management Fee ....................................       0.75%        0.75%        0.75%
   Other Expenses(1) .................................       0.10%        0.16%        0.26%
                                                             ----         ----         ----
   Total Annual Series Operating Expenses(1) .........       0.85%        0.91%        1.01%
</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.

>  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>
   Emerging Growth Series        $ 87      $271      $471     $1,049
   Total Return Series             93       290       504      1,120
   Utilities Series               103       322       558      1,236
</TABLE>

                                       1
<PAGE>

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

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

    1: Emerging Growth Series
    ............................................................................

>   Investment Objective

    The series' investment objective is long term growth of capital. 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,
    of emerging growth companies. Emerging growth companies are companies which
    MFS believes are either:

    o early in their life cycle but which have the potential to become major
      enterprises, or

    o major enterprises whose rates of earnings growth are expected to
      accelerate because of special factors, such as rejuvenated management, new
      products, changes in consumer demand, or basic changes in the economic
      environment.

    Emerging growth companies may be of any size, and MFS would expect these
    companies to have products, technologies, management, markets and
    opportunities which will facilitate earnings growth over time that is well
    above the growth rate of the overall economy and the rate of inflation. The
    series' investments may include securities listed on a securities exchange
    or traded in the over-the-counter markets.

    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.

>   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 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 Emerging Growth 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. Investments in emerging growth companies may be subject to
      more abrupt or erratic market movements and may involve greater risks than
      investments in other companies. Emerging growth companies often:

      >   have limited product lines, markets and financial resources

      >   are dependent on management by one or a few key individuals

      >   have shares which suffer steeper than average price declines after
          disappointing earnings reports and are more difficult to sell at
          satisfactory prices

    o Over-the-Counter Risk: Over-the-counter (OTC) transactions involve risks
      in addition to those associated with transactions in securities traded on
      exchanges. OTC-listed companies may have limited product lines, markets or
      financial resources. Many OTC stocks trade less frequently and in smaller
      volume than exchange-listed stocks. The values of these stocks may be more
      volatile than exchange-listed stocks, and the series may experience
      difficulty in establishing or closing out positions in these stocks at
      prevailing market prices.

    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.

                                       2
<PAGE>

>   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.

    [Begin Bar Chart]

    1996    17.02%
    1997    21.90%
    1998    34.16%

    [End Bar Chart]

    During the period shown in the bar chart, the highest quarterly return was
    27.04% (for the calendar quarter ended December 31, 1998) and the lowest
    quarterly return was (13.11)% (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 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>
    Emerging Growth Series*                                34.16%             +26.55%
    Russell 2000 Total Return Index**+                     -2.55%             +12.03%
    Standard & Poor's 500 Composite Index**++             +28.58%             +28.16%
</TABLE>

    ---------

    *   "Life" refers to the period from the commencement of the series'
        investment operations, July 24, 1995, through December 31, 1998.

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

    +   The Russell 2000 Total Return Index is a broad based, unmanaged index
        comprised of 2,000 of the smallest U.S.-domiciled company common stocks
        (on the basis of capitalization) that are traded in the United States on
        the New York Stock Exchange, the American Stock Exchange, and Nasdaq.

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

>   Portfolio Manager

    John W. Ballen, President of MFS, has been employed by the Adviser as a
    portfolio manager since 1984. Mr. Ballen has been the series'  portfolio
    manager since its inception. Toni Y. Shimura, a Vice President of MFS, has
    been employed by the Adviser as a portfolio manager since 1987. Ms. Shimura
    became portfolio manager of the series on November 30, 1995.

                                       3
<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.

                                       4
<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.


                                     5
<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.

        [Begin Bar Chart]

        1996     14.37%
        1997     21.30%
        1998     12.33%

        [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).

                                       6
<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.

                                       7
<PAGE>

    3: Utilities Series
    ............................................................................

>   Investment Objective

    The series' investment objective is to seek capital growth and current
    income (income above that available from a portfolio invested entirely in
    equity securities). 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 equity and debt securities of domestic and foreign companies
    in the utilities industry. MFS considers a company to be in the utilities
    industry if, at the time of investment, MFS determines that a substantial
    portion of the company's assets or revenues are derived from one or more
    utilities. Securities in which the series invests are not selected based
    upon what sector of the utilities industry a company is in (i.e., electric,
    gas, telecommunications) or upon a company's geographic region. Companies in
    the utilities industry include:

    o 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

    o companies engaged in telecommunications, including telephone, cellular
      telephone, telegraph, satellite, microwave, cable television and other
      communications media (but not companies engaged in public broadcasting).

    The series is a non-diversified mutual fund. This means that the series may
    invest a relatively high percentage of its assets in one or a few issuers.

    Equity Investments. 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. In performing this
    analysis and selecting securities for the series, MFS places particular
    emphasis on each of the following factors:

    o the current regulatory environment;

    o the strength of the company's management team; and

    o the company's growth prospects and valuation relative to its long-term
      potential.

