MFS MUNICIPAL SERIES TRUST 485BPOS

Name of

Committee

Number of
Meetings in
Last Fiscal
Year

Functions

Current Members¹

COMPLIANCE AND GOVERNANCE COMMITTEE

Oversees the development and implementation of the Fund’s regulatory and fiduciary compliance policies, procedures, and practices under the 1940 Act, and other applicable laws, as well as oversight of compliance policies of the Fund’s investment adviser and certain other service providers as they relate to Fund activities. The Fund’s Independent Chief Compliance Officer assists the Committee in carrying out its responsibilities. In addition, the Committee advises and makes recommendations to the Board on matters concerning Trustee practices and recommendations concerning the functions and duties of the committees of the Board.

Butler*, Cohn*, Gunning*, Gutow*, and Sherratt*

CONTRACTS REVIEW COMMITTEE

Requests, reviews, and considers the information deemed reasonably necessary to evaluate the terms of the investment advisory and principal

All Independent Trustees of the Board (Butler, Cohn, Gunning, Gutow, Hegarty, Ives,

485BPOS 1 d485bpos.htm MFS MUNICIPAL SERIES TRUST 485BPOS MFS MUNICIPAL SERIES TRUST 485BPOS

As filed with the Securities and Exchange Commission on July 28, 2008

1933 Act File No. 2-92915

1940 Act File No. 811-4096

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

FORM N-1A

REGISTRATION STATEMENT

UNDER

THE SECURITIES ACT OF 1933

POST-EFFECTIVE AMENDMENT NO. 48

AND REGISTRATION STATEMENT

UNDER

THE INVESTMENT COMPANY ACT OF 1940

AMENDMENT NO. 49

MFS^® MUNICIPAL SERIES TRUST

(Exact Name of Registrant as Specified in Charter)

500 Boylston Street, Boston, Massachusetts 02116

(Address of Principal Executive Offices)

Registrant’s Telephone Number, Including Area Code: (617) 954-5000

Susan S. Newton, Massachusetts Financial Services Company,

500 Boylston Street, Boston, Massachusetts 02116

(Name and Address of Agent for Service)

APPROXIMATE DATE OF PROPOSED PUBLIC OFFERING:

It is proposed that this filing will become effective (check appropriate box)

¨	immediately upon filing pursuant to paragraph (b)

x	on July 29, 2008 pursuant to paragraph (b)

¨	60 days after filing pursuant to paragraph (a)(i)

¨	on [date] pursuant to paragraph (a)(i)

¨	75 days after filing pursuant to paragraph (a)(ii)

¨	on [date] pursuant to paragraph (a)(ii) of rule 485

If appropriate, check the following box:

¨	this post-effective amendment designates a new effective date for a previously filed post-effective amendment

Class A Shares

Class B Shares

Class C Shares

MFS^® Municipal Income Fund

Prospectus August 1, 2008

This Prospectus describes the MFS Municipal Income Fund. The investment objective of the fund is to seek total return with an emphasis on income exempt from federal income tax, but also considering capital appreciation.


RISK RETURN SUMMARY		1
EXPENSE SUMMARY		9
MANAGEMENT OF THE FUND		12
DESCRIPTION OF SHARE CLASSES		16
HOW TO PURCHASE, REDEEM, AND EXCHANGE SHARES		25
OTHER INFORMATION		36
FINANCIAL HIGHLIGHTS		40

The Securities and Exchange Commission has not approved or disapproved the fund’s shares or determined whether this prospectus is accurate or complete. Anyone who tells you otherwise is committing a crime.

RISK RETURN SUMMARY

Investment Objective

The fund’s investment objective is to seek total return with an emphasis on income exempt from federal income tax, but also considering capital appreciation. The fund’s objective may be changed without shareholder approval.

Principal Investment Strategies

The fund invests, under normal market conditions, at least 80% of its net assets in securities and other investments, the interest on which is exempt from federal income tax. This policy may not be changed without shareholder approval. Interest from the fund’s investments may be subject to the federal alternative minimum tax.

MFS (Massachusetts Financial Services Company, the fund’s investment adviser) normally invests the fund’s assets primarily in municipal instruments.

MFS primarily invests the fund’s assets in investment grade debt instruments, but may also invest in lower quality debt instruments.

MFS may invest 25% or more of the fund’s total assets in municipal instruments that finance similar projects, such as those relating to education, healthcare, housing, utilities, water, or sewers.

MFS may use derivatives for different purposes, including to earn income and enhance returns, to increase or decrease exposure to a particular market, to manage or adjust the risk profile of the fund, or as alternatives to direct investments.

MFS uses a bottom-up investment approach in buying and selling investments for the fund. Investments are selected primarily based on fundamental analysis of instruments and their issuers in light of current market, economic, political, and regulatory conditions. Factors considered may include the instrument’s credit quality, collateral characteristics, and indenture provisions, and the issuer’s management ability, capital structure, leverage, and ability to meet its current obligations. Quantitative analysis of the structure of the instrument and its features may also be considered.

MFS may engage in active and frequent trading in pursuing the fund’s principal investment strategies.

In response to market, economic, political, or other conditions, MFS may depart from the fund’s principal investment strategies by temporarily investing for defensive purposes.

Principal Investment Types

Debt Instruments: Debt instruments represent obligations of corporations, governments, and other entities to repay money borrowed. The issuer or borrower usually pays a fixed, variable, or floating rate of interest, and must repay the amount borrowed, usually at the maturity of the instrument. Some debt instruments, such as zero coupon bonds or payment-in-kind bonds, do not pay current interest. Other debt instruments, such as certain mortgage-backed and other asset-backed securities, make periodic payments of interest and/or principal. Some debt instruments are partially or fully secured by collateral supporting the payment of interest and principal.

Lower Quality Debt Instruments: Lower quality debt instruments, commonly referred to as “high yield securities” or “junk bonds,” are debt instruments of less than investment grade quality.

Municipal Instruments: Municipal instruments are issued to raise money for a variety of public and private purposes, including general financing for state and local governments, or financing for a specific project or public facility. Municipal instruments include general obligation bonds of municipalities, local or state governments, project or revenue-specific bonds, municipal lease obligations, and prerefunded or escrowed bonds. Municipal instruments may be fully or partially supported by the local government, by the credit of a private issuer, by the current or anticipated revenues from a specific project or assets, by the issuer’s pledge to make annual appropriations for lease payments, or by domestic or foreign entities providing credit support, such as letters of credit, guarantees, or insurance.

Derivatives: Derivatives are financial instruments whose value is based on the value of one or more underlying indicators or the difference between underlying indicators. Underlying indicators may include a security or other financial instrument, asset, currency, interest rate, credit rating, commodity, volatility measure, or index. Derivatives often involve a counterparty to the transaction. Derivatives include futures, forward contracts, options, structured securities, inverse floating rate instruments, swaps, caps, floors, and collars.

Principal Risks

As with any mutual fund, you could lose money on your investment in the fund. An investment in the fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency.

The principal risks of investing in the fund are:

Interest Rate Risk: The price of a debt instrument changes in response to interest rate changes. In general, the price of a debt instrument falls when interest rates rise and rises when interest rates fall. Instruments with longer maturities, or that do not pay current interest, are more sensitive to interest rate changes. In addition, short-term and long-term interest rates do not necessarily move in the same direction or by the same amount. An instrument’s reaction to interest rate changes depends on the timing of its interest and principal payments and the current interest rate for each of those time periods. Instruments with floating interest rates can be less sensitive to interest rate changes. In response to an interest rate decline, instruments that provide the issuer with the right to call or redeem the instrument prior to maturity may be called or redeemed, resulting in the reinvestment of proceeds in other investments at a lower interest rate.

Credit Risk: The value of a debt instrument depends, in part, on the issuer’s or borrower’s credit quality or ability to pay principal and interest when due. The value of a debt instrument is likely to fall if an issuer or borrower defaults on its obligation to pay principal or interest or if the instrument’s credit rating is downgraded by a credit rating agency. The value of a debt instrument can also decline in response to changes in the financial condition of the issuer or borrower, changes in specific market, economic, industry, political, and regulatory conditions that affect a particular type of instrument, issuer, or borrower, and changes in general market, economic, political, and regulatory conditions. Certain unanticipated events, such as natural disasters, terrorist attacks, war, and other geopolitical events can have a dramatic adverse effect on the value of a debt instrument. For certain types of instruments, including derivatives, the value of the instrument depends in part on the credit quality of the counterparty to the transaction. For other types of debt instruments,

including collateralized instruments, the price of the debt instrument also depends on the credit quality and adequacy of the underlying assets or collateral. Enforcing rights against the underlying assets or collateral may be difficult, or the underlying assets or collateral may be insufficient, if the issuer defaults.

Municipal instruments supported as to the payment of principal and interest only by the revenue from a specific project or specific assets, or by the issuer’s pledge to make annual appropriations for lease payments, are subject to greater credit risk due to the possibility that taxation supporting the project or assets will be discontinued, revenues for the project or from the assets will be insufficient, or annual appropriations for lease payments will not be made. If the Internal Revenue Service or a state taxing authority determines that an issuer of a municipal instrument has not complied with applicable tax requirements, interest from the instrument could become taxable (including retroactively) and the instrument could decline significantly in value.

