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] RESEARCH SERIES
MFS[RegTM] UTILITIES SERIES
- --------------------------------------------------------------------------------
This Prosectus describes two of the series of the MFS Variable Insurance Trust
(referred to as the trust):


1. MFS Research Series seeks to provide long-term growth of capital and future
   income (referred to as the Research Series); and

2. 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>
                                                                     Page
<S>                                                                   <C>
I     Expense Summary ............................................      1

II    Risk Return Summary ........................................      2

      1. Research Series .........................................      2

      2. Utilities Series ........................................      5

III   Certain Investment Strategies and Risks ....................     10

IV    Management of the Series ...................................     10

V     Description of Shares ......................................     10

VI    Other Information ..........................................     11

VII   Financial Highlights .......................................     12

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

<PAGE>

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


    I EXPENSE SUMMARY

>    Expense Table

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


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

<TABLE>
<CAPTION>
                                                          Research     Utilities
                                                           Series       Series
                                                         ----------   ----------
<S>                                                          <C>          <C>  
   Management Fee ....................................       0.75%        0.75%
   Other Expenses(1) .................................       0.11%        0.26%
                                                             ----         ----
   Total Annual Series Operating Expenses(1) .........       0.86%        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>  
   Research Series         88      274       477      1,061
   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: Research Series
     ........................................................................ .

>    Investment Objective

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

>    Principal Investment Policies

     The series invests, under normal market conditions, at least 80% of its
     total assets in common stocks and related securities, such as preferred
     stocks, convertible securities and depositary receipts. The series focuses
     on companies that MFS believes have favorable prospects for long-term
     growth, attractive valuations based on current and expected earnings or
     cash flow, dominant or growing market share, and superior management. The
     series may invest in companies of any size. The series' investments may
     include securities traded on securities exchanges or in the
     over-the-counter markets.

     A committee of investment research analysts selects portfolio securities
     for the series. This committee includes investment analysts employed not
     only by MFS, but also by MFS International (U.K.) Limited, a wholly owned
     subsidiary of MFS. The committee allocates the series' assets among various
     industries. Individual analysts then select what they view as the
     securities best suited to achieve the series' investment objective within
     their assigned industry responsibility.

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


>    Principal Risks

     The principal risks of investing in the series and the circumstances
     reasonably likely to cause the value of your investment in the series to
     decline are described below. As with any non-money market mutual fund, the
     share price of the series will change daily based on market conditions and
     other factors. Please note that there are many circumstances which could
     cause the value of your investment in the series to decline, and which
     could prevent the series from achieving its 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 Company Risk: Prices of securities react to the economic condition of the
       company that issued the security. The series' equity investments in an
       issuer may rise and fall based on the issuer's actual and anticipated
       earnings, changes in management and the potential for takeovers and
       acquisitions.

     o Over-the-Counter Risk: Over-the-counter (OTC) transactions involve risks
       in addition to those incurred by 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 exchangelisted stocks. The values of these stocks
       may be more volatile than exchange-listed stocks, and the series may
       experience difficulty in purchasing or selling these securities at a fair
       price.

     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.

                                       2
<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 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    22.33%
     1997    20.26%
     1998    23.39%

[End Bar Chart]

     During the period shown in the bar chart, the highest quarterly return was
   21.65% (for the calendar quarter ended December 31, 1998) and the lowest
   quarterly return was (14.66)% (for the calendar quarter ended September 30,
   1998).


                                       3
<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>
   Research Series*                                   +23.39%       +22.52%
   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 26, 1995, through December 31, 1998.

     ** Source: CDA/Wiesenberger. "Life" refers to the period from August 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.


>    Portfolio Manager

     The series is currently managed by a committee comprised of various equity
     research analysts employed by the Adviser. The committee has managed the
     series since its inception.

                                       4
<PAGE>

     2: 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.


                                       5
<PAGE>

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

     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.


                                       6
<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:

         + 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.

         + 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.

         + 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.

                                       7
<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).


                                       8
<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.

                                       9
<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.


                                       10
<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.

     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.

                                       11
<PAGE>

>    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.


                                       12
<PAGE>

   1. Research 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 ................... $  15.80    $  13.13     $ 10.89        $ 10.00
                                                               -------    --------     -------        -------
   Income from investment operations# --
    Net investment income[sec] .............................. $   0.06    $   0.05     $  0.06        $  0.05
    Net realized and unrealized gain on investments and
     foreign currency .......................................     3.59        2.62        2.37           1.01
                                                               -------    --------     -------        -------
      Total from investment operations ...................... $   3.65    $   2.67     $  2.43        $  1.06
                                                               -------    --------     -------        -------
   Less distributions declared to shareholders --
    From net investment income .............................. $  (0.03)   $     --     $ (0.02)       $ (0.03)
    From net realized gain on investments and foreign
     currency transactions ..................................    (0.37)         --       (0.16)         (0.14)
    In excess of net realized gain on investments and
     foreign currency transactions ..........................       --          --       (0.01)            --
                                                               --------   --------     -------        -------
      Total distributions declared to shareholders .......... $  (0.40)   $     --     $ (0.19)       $ (0.17)
                                                               --------   --------     -------        -------
   Net asset value -- end of period ......................... $  19.05    $  15.80     $ 13.13        $ 10.89
                                                               --------   --------     -------        -------
   Total return .............................................    23.39%      20.26%      22.33%         10.62%++
   Ratios (to average net assets)/Supplemental data[sec]:
    Expenses## ..............................................     0.86%       0.92%       1.01%          1.02%+
    Net investment income ...................................     0.33%       0.34%       0.47%          1.15%+
   Portfolio turnover .......................................       83%         99%         56%            28%
   Net assets at end of period (000 omitted) ................ $567,778    $285,845     $35,710         $2,530
</TABLE>

   ---------
   *     For the period from the commencement of the series' investment
         operations, July 26, 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, 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 or under this limitation, the
         net investment income (loss) per share and the ratios would have been:


<TABLE>
    <S>                                           <C>   <C>        <C>        <C>
    Net investment income (loss) ..........       --    $ 0.06     $   --     $ (0.08)
    Ratios (to average net assets):
     Expenses## ...........................       --      0.88%      1.48%       3.90%+
     Net investment income (loss) .........       --      0.38%        --       (1.73)%+
</TABLE>


                                       13
<PAGE>

     2. 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>


                                       14
<PAGE>



     A p p e n d i x  A                             R e s e a r c h  S e r i e s

    
>    Investment Techniques and Practices

     In pursuing its investment objective and investment policies, the Research
     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                                                                --
  Equity Securities                                             [check mark] 
  Foreign Securities Exposure
   Brady Bonds                                                           --
   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                                                      --
  Indexed Securities/Structured Products                        [check mark] 
  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                                         --
   Options on Futures Contracts                                          --
   Options on Securities                                                 --
   Options on Stock Indices                                              --
   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                                               --
- --------------------------------------------------------------------------------
</TABLE>

*May be changed only with shareholder approval.

                                      A-1
<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>
  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-2
<PAGE>

   MFS[RegTM] VARIABLE INSURANCE TRUST (SM)

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

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

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

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

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

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

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

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


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



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




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