    Equity securities purchased by the series consist of common stocks,
    preferred stocks, convertible securities and depositary receipts. Equity
    securities may be listed on a securities exchange or traded in the
    over-the-counter markets.

    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.

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

    o corporate bonds, which are bonds or other debt obligations issued by
      corporations or similar entities, including lower rated bonds, commonly
      known as junk bonds, which are bonds assigned low credit ratings by credit
      rating agencies or which are unrated and considered by MFS to be
      comparable in quality to lower rated bonds;

    o mortgage-backed securities and asset-backed securities, which are
      securities that 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 invested in a pool that included your mortgage loan, a share of the
      principal and interest payments on your mortgage would pass to the series;
      and

    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.

    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.

                                       8
<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.

    Foreign Securities. The series invests in foreign securities such as:

    o equity securities of foreign companies in the utilities industry,

    o fixed income securities of foreign companies in the utilities industry,
      and

    o fixed income securities issued by foreign governments.

    These investments may expose the series 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 objective, that are not described
    here.

    The principal risks of investing in the series are:

    o Concentration: The series' investment performance will be closely tied to
      the performance of utility companies. 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;

      >   restrictions on operations and increased costs and delays as a result
          of environmental and nuclear safety regulations;

      >   coping with the general effects of energy conservation;

      >   technological innovations which may render existing plants, equipment
          or products obsolete;

      >   the potential impact of natural or man-made disasters;

      >   difficulty obtaining adequate returns on invested capital, even if
          frequent rate increases are approved by public service commissions;

      >   the high cost of obtaining financing during periods of inflation;

      >   difficulties of the capital markets in absorbing utility debt and
          equity securities; and

      >   increased competition.

    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. Because utility
    companies are faced with the same obstacles, issues and regulatory burdens,
    their securities may react similarly and more in unison to these or other
    market conditions. These price movements may have a larger impact on the
    series than on a series with a more broadly diversified portfolio.

    o Regulation: The value of utility company securities may decline because
      governmental regulation controlling the utilities industry can change.
      This regulation may prevent or delay the utility company from passing
      along cost increases to its customers. Furthermore, regulatory authorities
      may not grant future rate increases. Any increases granted may not be
      adequate to permit the payment of dividends on common stocks.

    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.

                                       9
<PAGE>

    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 affect the price of a fixed income
      security more if the security has a longer maturity because changes in
      interest rates are increasingly difficult to predict over longer periods
      of time. 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 Mortgage-Backed and Asset-Backed Securities Risk

        > 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 do not increase as much as other fixed income
                     securities when interest rates fall.

                   + 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 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.

                                       10
<PAGE>

        > 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 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 Non-Diversified Status Risk: Because the series may invest a higher
      percentage of its assets in a small number of issuers, the series is more
      susceptible to any single economic, political or regulatory event
      affecting those issuers than is a diversified fund.

    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.

        [Begin Bar Chart]

        1996   18.51%
        1997   31.70%
        1998   18.06%

        [End Bar Chart]

    During the period shown in the bar chart, the highest quarterly return was
    12.01% (for the calendar quarter ended December 31, 1996) and the lowest
    quarterly return was (3.79)% (for the calendar quarter ended September 30,
    1998).

                                       11
<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 assumes the
    reinvestment of distributions.

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

<TABLE>
<CAPTION>
                                                    1 Year              Life
    <S>                                             <C>                <C>
    Utilities Series*                               18.06%             25.40%
    Standard & Poor's Utility Index+**              14.77%             18.29%
</TABLE>

    ---------

    *  "Life" refers to the period from the commencement of the series'
       investment operations on January 3, 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 Utilities Index is a broad based, unmanaged,
       market-capitalization-weighted, total return index of all utility stocks
       in the Standard & Poor's 500 Composite Index, a broad based index of
       common stock total return peformance.

>   Portfolio Manager

    Maura A. Shaughnessy, a Senior Vice President of the Adviser, has been
    employed by the Adviser as a portfolio manager since 1991. Ms. Shaughnessy
    has been the series' portfolio manager since its inception.

                                       12
<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 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.

                                       13
<PAGE>

- --------------------
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.

                                       14
<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.