Lower quality debt instruments and certain unrated debt instruments can involve a substantially greater risk of default or can already be in default, and their values can decline significantly over short periods of time. Lower quality debt instruments are regarded as having predominantly speculative characteristics with respect to capacity to pay interest and principal. Lower quality debt instruments tend to be more sensitive to adverse news about the issuer, or the market or economy in general, than higher quality debt instruments. The market for lower quality debt instruments and certain unrated debt instruments can be less liquid, especially during periods of recession or general market decline.

Prepayment Risk: Many types of debt instruments, including mortgage-backed securities, asset-backed securities, and municipal housing bonds, are subject to the risk of prepayment. Prepayment occurs when unscheduled payments of principal are made prior to an instrument’s maturity. Instruments subject to prepayment can offer less potential for gains during a declining interest rate environment and greater potential for loss in a rising interest rate environment. In addition, prepayment rates are difficult to predict and the potential impact of prepayment on the price of a debt instrument depends on the terms of the instrument and can result in significant volatility.

Because many municipal instruments are issued to finance similar projects, especially those relating to education, health care, housing, utilities, and water and sewer, conditions in these industries can affect the overall municipal market. In addition, changes in the financial condition of an individual municipal insurer can affect the overall municipal market.

Derivatives Risk: Derivatives can be highly volatile and involve risks in addition to the risks of the underlying indicator(s). Gains or losses from derivatives can be substantially greater than the derivatives’ original cost, and can sometimes be unlimited, and therefore, can involve leverage. Derivatives can be complex instruments and can involve analysis and processing that differs from that required for other investment types used by the fund. If the value of a derivative does not correlate well with the particular market or other asset class the derivative is intended to provide exposure to, the derivative may not have the effect anticipated. Derivatives can also reduce the opportunity for gains or result in losses by offsetting positive returns in other investments. Derivatives can be less liquid than other types of investments.

Leveraging Risk: Certain transactions, including when-issued, delayed-delivery, and forward commitment purchases, and the use of some derivatives, can result in leverage. Leverage involves investment exposure in an amount exceeding the initial investment. In transactions involving leverage, a relatively small change in an underlying indicator can lead to significantly larger losses to the fund. Leverage can cause increased volatility by magnifying gains or losses.

Investment Selection Risk: The MFS analysis of an investment can be incorrect and its selection of investments can lead to an investment focus that results in the fund underperforming other funds with similar investment strategies and/or underperforming the markets in which the fund invests.

Counterparty and Third Party Risk: Transactions involving a counterparty other than the issuer of the instrument, or a third party responsible for servicing the instrument, are subject to the credit risk of the counterparty or third party, and to the counterparty’s or third party’s ability to perform in accordance with the terms of the transaction.

Liquidity Risk: Certain investments and types of investments are subject to restrictions on resale, may trade in the over-the-counter market or in limited volume, or may not have an active trading market. As a result, it may not be possible to sell the investment at any particular time or at an acceptable price.

Frequent Trading Risk: Frequent trading increases transaction costs, which may reduce the fund's return. Frequent trading can also result in the realization of a higher percentage of short-term capital gains and a lower percentage of long-term capital gains as compared to a fund that trades less frequently. Because short-term capital gains are distributed as ordinary income, this would generally increase your tax liability unless you hold your shares through a tax-deferred or tax-exempt vehicle.

Defensive Investing Risk: When MFS invests defensively, different factors could affect the fund’s performance and the fund may not achieve its investment objective. In addition, the defensive strategy may not work as intended.

Further Information Available

Information about investment strategies and investment types not described in the Prospectus and the risks associated with those investment strategies and investment types are described in the fund’s Statement of Additional Information (“SAI”).

Bar Chart and Performance Table

The bar chart and performance table below are intended to indicate some of the risks of investing in the fund by showing changes in the fund’s performance over time. The performance table also shows:

•

how the fund’s performance over time compares with that of a broad measure of market performance, and

•

returns before the deduction of taxes and returns after the deduction of certain taxes for Class A shares.

The chart and table provide past performance information. The fund’s past performance (before and after taxes) does not necessarily indicate how the fund will perform in the future. The performance information in the chart and table is based upon calendar year periods, while the performance information presented under the caption “Financial Highlights” and in the fund's shareholder reports is based upon the fund’s fiscal year. Therefore, these performance results may differ.

Bar Chart. The bar chart shows changes over time in the annual total return of the fund’s Class A shares for the past ten calendar years, and

assumes the reinvestment of distributions. The chart and related notes do not take into account any sales charges (loads) that you may be required to pay upon purchase or redemption of the fund’s shares. If these sales charges were included, they would reduce the returns shown. The return of the fund’s other classes of shares will differ from the Class A share returns shown in the bar chart, depending upon the expenses of those classes.

LOGO

The total return for the six-month period ended June 30, 2008 was (0.26)%. During the periods shown in the bar chart, the highest quarterly return was 4.37% (for the calendar quarter ended September 30, 2002) and the lowest quarterly return was (2.03)% (for the calendar quarter ended June 30, 2004).

Performance Table. This table shows how the average annual total returns of each class of the fund, before the deduction of taxes (“Returns Before Taxes”), compare to a broad measure of market performance, and assumes the deduction of the maximum applicable sales loads (initial sales charge and/or contingent deferred sales charge (CDSC), as applicable), and the reinvestment of distributions. In addition, for Class A shares, this table shows Class A average annual total returns:

•

after the deduction of taxes on distributions made on Class A shares, such as capital gains and income distributions (“Class A Shares’ Return After Taxes on Distributions”), and

•

after the deduction of taxes on both distributions made on Class A shares and on redemption of Class A shares, assuming that the shares are redeemed at the end of the periods for which returns are shown (“Class A Shares’ Return After Taxes on Distributions and Sale of Class A Shares”).

Average Annual Total Returns (for the Periods Ended December 31, 2007)


Share Class	1 Year		5 Years		10 Years
Returns Before Taxes
B Shares, with CDSC (Declining over Six Years from 4% to 0%)	(2.06	)%	3.34	%	3.82	%
C Shares, with CDSC (1% for 12 Months)	0.87	%	3.70	%	3.83	%
A Shares, With Initial Sales Charge (4.75%)	(2.26	)%	3.44	%	4.09	%
Returns After Taxes (Class A Shares Only)
A Shares’ Return After Taxes on Distributions, with Initial Sales Charge (4.75%)	(2.28	)%	3.44	%	4.06	%
A Shares’ Return After Taxes on Distributions and Sale of Class A Shares, with Initial Sales Charge (4.75%)	0.14	%	3.63	%	4.19	%
Benchmark Comparison (Returns Before Taxes)
Lehman Brothers Municipal Bond Index*†	3.36	%	4.30	%	5.17	%

*	The Lehman Brothers Municipal Bond Index is a market capitalization-weighted index that measures the performance of the tax-exempt bond market.

†	Source: FactSet Research Systems Inc.

All performance results reflect any applicable fee and expense waivers in effect during the periods shown; without these, the results would have been lower.

After-tax returns are calculated using the historical highest individual federal marginal income tax rates, and do not reflect the impact of state and local taxes. Your actual after-tax returns will depend on your own tax situation, and may differ from those shown. The after-tax returns shown are not relevant to investors who hold their shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. The after-tax returns are shown for only one of the fund’s classes of shares, and after-tax returns for the fund’s other classes of shares will vary from the returns shown.

The fund commenced investment operations on December 29, 1986, with the offering of Class B shares, and subsequently offered Class A shares on September 7, 1993, and Class C shares on January 3, 1994.

EXPENSE SUMMARY

Expense Table

This table describes the fees and expenses that you may pay when you buy, redeem, and hold shares of the fund. The annual fund operating expenses are based on expenses incurred during the fund’s most recently completed fiscal year, adjusted to reflect annualized expenses and the management fee set forth in the fund’s Investment Advisory Agreement. The fund’s annual operating expenses may vary in future years.

Shareholder Fees (fees paid directly from your investment):


Share Class	A		B		C
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	4.75	%	N/A		N/A
Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less)	See Below	^(#)	4.00	%	1.00	%
Annual Fund Operating Expenses of Class A for Each Fund (expenses that are deducted from fund assets):
Management Fee	0.40	%	0.40	%	0.40	%
Distribution and/or Service (12b-1) Fees⁽¹⁾	0.25	%	1.00	%	1.00	%
Other Expenses⁽²⁾	0.24	%	0.24	%	0.24	%

Total Annual Fund Operating Expenses⁽²⁾	0.89	%	1.64	%	1.64	%
Fee Reductions⁽³⁾	(0.05	)%	(0.05	)%	(0.05	)%

Net Expenses⁽²⁾	0.84	%	1.59	%	1.59	%

A contingent deferred sales charge (referred to as a CDSC) of 1% may be deducted from your redemption proceeds if you buy $1 million or more of Class A shares and you redeem your investment within 12 months of your purchase if you purchased shares prior to September 1, 2008, and within 24 months of your purchase if you purchased shares on or after September 1, 2008.

(1)

The fund’s Rule 12b-1 plan permits it to pay distribution and/or service fees to support the sale and distribution of the fund’s Class A, Class B, and Class C shares and the services provided by financial intermediaries. The maximum rates that may be charged under the plan, together with details of any fee reduction arrangements, are set forth under “Distribution and Service Fees.”

(2)

expense and fees in the amount of 0.09% related to the fund’s investments in inverse floating rate investments. Under accounting rules, the fund recognizes additional income in an amount equal to these expenses. Therefore, the fund’s net asset values per share and performance have not been affected by these expenses. However, these expenses are included in the fund’s “Total Annual Fund Operating Expenses” and “Net Expenses” in the table above, and in the “Example of Expenses” below. Had these expenses and fees not been included, “Net Expenses” would have been 0.75% for Class A shares, and 1.50% for both Class B shares and Class C shares.

(3)

MFS has agreed in writing to reduce the fund’s management fee to 0.30% annually until February 28, 2009. See “Management of the Fund – Investment Adviser”. Such fee reduction is not reflected in the table. Had this fee reduction been taken into account, “Total Annual Fund Operating Expenses” would have been lower. In addition, MFS has agreed in writing to bear the fund’s expenses such that “Other Expenses,” determined without giving effect to the expense offset arrangement described above, do not exceed 0.10% annually for each of Class A shares, Class B shares, and Class C shares. This written agreement excludes management fees, distribution and service fees, interest, taxes, extraordinary expenses, brokerage and transaction costs and investment-related expenses (including interest expenses and fees associated with investments in inverse floating rate instruments) and will continue until at least July 31, 2009.

Example of Expenses

These examples are intended to help you compare the cost of investing in the fund with the cost of investing in other mutual funds.

The examples assume that:

•

You invest $10,000 in the fund for the time periods indicated and you redeem your shares at the end of the time periods (unless otherwise indicated);

•

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

•

The fund’s operating expenses remain the same, except that the fund’s total operating expenses are assumed to be the fund’s “Net Expenses” for the period during which any written fee reductions are in effect (see “Expense Summary - Expense Table” above).

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


Share Class	1 Year		3 Years		5 Years		10 Years
A shares	$	557	$	741	$	940	$	1,515
B shares⁽¹⁾
Assuming redemption at end of period	$	562	$	812	$	1,087	$	1,739
Assuming no redemption	$	162	$	512	$	887	$	1,739
C shares
Assuming redemption at end of period	$	262	$	512	$	887	$	1,939
Assuming no redemption	$	162	$	512	$	887	$	1,939

(1)	Class B shares convert to Class A shares approximately eight years after purchase; therefore, years nine and ten reflect Class A expenses.

MANAGEMENT OF THE FUND

Investment Adviser

Massachusetts Financial Services Company (“MFS”), located at 500 Boylston Street, Boston, Massachusetts, serves as the investment adviser for the fund. Subject to the supervision of the fund’s Board of Trustees, MFS is responsible for managing the fund’s investments, executing transactions and providing related administrative services and facilities under an Investment Advisory Agreement between the fund and MFS.

For the fiscal year ended March 31, 2008, the fund paid MFS an effective management fee equal to 0.30% of the fund’s average daily net assets.

The management fee set forth in the Investment Advisory Agreement is 0.40% annually of the fund’s average daily net assets. MFS has agreed in writing to reduce its management fee to 0.30% annually of the fund’s average daily net assets. MFS has agreed to maintain this management fee reduction until February 28, 2009, as part of its settlement with the New York Attorney General concerning market timing and related matters.

Additionally, effective March 1, 2009, MFS has agreed in writing to reduce its management fee to 0.37% annually in excess of $1.3 billion of the fund’s average daily net assets, and to 0.35% annually in excess of $2.0 billion of the fund’s average daily net assets. This written agreement will remain in effect until at least July 31, 2009 or until modified by the fund’s Board of Trustees.

A discussion regarding the basis for the Board of Trustees’ approval of the Investment Advisory Agreement is available in the fund’s most recent semi-annual report for the six-month period that ends September 30.

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 $184 billion as of March 31, 2008.

courts. The various lawsuits that are still pending generally allege that some or all of the defendants permitted or acquiesced in market timing and/or late trading in some of the MFS funds, and inadequately disclosed MFS’ internal policies concerning market timing and such matters. The pending lawsuits assert that some or all of the defendants violated the federal securities laws, including the Securities Act of 1933, the Securities Exchange Act of 1934, the Investment Company Act of 1940, and the Investment Advisers Act of 1940, as well as fiduciary duties and other violations of common law. The pending lawsuits variously have been commenced as class actions or individual actions on behalf of investors who purchased, held, or redeemed shares of the MFS funds during specified periods, or as derivative actions on behalf of the MFS funds.

The lawsuits relating to market timing and related matters have been transferred to, and consolidated before, the United States District Court for the District of Maryland, as part of a multi-district litigation of market timing and related claims involving several other fund complexes (In re Mutual Funds Investment Litigation (Alger, Columbia, Janus, MFS, One Group, Putnam, Allianz Dresdner), No. 1:04-md-15863 (transfer began March 19, 2004)). The pending market timing cases related to the MFS funds include Riggs v. MFS et al., Case No. 04-CV-01162-JFM (consolidated class action complaint filed September 30, 2004), Hammerslough v. MFS et al., Case No. 04-MD-01620 (consolidated derivative complaint filed September 30, 2004), and Reaves v. MFS Series Trust I, et al., Case No. 1:05-CV-02220-JFM (complaint related to Class B shares filed March 21, 2005). The plaintiffs in these consolidated lawsuits generally seek injunctive relief including removal of the named Trustees, adviser and distributor, rescission of contracts and 12b-1 Plans, disgorgement of fees and profits, monetary damages, punitive damages, attorney’s fees and costs and other equitable and declaratory relief. Insofar as any of the actions is appropriately brought derivatively on behalf of any of the MFS funds, any recovery will inure to the benefit of the MFS funds. Several claims of the various lawsuits have been dismissed; MFS and the other named defendants continue to defend the various lawsuits.

Disclosure of Portfolio Holdings. The MFS funds have established a policy with respect to the disclosure of fund portfolio holdings. A description of this policy is provided in the SAI. In addition, by clicking on a fund name under “Select a fund” on the MFS Web site (mfs.com), the following information is generally available to you:


Information		Approximate Date of Posting to Web Site
Fund’s top 10 securities holdings as of each month’s end		14 days after month end
Fund’s full securities holdings as of each month’s end		24 days after month end

If a fund has substantial investments in both equity and debt instruments, the fund’s top 10 equity holdings and top 10 debt holdings will be made available.

Note that the funds or MFS may suspend the posting of this information or modify the elements of this web posting policy without notice to shareholders. Once posted, the above information will remain available on the Web site until at least the date on which the fund files a Form N-CSR or Form N-Q for the period that includes the date as of which the Web site information is current.

Portfolio Manager(s)

Information regarding the portfolio manager(s) of the fund is set forth below. Further information regarding the portfolio manager(s), including other accounts managed, compensation, ownership of fund shares, and possible conflicts of interest, is available in the fund’s SAI. The portfolio manager is primarily responsible for the day-to-day management of the fund.


Portfolio Manager	Primary Role	Since	Title and Five Year History
Geoffrey L. Schechter	Portfolio Manager	2000	Investment Officer of MFS; employed in the investment management area of MFS since 1993.

Administrator

MFS provides the fund with certain financial, legal, and other administrative services under a Master Administrative Services Agreement between the fund and MFS. Under the Agreement, MFS is paid an annual fee for 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 fund.

Shareholder Servicing Agent

MFS Service Center, Inc. (“MFSC”), a wholly owned subsidiary of MFS, provides dividend and distribution disbursing and transfer agent and recordkeeping functions in connection with the issuance, transfer, and redemption of each class of shares of the fund under a Shareholder Servicing Agent Agreement. MFSC receives a fee based on the costs it incurs in providing these services and a target profit margin. In addition, MFSC is reimbursed for payments made to service providers that provide certain sub-accounting and other shareholder services (shareholder servicing payments) and out-of-pocket expenses.

DESCRIPTION OF SHARE CLASSES

The fund offers Class A, Class B, and Class C shares through this prospectus. The fund also offers additional classes of shares, Class A1 and Class B1 shares, which are available through a separate prospectus provided to investors eligible to purchase them.

Sales Charges and Waivers or Reductions

You may be subject to an initial sales charge when you purchase Class A, or a CDSC when you redeem Class A, Class B, or Class C shares. These sales charges are paid to MFD.

In the circumstances described below, you may qualify for a sales charge waiver or reduction for purchases or redemptions of Class A, Class B, or Class C shares. In addition, other sales charge waivers or reductions may apply to certain transactions by retirement plans, section 529 tuition programs, and certain other groups (e.g., affiliated persons of MFS) and with respect to certain types of investment programs (e.g., certain wrap accounts or fund supermarket investments). Details regarding the types of investment programs and categories of investors eligible for these waivers or reductions are provided in the SAI, which is available to you free of charge, and on the fund’s Web site at mfs.com. Some of these programs and waivers or reductions may not be available to you if your shares are held through certain types of accounts, such as retirement accounts and 529 plans, or certain accounts that you may have with your financial intermediary. Waivers or reductions may be eliminated, modified, and added at any time without providing advance notice to shareholders.

Class A Shares. You may purchase Class A shares at the offering price (which includes the applicable initial sales charge). In some cases, you may purchase Class A shares without an initial sales charge; in these cases, you will generally be subject to a 1% CDSC upon redemption within 12 months of your purchase.