                                       15
<PAGE>

   1. Emerging Growth 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 ...................    $ 16.13       $ 13.24       $ 11.41      $  10.00
                                                                 -------       -------       -------      --------
   Income from investment operations# --
    Net investment income (loss)[sec] .......................    $ (0.05)      $ (0.06)      $ (0.01)     $   0.01
    Net realized and unrealized gain on investments and
     foreign currency .......................................       5.55          2.95          1.95          1.74
                                                                 -------       -------       -------      --------
      Total from investment operations ......................    $  5.50       $  2.89       $  1.94      $   1.75
                                                                 -------       -------       -------      --------
   Less distributions declared to shareholders --
    From net investment income ..............................    $    --       $    --       $    --      $  (0.01)
    From net realized gain on investments and foreign
     currency transactions ..................................      (0.05)           --         (0.06)        (0.26)
    In excess of net realized gain on investments and
     foreign currency transactions ..........................      (0.11)           --         (0.05)           --
    From paid-in capital ....................................         --            --            --         (0.07)
                                                                 -------       -------       -------      --------
      Total distributions declared to shareholders ..........    $ (0.16)      $    --       $ (0.11)     $  (0.34)
                                                                 -------       -------       -------      --------
   Net asset value -- end of period .........................    $ 21.47       $ 16.13       $ 13.24      $  11.41
                                                                 -------       -------       -------      --------
   Total return .............................................      34.16%        21.90%        17.02%        17.41%++
   Ratios (to average net assets)/Supplemental data[sec]:
    Expenses## ..............................................       0.85%         0.90%         1.00%         1.00%+
    Net investment income (loss) ............................      (0.29)%       (0.38)%       (0.08)%        0.10%+
   Portfolio turnover .......................................         71%          112%           96%           73%
   Net assets at end of period (000 omitted) ................   $908,987      $384,480      $104,956      $  3,869
</TABLE>

   ---------

   *     For the period from the commencement of the series' investment
         operations, July 24, 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 offset arrangement.

   [sec] Prior to January 1, 1998, the investment adviser voluntarily agreed to
         maintain, subject to reimbursement by the series, the expenses of the
         series at not more than 1.00% of average daily net assets. To the
         extent actual expenses were over or under this limitation, the net
         investment loss per share and the ratios would have been:

<TABLE>
    <S>                                    <C>    <C>        <C>        <C>
    Net investment loss ...........        --     $(0.05)    $(0.03)    $(0.18)
    Ratios (to average net assets):
     Expenses## ...................        --       0.87%      1.16%      2.91%+
     Net investment loss ..........        --      (0.35)%    (0.23)%    (1.78)%+
</TABLE>

                                       16
<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>

                                       17
<PAGE>

   3. Utilities 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 .................   $ 17.99     $ 13.66    $12.57     $10.00
                                                              -------     -------    ------     ------
   Income from investment operations# --
    Net investment income[sec] ............................   $  0.46     $  0.44    $ 0.55     $ 0.39
    Net realized and unrealized gain on investments and
     foreign currency .....................................      2.68        3.89      1.78       3.00
                                                              -------     -------    ------     ------
      Total from investment operations ....................   $  3.14     $  4.33    $ 2.33     $ 3.39
                                                              -------     -------    ------     ------
   Less distributions declared to shareholders --
    From net investment income ............................   $ (0.24)    $    --    $(0.35)    $(0.24)
    From net realized gain on investments and foreign
     currency transactions ................................     (1.07)         --     (0.88)     (0.58)
    In excess of net realized gain on investments and
     foreign currency transactions ........................        --          --     (0.01)        --
                                                              -------     -------    ------     ------
      Total distributions declared to shareholders ........   $ (1.31)    $    --    $(1.24)    $(0.82)
                                                              -------     -------    ------     ------
   Net asset value -- end of period .......................   $ 19.82     $ 17.99    $13.66     $12.57
                                                              -------     -------    ------     ------
   Total return ...........................................     18.06%      31.70%    18.51%     33.94%++
   Ratios (to average net assets)/
    Supplemental data[sec]:
    Expenses## ............................................      1.01%       1.00%     1.00%      1.00%+
    Net investment income .................................      2.48%       2.92%     4.19%      3.66%+
   Portfolio turnover .....................................       133%         69%      121%        94%
   Net assets at end of period (000 omitted) ..............   $81,726     $30,147    $9,572     $2,373
</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. For fiscal years
         ending after September 1, 1995, the series' expenses are calculated
         without reduction for this expense offset arrangement.

   [sec] Subject to reimbursement by the series, the investment adviser agreed
         to maintain 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 ..........  $0.47     $0.41     $0.32      $0.17
   Ratios (to average net assets):
    Expenses## ....................   0.98%     1.20%     2.75%      3.08%+
    Net investment income .........   2.51%     2.71%     2.44%      1.62%+
</TABLE>

                                       18
<PAGE>

- -------------------                 -------------------------------------------
A p p e n d i x   A                 E m e r g i n g   G r o w t h   S e r i e s
- -------------------                 -------------------------------------------

>  Investment Techniques and Practices

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

   *May be changed only with shareholder approval.

                                      A-1
<PAGE>

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

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

   *May be changed only with shareholder approval.

                                      A-2
<PAGE>

- -------------------                             -------------------------------
A p p e n d i x   A                             U t i l i t i e s   S e r i e s
- -------------------                             -------------------------------

>  Investment Techniques and Practices

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

   *May be changed only with shareholder approval.

                                      A-3
<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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