The amount of the initial sales charge you pay when you buy Class A shares differs depending upon the amount you invest, as follows:


	*Initial Sales Charge As Percentage Of:**
Amount of Purchase	Gross Purchase Amount (Offering Price*)		Net Amount Invested
Less than $50,000	4.75	%	4.99	%
$50,000 but less than $100,000	4.25	%	4.44	%
$100,000 but less than $250,000	3.75	%	3.90	%
$250,000 but less than $500,000	2.75	%	2.83	%
$500,000 but less than $1,000,000	2.00	%	2.04	%
$1,000,000 or more	None	**	None	**

*	Offering price is calculated by dividing the net asset value of a share by the difference between 1 and the initial sales charge percentage. Because the offering price is rounded to two decimal places, actual sales charges you pay may be more or less than those calculated using these percentages.

**	A 1% CDSC will generally apply to such purchases.

You pay no initial sales charge when you invest $1 million or more in Class A shares. However, for purchasers other than Employer Retirement Plans, a CDSC of 1% will generally be deducted from your redemption proceeds if you redeem within 12 months of your purchase if you purchased shares prior to September 1, 2008, and within 24 months of your purchase if you purchased shares on or after September 1, 2008.

Class B Shares. You may purchase Class B shares at net asset value without an initial sales charge, but if you redeem your shares within the first six years after purchase, you may be subject to a CDSC (declining from 4% during the first year to 0% after six years).

The CDSC is imposed according to the following schedule:


Year of redemption after purchase	1st		2nd		3rd		4th		5th		6th		7th
Contingent deferred sales charge	4	%	4	%	3	%	3	%	2	%	1	%	0	%

If you hold Class B shares for approximately eight years, they will convert to Class A shares of the fund. All Class B shares you acquire through the reinvestment of dividends and distributions will be held in a separate sub-account. Each time any Class B shares in your account convert to Class A shares, a proportionate number of the Class B shares in the sub-account will also convert to Class A shares.

Class C Shares. You may purchase Class C shares at net asset value without an initial sales charge. However, a CDSC of 1% will generally be deducted from your redemption proceeds if you redeem within 12 months of your purchase.

Sales Charge Waivers or Reductions. Below is a summary of certain investor programs whereby the applicable sales charge may be waived or reduced. You or your financial intermediary must inform MFSC upon purchasing fund shares of your intention to invest in a fund under one of the programs below. You can provide this information in your account application or through a separate document provided by your financial intermediary.


Program	Investments Eligible For:
Program	Waived Initial Sales Charge	Reduced Initial Sales Charge	Waived CDSC
Letter of Intent		X
Right of Accumulation		X
Automatic Exchange Plan	X*
Exchange Privilege	X*
Systematic Withdrawal Plan			X**
Distribution Reinvestment	X
Distribution Investment Program	X
Other Sales Charge Waivers	X		X

*	Investments under the Automatic Exchange Plan or certain other exchanges under the Exchange Privilege may be subject to a sales charge in certain cases.

**	Not available for Class A shares and limited for Class B and Class C shares.

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Letter Of Intent (LOI). You may pay a reduced or no initial sales charge on purchases of Class A shares if you intend to invest a specific dollar amount, based on the gross amount of your investment (including the amount of any sales charge paid), including investments through any linked accounts in any class of any MFS fund within a 13-month period (36 months for a $1 million commitment). Distributions reinvested in additional shares of the fund or distributions from other MFS funds automatically invested in shares of the fund will not apply toward the satisfaction of the LOI.

For each purchase you make under the LOI you will pay the initial sales charge rate applicable to the total amount you intended to purchase. If, however, you do not purchase the

intended amount within the relevant time period, your account will be adjusted by redemption of the amount of shares needed to pay the higher initial sales charge level for the amount actually purchased.

To establish a LOI, you may complete the Letter of Intent section of your account application or service application. In order to benefit from the LOI, you or your financial intermediary must inform MFSC that the LOI is in effect each time shares of a fund are purchased.

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Right Of Accumulation (ROA). Under the ROA, you may pay a reduced or no initial sales charge on purchases of Class A shares by aggregating the total dollar amount of your investment with your existing investments or any linked accounts in any class of any MFS fund, based on the current maximum public offering price of the funds. For example, you will pay a sales charge on your current purchase at the rate applicable to the total value of all eligible accounts based on the sales charge schedule above.

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Linking Accounts For LOI And ROA. For purposes of obtaining reduced sales charges under the LOI and ROA, you may combine the value of your current purchase of shares of an MFS fund with the value of existing accounts held with the MFS funds by you, your spouse (or legal equivalent under applicable state law), and your children under the age of 21.

Eligible accounts that you may link under a LOI and ROA may include:

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Individual accounts;

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Joint accounts;

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Trust accounts of which you, your spouse (or legal equivalent under applicable state law), or child under the age of 21 is the grantor;

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MFS 529 College Savings Plan accounts;

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Certain single-participant retirement plan accounts;

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Certain Individual Retirement Accounts;

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Uniform Gifts/Transfers to Minor Acts accounts; and

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Accounts held in the name of your financial intermediary on your behalf, except accounts investing in Class W shares of certain MFS funds.

In order to link such accounts under a LOI or ROA, the broker/dealer at the time of your current purchase must be the broker/dealer (or the clearing broker/dealer for your broker/dealer so long as your account is not aggregated by the clearing broker/dealer with other accounts) for any additional accounts to be linked. MFS fund shares held as follows cannot be combined with your current purchase for purposes of a LOI or ROA:

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Shares held indirectly through financial intermediaries other than the broker/dealer for your current purchase (for example, shares held in a different broker/dealer’s brokerage account or with a bank, an insurance company separate account or an investment adviser); or

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Shares held directly in a MFS fund account on which the broker/dealer is different than the broker/dealer for your current purchase.

It is your responsibility to inform the broker/dealer for each current purchase of any accounts held with the MFS funds that you believe are eligible to be linked under a LOI or a ROA. If you have not designated a broker/dealer, you should inform MFSC directly of any accounts held with the MFS funds that you believe are eligible to be linked under a LOI or a ROA. You should provide your financial intermediary (including MFSC if you have not designated a broker/dealer) with certain supporting information at the time of each purchase regarding accounts held with the MFS funds that are eligible to be combined for purposes of a LOI or ROA. Such information may include shareholder identification numbers or applicable account numbers or account statements. You should request that your financial intermediary provide this information to the funds or their agents when placing each purchase order.

change the broker/dealer for any such account, your accounts will no longer be eligible to be linked under a LOI or ROA. In addition, you will not be able to link additional accounts to the extent they do not meet the criteria discussed above.

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Automatic Exchange Plan. If you have an account balance of at least $2,000 in the fund, you may participate in the automatic exchange plan, a dollar-cost averaging program. This plan permits you to make automatic periodic exchanges from your account in the fund for shares of the same class of other MFS funds. Exchanges will generally be made at net asset value without any sales charges. If you exchange shares out of the MFS Money Market Fund or MFS Government Money Market Fund, or if you exchange Class A shares out of the MFS Cash Reserve Fund into Class A shares of any other MFS fund, you will pay an initial sales charge if you have not already paid this charge on these shares.

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Systematic Withdrawal Plan. If you have an account balance of at least $5,000 in your account in the fund, you may elect to receive (or designate someone else to receive) regular periodic payments (of at least $50 if by check) through an automatic redemption of Class A, Class B, and Class C shares. For Class B and Class C shares, you may incur a CDSC when Class B or Class C shares are redeemed under the plan (or plans if more than one plan is established) if greater than 10% of the value of your account is withdrawn under the plan(s) in any one year (determined at the time of your first withdrawal under the plan(s), or January 1, 2007 with respect to Class B shares, or January 1, 2008 with respect to Class C shares, whichever is later, and reset annually thereafter). For Class A shares, you may incur a CDSC when Class A shares are redeemed under this plan.

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Distribution Reinvestment. You may automatically reinvest dividend and capital gain distributions in the same fund without paying an initial sales charge.

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Distribution Investment Program. You may automatically reinvest dividend and capital gain distributions into the same class of another MFS fund without paying a CDSC or an initial sales charge.

Calculation Of CDSC. As discussed above, certain investments in Class A, Class B, and Class C shares are subject to a CDSC. For purposes of calculating the CDSC, purchases made on any day during a calendar month will age one month on the last day of that month, and on the last day of each subsequent month. For example, a 1% CDSC on Class A shares purchased on August 10 will expire at the close of business on July 31 of the following calendar year, and a redemption of those shares made on or after August 1 of the following calendar year will not be subject to the CDSC.

Shares acquired through reinvestment of distributions are not subject to a CDSC. The CDSC is based on the original purchase cost or the current market value of the shares being sold, whichever is less. For purposes of determining the CDSC, if you sell only some of your shares, shares not subject to a CDSC are sold first, followed by shares held the longest.

Distribution and Service Fees

The fund has adopted a plan in accordance with Rule 12b-1 under the Investment Company Act of 1940, as amended (the “Distribution Plan”). Under the Distribution Plan, the fund pays distribution and service fees to MFD to support the sale and distribution of Class A, Class B, and Class C shares, as well as shareholder servicing and account maintenance activities. These distribution and service fees equal on an annual basis up to the following maximum percentages of average daily net assets of the class:


Class	Maximum Distribution Fee		Maximum Service Fee		Maximum Total Distribution and Service Fee
Class A	0.10	%	0.25	%	0.35	%
Class B	0.75	%	0.25	%	1.00	%
Class C	0.75	%	0.25	%	1.00	%

The Class A distribution fee is currently not in effect but may be implemented on such date as the Board of Trustees may determine.

Financial Intermediary Compensation

The term “financial intermediary” includes any broker/dealer, bank (including bank trust departments), registered investment adviser, financial planner, retirement plan administrator, third-party administrator, insurance company, and any other institutions having a selling, administration, or any similar agreement with MFD, MFS, or one of its affiliates.

Financial intermediaries receive various forms of compensation in connection with the sale of shares of a fund and/or the servicing of shareholder accounts. Financial intermediaries may receive such compensation (i) in the form of up front commissions and ongoing asset-based compensation paid by MFD based on sales charges received and expected to be received by MFD from shareholders and Distribution Plan distribution and service payments received by MFD from the fund, (ii) in the form of shareholder servicing payments paid by MFD and/or one or more of its affiliates (for purposes of this section only, collectively, “MFD”) based on the receipt of such payments by MFD from the fund, and (iii) in the form of payments paid by MFD from MFD’s own additional resources.

The types of payments described above are not exclusive and such payments can be significant to the financial intermediary. In addition, the compensation that financial intermediaries receive may vary by class of shares sold and among financial intermediaries. Depending upon the arrangements in place at any particular time, financial intermediaries may have a financial incentive to recommend a particular fund or share class.

Financial intermediaries may receive up front commissions of up to the following percentage amounts for sales of the following share classes:


Share Class	Up Front Commission as a Percentage of Offering Price
Class A	4.75	%
Class B	3.75	%
Class C	1.00	%

In addition, financial intermediaries may receive payments from MFD from MFD’s own additional resources as incentives to market the MFS funds, to cooperate with MFD’s promotional efforts and/or in recognition of their marketing, administrative services, and/or processing support. This compensation from MFD is not reflected in the fees and expenses listed in the fee table section of the fund’s prospectus. MFD compensates financial intermediaries based on criteria established by MFD from time to time that consider, among other factors, the level and/or type of marketing and administrative support provided by the financial intermediary, the level of assets attributable to and/or sales by the financial intermediary and the quality of the overall relationship with the financial intermediary.

These additional payments by MFD may take the form of payments to financial intermediaries that provide marketing support and administrative services to MFD with respect to fund shares sold or held through the financial intermediary’s retail distribution network and/or through programs such as retirement programs, qualified tuition programs, fund supermarkets, fee-based advisory or wrap fee programs, bank trust programs, and insurance (e.g., individual or group annuity) programs. MFD may also make payments to financial intermediaries to help offset the cost associated with client account maintenance support, statement preparation, and transaction processing. To the extent permitted by SEC and FINRA (Financial Industry Regulatory Authority) rules and other applicable laws and regulations, MFD may make other payments or allow other promotional incentives or payments to financial intermediaries.

You can find further details in the SAI about the payments made by MFD and the services provided by financial intermediaries. Financial intermediaries may charge you additional fees and/or commissions other than those disclosed in this prospectus. You can ask your financial intermediary for information about any payments it receives from MFD and any services it provides, as well as about fees and/or commissions it charges. Financial intermediaries that sell fund shares may also act as a broker/dealer in connection with a MFS fund’s purchase or sale of portfolio securities. However, the fund and MFS do not consider financial intermediaries’ sales of shares of a MFS fund as a factor when choosing broker/dealers to effect portfolio transactions for the MFS funds.

HOW TO PURCHASE, REDEEM, AND EXCHANGE SHARES

You may purchase, redeem, and exchange shares of the fund in the manner described below. If you buy or sell shares of a fund through a retirement account, 529 plan, or financial intermediary, the procedures for buying, selling, and exchanging shares of the fund and the features, policies and fees may differ from those discussed in this prospectus.

How to Purchase Shares

Your shares will be bought at the offering price (the net asset value per share plus any applicable initial sales charge) next calculated after your purchase order is received in proper form. Your financial intermediary is responsible for transmitting your purchase order to the fund in proper form and in a timely manner. MFSC reserves the right to reject any purchase order that is not in proper form. The specific requirements for proper form depend on the type of account and transaction and the method of purchase; contact MFSC if you have questions about your particular circumstances. Certain restrictions apply to the use of a transfer on death registration. You or your financial intermediary should contact MFSC to obtain a Transfer on Death registration form and for information regarding MFSC’s other requirements for transfer on death registrations.

The fund may reject for any reason, or cancel as permitted or required by law, any purchase orders. The fund may stop offering shares completely, or may offer shares only on a limited basis, for a period of time or permanently.

The fund is required by law to obtain from you certain personal information that will be used to verify your identify. If you do not provide the information, the fund may not be able to open your account. The fund must also take certain steps to verify that the account information you provide is correct.

Class A, Class B, and Class C Shares. With respect to Class A, Class B, and Class C shares, you can establish an account by having your financial intermediary process your purchase. The minimum initial investment is generally $1,000, except for: fee-based and wrap accounts offered through certain financial intermediaries, for which there is no minimum initial investment; and IRAs, for which the minimum initial investment is generally $250. In addition, the minimum initial investment is $50 for automatic investment or exchange plans. MFSC waives or lowers the initial investment minimum for certain types of investors and investments.

Purchases of Class B shares are subject to a total account value limitation at the time of purchase of $99,999, and purchases of Class C shares are subject to a total account value limitation at the time of purchase of $999,999. If your existing accounts for all share classes held with the MFS funds have a total value equal to $99,999 for Class B share purchases or $999,999 for Class C share purchases, you will not be able to purchase Class B or Class C shares, as applicable. For the purpose of determining your total account value, existing accounts for all share classes held with the MFS funds that are linked under a LOI or ROA will be included.

The fund or its agents may at their discretion accept a purchase request for Class B shares or Class C shares that would otherwise exceed the total account value limitation of $99,999 and $999,999, respectively, under certain circumstances, including, but not limited to, purchases by certain types of group retirement plans sponsored or serviced by MFS or an affiliate.

You may have your financial intermediary process your subsequent purchases or you may contact MFS directly. Generally, there is no minimum for subsequent investments except there is generally a $50 minimum for subsequent investments by check and through automatic exchange plans.

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Additional Purchases Directly Through MFSC.

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By Mail. You may purchase additional shares by mailing a check with the returnable portion of your statement to MFSC.

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By Telephone. You may purchase additional shares by transferring money by phone from your pre-designated bank account. You must elect this privilege on your account application or service application.

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Electronically. You may purchase additional shares from a pre-designated bank account via the Internet at mfs.com (MFS Access). You must elect this privilege on your account application or service application and establish a personal identification number (PIN) on MFS Access to use this service.

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By Wire. To purchase additional shares by wire, call MFSC for instructions.

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Automatic Investment Plan. You may purchase additional shares by automatically investing a designated amount from your checking or savings account on any day of the month. You must elect this privilege on your account application or service application.

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Additional Purchases Through Your Financial Intermediary. You can have your financial intermediary purchase shares on your behalf. Your financial intermediary will be responsible for furnishing all necessary documents to MFSC and may charge you for this service.

How to Redeem Shares

Your shares will be sold at the net asset value per share next calculated after your redemption order is received in proper form, minus any applicable CDSC. Your financial intermediary is responsible for transmitting your redemption order to the fund in proper form and in a timely manner. MFSC reserves the right to reject any redemption request that is not in proper form. The specific requirements for proper form depend on the type of account and transaction and the method of redemption; contact MFSC if you have questions about your particular circumstances. A redemption order in an amount less than or equal to the value of your account (other than an exchange) is considered to be in proper form only with respect to shares in your account for which payment has been received and collected. A new redemption order must be submitted if you wish to redeem your shares for which payment had not been received and collected at the time the prior redemption order was received by the fund. Receiving and collecting payment can take up to seven days after a purchase. In certain circumstances, you may need to have your signature guaranteed and/or submit additional documentation to redeem your shares. In general, no signature guarantee is required for a redemption order for up to $100,000 that is signed by all owners or fiduciaries identified in the account registration, paid as registered, and mailed to the address of record.

The fund normally sends out your redemption proceeds within seven days after your request is received in proper form. Under unusual circumstances, such as when the New York Stock Exchange is closed, trading on the Exchange is restricted, or as permitted by the SEC, the fund may suspend redemptions or postpone payment for more than seven days.

You may redeem your shares either by having your financial intermediary process your redemption or by contacting MFSC directly.

Redeeming Directly Through MFSC.

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By Mail. To redeem shares by mail, you can send a letter to MFSC with the name of the fund, your account number, and the number of shares or dollar amount to be redeemed.

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By Telephone. If a signature guarantee is not required, you can call MFSC to have shares redeemed from your account and proceeds mailed to the address of record on the account. You can also call MFSC to have shares redeemed from your account and the proceeds wired directly to a pre-designated bank account. You must elect this privilege on your account application or service application if you wish to have proceeds wired to your bank account.

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Electronically. You can have shares redeemed from your account and the proceeds wired directly to a pre-designated bank account via the Internet at mfs.com (MFS Access). You must elect this privilege on your account application or service application and establish a personal identification number (PIN) on MFS Access to use this service.

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Systematic Withdrawal Plan. For Class A, Class B, and Class C shares, you may elect to automatically receive (or designate someone else to receive) regular periodic payments through an automatic redemption of such classes. Please contact MFSC for details.

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Checkwriting. You may redeem your Class A and Class C shares by writing checks against your account. There is no charge for this service. You must elect this privilege on your account application to use this service. Shares in your account equal in value to the amount of the check plus the applicable CDSC (if any) and any income tax required to be withheld (if any), are redeemed to cover the amount of the check. If your account value is not great enough to cover these amounts, your check will be dishonored. Checkwriting may not be available for all accounts.

Redeeming Through Your Financial Intermediary. You can have your financial intermediary process a redemption on your behalf. Your financial intermediary will be responsible for furnishing all necessary documents to MFSC and may charge you for this service.

Signature Guarantee/Additional Documentation. If a signature guarantee is required, your signature may be guaranteed by an eligible bank, broker/dealer, credit union, national securities exchange, registered securities association, clearing agency, or savings association. MFSC may require additional documentation for certain types of registrations and under certain circumstances. Signature guarantees and this additional documentation shall be accepted in accordance with policies established by MFSC, and MFSC may, at its discretion, make certain exceptions to these requirements. Please contact MFSC with any questions and for the requirements for your particular situation.

Share Certificates. If certificates are outstanding for your shares, you may only redeem such shares by mailing the certificates to MFSC. Telephone, electronic, and systematic withdrawal plan redemptions and checkwriting are not available if certificates are outstanding for your shares.

Redemptions In Kind. If, during any 90-day period, you redeem shares in an amount greater than the lesser of $250,000 or 1% of fund net assets, the fund has the right to pay the redemption amount above such threshold by a distribution in-kind of portfolio securities (redemption in kind). In the event that the fund makes a redemption in kind, you should expect to incur brokerage and other transaction charges when converting the securities to cash, and the securities may increase or decrease in value before you sell them.

Involuntary Redemptions. Because it is costly to maintain small accounts, the MFS funds have reserved the right to redeem your shares without your permission when your account contains less than $500 due to your redemptions or exchanges. Before the fund makes such a redemption, you will be notified and given 60 days to increase your investment to at least $500.

In addition, the MFS funds have reserved the right to redeem your shares without your permission in cases of threatening conduct or suspicious, fraudulent, or illegal activity. Any applicable CDSC will be assessed upon redemption of your shares.

How to Exchange Shares

An exchange involves the redemption of shares of one fund and the purchase of shares of another fund.

Exchange Privilege. You can exchange your shares for shares of the same class of most other MFS funds by having your financial intermediary process your exchange request or by contacting MFSC directly.

You can exchange your Class A shares for shares of the MFS Money Market Fund or the MFS Government Money Market Fund.

The MFS funds allow certain financial intermediaries to place exchange orders on behalf of a group of their discretionary investment advisory clients (“group exchange orders”). As with any exchange request, the funds and their agents reserve the right to reject any group exchange order, and the funds’ agents will generally reject any group exchange order received by the funds or their agents after 1 p.m., Eastern time. In addition, MFD has agreements with certain financial intermediaries which set forth the terms and conditions under which group exchange orders may be placed by these financial intermediaries. These conditions may be more restrictive than those applicable to individual exchange orders, and may include the requirement to provide the funds or their agents with advance notice of group exchange orders.

The minimum exchange amount is generally $1,000 (generally $50 for exchanges made under the automatic exchange plan) or all the shares in an account. MFSC waives or lowers the minimum exchange amount for certain types of investors and investments.

Shares otherwise subject to a CDSC will not be charged a CDSC in an exchange. Shares will retain the CDSC schedule in effect based upon a pro rata share of the CDSC from the exchanged fund and the original purchase date of the shares subject to the CDSC.

Other funds may have different exchange restrictions. You should read the prospectus of the MFS fund into which you are exchanging and consider the differences in objectives, policies, and risks before making any exchange. The exchange privilege may be changed or discontinued at any time, and all exchanges are subject to certain limitations and MFS funds’ policies concerning excessive trading practices, which are designed to protect the funds and their shareholders from the harmful effects of frequent trading.

Other Considerations

Frequent Trading

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Right to Reject or Restrict Purchase and Exchange Orders. The Board of Trustees of the MFS funds has adopted the purchase and exchange limitation policies described below, which it believes are reasonably designed to discourage frequent fund share transactions. MFSC seeks to monitor and enforce these policies, subject to oversight by the Board of Trustees. The MFS funds may alter their policies at any time without notice to shareholders.

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General Purchase and Exchange Limitation Policies. The MFS funds reserve the right to restrict, reject, or cancel (with respect to cancellations, within one business day of the order), without any prior notice, any purchase or exchange order, including transactions believed to represent frequent trading activity. For example, MFSC may in its discretion restrict, reject, or cancel a purchase or exchange order even if the transaction is not subject to specific exchange or other limitations described in this prospectus if MFSC determines that accepting the order could interfere with the efficient management of a fund’s portfolio, increase costs to the fund, dilute the value of an investment in the fund to long-term shareholders, or otherwise not be in the fund’s best interests. In the event that MFSC rejects or cancels an exchange request, neither the redemption nor the purchase side of the exchange will be processed. Each MFS fund reserves the right to delay for one business day the processing of exchange requests in the event that, in MFSC’s judgment, such delay would be in the fund’s best interest, in which case both the redemption and purchase side of the exchange will receive the fund’s net asset values at the conclusion of the delay period.

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Specific Purchase and Exchange Limitation Policies. Under the MFS Funds’ purchase and exchange limitation policy, MFSC will generally restrict, reject or cancel purchase and exchange orders into an MFS fund if MFSC determines that an accountholder has made two exchanges, each in an amount of $5,000 or more, out of an account in such MFS fund during a calendar quarter (“two exchange limit”). This policy does not apply to MFS money market funds or exchanges initiated by a retirement plan trustee or sponsor rather than by a plan participant, and other similar non-discretionary exchanges (e.g., in connection with fund mergers/acquisitions/ liquidations).

considers the information available to it at the time and reserves the right to consider trading multiple accounts under common ownership, control, or influence to be trading out of a single account.

Exchanges made on the same day in the same account are aggregated for purposes of counting the number and dollar amount of exchanges made by the accountholder (e.g., a shareholder who on the same day exchanges $6,000 from one MFS fund into two other MFS funds, by exchanging $3,000 into each of the two MFS funds, will be viewed as having made one exchange transaction exceeding $5,000 in value).

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Financial Intermediary Purchase and Exchange Limitations. MFSC receives purchase, exchange and redemption orders through financial intermediaries. A financial intermediary’s policy restricting frequent trading may be more or less restrictive than the MFS funds’ policies, may permit certain transactions not permitted by the MFS funds’ policies, or prohibit transactions not subject to the MFS funds’ policies. You should consult your financial intermediary regarding the application of these limitations and whether your financial intermediary imposes any additional or different limitations.

MFSC believes that financial intermediaries are required to enforce the terms of the prospectus for each MFS fund for which they maintain an omnibus account with MFSC, including the MFS funds’ frequent trading policies. However, there is no assurance that each financial intermediary enforces the specific and/or general purchase and exchange limitations of the MFS funds’ frequent trading policies.

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Omnibus Accounts. MFSC receives purchase, exchange, and redemption orders through certain financial intermediaries that hold omnibus accounts with an MFS fund. Omnibus account arrangements are common forms of holding shares of MFS funds, particularly among certain financial intermediaries such as brokers, retirement and 529 plans, investment advisors, and insurance companies. MFSC is generally not able to identify trading by a particular underlying shareholder within an omnibus account, which makes it difficult or impossible to determine if a particular underlying shareholder has violated the two exchange limit or is otherwise engaged in frequent trading.

In circumstances where shareholders hold shares through financial intermediaries, the MFS funds may rely upon the financial intermediary’s policy to restrict frequent trading and its monitoring of such policy in lieu of the MFS funds’ two-exchange limit if MFSC determines that the financial intermediary’s policy is reasonably designed to identify and curtail trading activity that is not in the best interest of the funds (“Adopted Financial Intermediary Policy”). If MFSC is relying on an Adopted Financial Intermediary Policy, MFSC will not typically request underlying shareholder data but will rely on the financial intermediary to monitor trading activity in good faith in accordance with its policy. In other circumstances where shareholders hold shares through a financial intermediary that does not enforce the MFS funds’ frequent trading policies and does not have its own policy to restrict frequent trading that MFSC determines is reasonably designed to identify and curtail trading activity that is not in the best interests if the funds (a “Non Adopted Policy”), MFSC may rely upon the financial intermediary to enforce its Non Adopted Policy (if any). MFSC expects to request underlying shareholder data from financial intermediaries with Non Adopted Policies more frequently than from financial intermediaries with Adopted Financial Intermediary Policies.

For omnibus accounts for which MFSC does not regularly receive underlying shareholder data, MFSC reviews trading activity at the omnibus level to detect suspicious trading activity. This review is based on MFSC’s internal parameters for detecting frequent trading, including reviewing transactions that exceed a certain dollar amount or transactions that occur close in time to other transactions in the same account or in multiple accounts that are under common ownership or influence. These parameters may change from time to time. If MFSC detects suspicious trading activity at the omnibus level it will contact the financial intermediary to request underlying shareholder level activity to determine whether there is underlying shareholder level frequent trading. MFSC will ordinarily review such data to detect suspicious trading activity and not to determine whether there have been violations of the two exchange limit. If frequent trading is identified, MFSC will take appropriate action, such as prohibiting purchases into the account, requiring purchases by mail, or prohibiting purchases from the financial intermediary.

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Limitations on the Ability to Detect and Curtail Frequent Trading Practices. Depending upon the composition of a fund’s shareholder accounts and the efforts made by certain shareholders to evade these limitations, MFSC may not be in a position to monitor and deter frequent trading with respect to a significant percentage of a fund’s shareholders. MFSC’s ability to monitor and deter frequent trading in omnibus accounts ultimately depends on the capability and cooperation of the financial intermediary and the frequency with which MFSC requests underlying shareholder account data from omnibus accounts. In certain instances, a financial intermediary may be unable to provide MFSC with information about underlying shareholder level activity. There is no assurance that MFSC will request data with sufficient frequency to detect or deter frequent trading in omnibus accounts effectively. Shareholders seeking to engage in frequent trading practices may deploy a variety of strategies to avoid detection, and, despite the efforts of MFSC to prevent frequent trading, there is no assurance that MFSC will be able to identify such shareholders or curtail their trading practices.

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Frequent Trading Risks. To the extent that the MFS funds or their agents are unable to curtail excessive trading practices in a fund, these practices may interfere with the efficient management of the fund’s portfolio, may result in increased transaction and administrative costs, and may adversely impact the fund’s performance.

To the extent that the fund invests in securities that trade infrequently or are difficult to value, such as the securities of smaller companies, high yield debt instruments, and floating rate loans, the interests of long-term shareholders may be diluted as a result of price arbitrage, a short-term trading strategy that seeks to exploit perceived pricing inefficiencies in the fund’s investments. Such short-term trading strategies may interfere with efficient management of the fund’s portfolio to a greater degree than funds that invest in more frequently traded or liquid securities, in part because the fund may have difficulty selling these portfolio securities at advantageous times or prices to satisfy large and/or frequent redemption requests. Any successful price arbitrage may also cause dilution in the value of fund shares held by other shareholders.

Unauthorized Transactions. MFS will not be responsible for losses that result from unauthorized transactions unless MFSC does not follow procedures reasonably designed to verify your identity. If an account has more than one owner or authorized person, MFSC will accept telephone and online instructions from any one owner or authorized person. It is important that you contact MFSC immediately about any transactions you believe to be unauthorized.

Ability to contact MFSC. Certain methods of contacting MFSC, such as by mail, telephone, or electronically, may be unavailable or delayed (for example, after natural disasters or during periods of significant/major political, social, or economic instability).

Reservation of Other Rights. In addition to the rights expressly stated elsewhere in this prospectus, MFSC reserves the right to: 1) alter, add, or discontinue any conditions of purchase, service, or privilege at any time without notice; and 2) freeze any account or suspend account services when MFSC has received reasonable notice (written or otherwise) of a dispute between registered or beneficial account owners or when MFSC believes a fraudulent transaction may occur or has occurred.

Anti-Money Laundering Restrictions. Federal law requires the fund to implement policies and procedures reasonably designed to prevent, detect and report money laundering and other illegal activity. The fund, consistent with applicable federal law, may redeem your shares and close your account; suspend, restrict or cancel purchase and redemption orders; process redemption requests and withhold your proceeds; and take other action if it is unable to verify your identity within a reasonable time or conduct required due diligence on your account or as otherwise permitted by its anti-money laundering policies and procedures. Any applicable CDSC will be assessed upon redemption of your shares.

Confirmations in Quarterly Statements. Transactions made under certain periodic investment and withdrawal programs (including reinvestment plans) will be confirmed on quarterly account statements.

OTHER INFORMATION

Valuation

The price of each class of the fund’s shares is based on its net asset value. The net asset value of each class of shares is determined each day the New York Stock Exchange (the Exchange) is open for trading as of the close of regular trading on the Exchange (generally 4:00 p.m. Eastern time). However, net asset value may be calculated earlier in emergency situations or as otherwise permitted by the SEC. Net asset value per share is computed by dividing the net assets allocated to each share class by the number of shares outstanding for that class. On days when the Exchange is closed (such as week-ends and holidays), net asset value is not calculated, and the fund does not transact purchase and redemption orders. To the extent the fund’s assets are traded in other markets on days when the fund does not price its shares, the value of the fund’s assets may change when you will not be able to purchase or redeem shares.

To determine net asset value, the fund’s investments for which reliable market quotations are readily available are valued at market value. Certain short term debt instruments are valued at amortized cost.

The Board of Trustees has delegated primary responsibility for determining or causing to be determined the value of the fund’s investments (including any fair valuation) to the adviser pursuant to valuation policies and procedures approved by the Board. If the adviser determines that reliable market quotations are not readily available, investments are valued at fair value as determined in good faith by the adviser in accordance with such procedures under the oversight of the Board of Trustees.

Under the fund’s valuation policies and procedures, market quotations are not considered to be readily available for most types of debt instruments and floating rate loans and many types of derivatives. These investments are generally valued at fair value based on information from independent pricing services. These valuations can be based on both dealer-supplied valuations and electronic data processing techniques, which take into account factors such as institutional-size trading in similar groups of securities, yield, quality, coupon rate, maturity, type of issue, trading characteristics, and other market data.

In addition, investments may be valued at fair value if the adviser determines that an investment’s value has been materially affected by events occurring after the close of the exchange or market on which the investment is principally traded (such as a foreign exchange or market) and prior to the determination of the fund’s net asset value, or after the halting of trading of a specific security where trading does not resume prior to the close of the exchange or market on which the security is principally traded. The adviser may rely on independent pricing services or other information (such as the correlation with price movements of similar securities in the same or other markets; the type, cost and investment characteristics of the security; the business and financial condition of the issuer; and trading and other market data) to assist in determining whether to fair value and at what value to fair value an investment. The value of an investment for purposes of calculating the fund’s net asset value can differ depending on the source and method used to determine value. When fair valuation is used, the value of an investment used to determine the fund’s net asset value may differ from quoted or published prices for the same investments. There can be no assurance that the fund could obtain the fair value assigned to an investment if it were to sell the investment at the same time at which the fund determines its net asset value per share.

Distributions

The fund intends to declare a dividend daily and to pay these dividends to shareholders at least monthly.

Any capital gains are distributed at least annually.

Distribution Options

The following distribution options are generally available:

•

Dividend and capital gain distributions reinvested in additional shares (this option will be assigned if no other option is specified);

•

Dividend distributions in cash; capital gain distributions reinvested in additional shares;

•

Dividend and capital gain distributions in cash; or

•

Dividend and capital gain distributions reinvested into the same class of shares of another MFS Fund.

The distribution option for accounts with dividend distributions of less than $10 will generally be changed to reinvestment in additional shares of the

fund. If you have elected to receive distributions in cash, and the postal service is unable to deliver checks to your address of record, or you do not respond to mailings from MFSC with regard to uncashed distribution checks, your distribution option may be converted to having all distributions reinvested in additional shares. You should contact MFSC to change your distribution option, and your request to do so must be received by MFSC before the record date for a distribution in order to be effective for that distribution. No interest will accrue on amounts represented by uncashed distribution checks.

Tax Considerations

The following discussion is very general. You are urged to consult your tax adviser regarding the effect that an investment in the fund may have on your particular tax situation, including possible foreign, state, and local taxes. Also, this discussion does not apply to shares of the fund held through tax-exempt retirement plans.

The fund expects to distribute substantially all of its income and gains annually. You may receive three different types of distributions from the fund: exempt-interest dividends; ordinary dividends; and capital gain dividends. Most distributions will be exempt-interest dividends, which are exempt from federal income tax. Ordinary dividends are normally subject to federal income tax at ordinary income tax rates. (The fund does not expect any distributions to be treated as qualified dividend income, which is taxed at reduced rates.) Distributions designated as capital gain dividends are taxable as long-term capital gains. Any taxes that you pay on a distribution will be the same whether you take the distribution in cash or have it reinvested in additional shares of the fund. If you buy shares when a fund has realized but not yet distributed ordinary income or capital gains, you will pay full price for the shares and then receive a portion back as a taxable distribution.

Any gain resulting from the sale or exchange of your shares will generally also be subject to tax.

The fund’s investments in certain debt instruments may cause the fund to recognize income in excess of the cash generated by such instruments. Thus, the fund could be required at times to liquidate other investments in order to satisfy its distribution requirements.

If you receive social security or railroad retirement benefits, you should consult your tax adviser to determine what effect, if any, an investment in the fund may have on the federal taxation of your benefits. In addition, an investment in the fund may result in liability for federal alternative minimum tax, for both individual and corporate shareholders.

Long-term capital gain rates applicable to most individuals have been temporarily reduced for taxable years beginning before January 1, 2011.

The Form 1099 that is mailed to you every January details your distributions and how they are treated for federal tax purposes.

Provision of Annual and Semiannual Reports and Prospectuses

The fund produces financial reports every six months and updates its prospectus annually. To avoid sending duplicate copies of materials to households, only one copy of the fund’s annual and semiannual report and prospectus will be mailed to shareholders having the same residential address on the fund’s records. However, any shareholder may contact MFSC (please see back cover for address and telephone number) to request that copies of these reports and prospectuses be sent personally to that shareholder.

FINANCIAL HIGHLIGHTS

The financial highlights are intended to help you understand a fund’s financial performance for the past five years (or, if shorter, the period of the fund’s operation). Certain information reflects financial results for a single fund share. The total returns in the financial highlights represent the rate by which an investor would have earned (or lost) on an investment in a fund (assuming reinvestment of all distributions) held for the entire period. This information has been audited by the fund’s independent registered public accounting firm, whose report, together with the fund’s financial statements, are included in the fund’s Annual Report to shareholders. The fund’s Annual Report is available upon request by contacting MFS Service Center, Inc. (please see back cover for address and telephone number). The financial statements contained in the Annual Report are incorporated by reference into the SAI. The fund’s independent registered public accounting firm is Deloitte & Touche LLP.


	Years Ended 3/31
	2008			2007			2006			2005			2004
Class A
Net asset value, beginning of period	$	8.55		$	8.53		$	8.58		$	8.70		$	8.54

Income (loss) from investment operations
Net investment income (d)	$	0.42		$	0.42	(z)	$	0.41		$	0.42		$	0.41
Net realized and unrealized gain (loss) on investments		(0.35	)		0.00	(w)(z)		(0.06	)		(0.13	)		0.17

Total from investment operations	$	0.07		$	0.42		$	0.35		$	0.29		$	0.58

Less distributions declared to shareholders
From net investment income	$	(0.40	)	$	(0.40	)	$	(0.40	)	$	(0.41	)	$	(0.42	)
From net realized gain on investments		(0.01	)		—			—			—			—

Total distributions declared to shareholders	$	(0.41	)	$	(0.40	)	$	(0.40	)	$	(0.41	)	$	(0.42	)

Net asset value, end of period	$	8.21		$	8.55		$	8.53		$	8.58		$	8.70

Total return (%) (r)(s)(t)		0.81			5.00			4.18			3.49			6.94

Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		1.05			1.19			1.17			1.04			1.04
Expenses after expense reductions (f)		0.80			0.94			0.92			0.79			0.88
Expenses after expense reductions and excluding interest expense and fees (f)(l)		0.70			0.79			0.81			0.79			0.88
Net investment income		4.99			4.91	(z)		4.71			4.90			4.80
Portfolio turnover		32			10			9			8			9
Net assets at end of period (000 omitted)	$	279,614		$	248,226		$	240,212		$	241,850		$	264,797


	Years Ended 3/31
	2008			2007			2006			2005			2004
Class B
Net asset value, beginning of period	$	8.57		$	8.54		$	8.59		$	8.72		$	8.55

Income (loss) from investment operations
Net investment income (d)	$	0.36		$	0.36	(z)	$	0.34		$	0.36		$	0.35
Net realized and unrealized gain (loss) on investments		(0.36	)		0.00	(w)(z)		(0.05	)		(0.14	)		0.18

Total from investment operations	$	0.00	(w)	$	0.36		$	0.29		$	0.22		$	0.53

Less distributions declared to shareholders
From net investment income	$	(0.34	)	$	(0.33	)	$	(0.34	)	$	(0.35	)	$	(0.36	)
From net realized gain on investments		(0.01	)		—			—			—			—

Total distributions declared to shareholders	$	(0.35	)	$	(0.33	)	$	(0.34	)	$	(0.35	)	$	(0.36	)

Net asset value, end of period	$	8.22		$	8.57		$	8.54		$	8.59		$	8.72

Total return (%) (r)(s)(t)		(0.06	)		4.34			3.40			2.60			6.27

Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		1.80			1.95			1.92			1.79			1.79
Expenses after expense reductions (f)		1.55			1.70			1.67			1.54			1.63
Expenses after expense reductions and excluding interest expense and fees (f)(l)		1.45			1.55			1.56			1.54			1.63
Net investment income		4.24			4.16	(z)		3.96			4.15			4.05
Portfolio turnover		32			10			9			8			9
Net assets at end of period (000 omitted)	$	22,372		$	26,919		$	36,752		$	43,930		$	52,594


	Years Ended 3/31
	2008			2007			2006			2005			2004
Class C
Net asset value, beginning of period	$	8.59		$	8.56		$	8.61		$	8.73		$	8.56

Income (loss) from investment operations
Net investment income (d)	$	0.35		$	0.36	(z)	$	0.35		$	0.36		$	0.35
Net realized and unrealized gain (loss) on investments		(0.35	)		0.01	(z)		(0.06	)		(0.13	)		0.18

Total from investment operations	$	0.00	(w)	$	0.37		$	0.29		$	0.23		$	0.53

Less distributions declared to shareholders
From net investment income	$	(0.34	)	$	(0.34	)	$	(0.34	)	$	(0.35	)	$	(0.36	)
From net realized gain on investments		(0.01	)		—			—			—			—

Total distributions declared to shareholders	$	(0.35	)	$	(0.34	)	$	(0.34	)	$	(0.35	)	$	(0.36	)

Net asset value, end of period	$	8.24		$	8.59		$	8.56		$	8.61		$	8.73

Total return (%) (r)(s)(t)		(0.05	)		4.34			3.41			2.72			6.27

Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		1.80			1.94			1.92			1.79			1.79
Expenses after expense reductions (f)		1.55			1.69			1.67			1.54			1.63
Expenses after expense reductions and excluding interest expense and fees (f)(l)		1.45			1.54			1.56			1.54			1.63
Net investment income		4.23			4.16	(z)		4.09			4.15			4.05
Portfolio turnover		32			10			9			8			9
Net assets at end of period (000 omitted)	$	42,759		$	35,070		$	34,618		$	33,911		$	37,508

Any redemption fees charged by the fund during the 2005 fiscal year resulted in a per share impact of less than $0.01.

(d)	Per share data are based on average shares outstanding.

(f)	Ratios do not reflect reductions from fees paid indirectly, if applicable.

(l)	Interest expense and fees relate to payments made to the holder of the floating rate certificate from trust assets.

(r)	Certain expenses have been reduced without which performance would have been lower.

(s)	From time to time the fund may receive proceeds from litigation settlements, without which performance would be lower.

(t)	Total returns do not include any applicable sales charges.

(w)	Per share amount was less than $0.01.

(z)

The fund applied a change in estimate for amortization of premium on certain debt securities in the year ended March 31, 2007 that resulted in an increase of $0.03 per share to net investment income, a decrease of $0.03 per share to net realized and unrealized gain (loss) on investments, and an increase of 0.30% to the net investment income ratio for Class A, Class B, and Class C. The change in estimate had no impact on net assets, net asset value per share or total return of the class.

MFS Municipal Income Fund

Shareholder Communications with the Board of Trustees. The Board of Trustees of the MFS funds has adopted procedures by which shareholders may send communications to the Board. Shareholders may mail written communications to the Board to the attention of the Board of Trustees, [fund name], Massachusetts Financial Services Company, 500 Boylston Street, Boston, MA 02116-3741, Attention: Frank Tarantino, Independent Chief Compliance Officer of the Fund. Shareholder communications must (i) be in writing and be signed by the shareholder, (ii) identify the MFS fund to which they relate and (iii) identify the class and number of shares held by the shareholder.

If you want more information about MFS Municipal Income Fund, the following documents are available free upon request:

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

Statement of Additional Information (SAI). The SAI, dated August 1, 2008, provides more detailed information about the fund 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 fund, and make inquiries about the fund, by contacting:

MFS Service Center, Inc.

500 Boylston Street

Boston, MA 02116-3741

Telephone: 1-800-225-2606

Internet: mfs.com

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

Public Reference Room

Securities and Exchange Commission

100 F Street, NE

Washington, D.C., 20549-0102

Information on the operation of the Public Reference Room may be obtained by calling the Commission at 1-202-551-8090. Reports and other information about the fund are available on the Edgar Database on the Commission’s Internet Web site at http://www.sec.gov, and copies of this information may be obtained, upon payment of a duplicating fee, by electronic request at the following e-mail address: publicinfo@sec.gov or by writing the Public Reference Section at the above address.

The fund’s Investment Company Act file number is 811-4096.

Class A1 Shares

Class B1 Shares

MFS^® Municipal Income Fund

Prospectus August 1, 2008


RISK RETURN SUMMARY		1
EXPENSE SUMMARY		10
MANAGEMENT OF THE FUND		13
DESCRIPTION OF SHARE CLASSES		17
HOW TO PURCHASE, REDEEM, AND EXCHANGE SHARES		27
OTHER INFORMATION		39
FINANCIAL HIGHLIGHTS		43

RISK RETURN SUMMARY

Investment Objective

Principal Investment Strategies

MFS (Massachusetts Financial Services Company, the fund's investment adviser) normally invests the fund’s assets primarily in municipal instruments.

MFS primarily invests the fund’s assets in investment grade debt instruments, but may also invest in lower quality debt instruments.

MFS may invest 25% or more of the fund’s total assets in municipal instruments that finance similar projects, such as those relating to education, healthcare, housing, utilities, water, or sewers.

MFS may engage in active and frequent trading in pursuing the fund's principal investment strategies.

In response to market, economic, political, or other conditions, MFS may depart from the fund’s principal investment strategies by temporarily investing for defensive purposes.

Principal Investment Types

Derivatives: Derivatives are financial instruments whose value is based on the value of one or more underlying indicators or the difference between

underlying indicators. Underlying indicators may include a security or other financial instrument, asset, currency, interest rate, credit rating, commodity, volatility measure, or index. Derivatives often involve a counterparty to the transaction. Derivatives include futures, forward contracts, options, structured securities, inverse floating rate instruments, swaps, caps, floors, and collars.

Principal Risks

The principal risks of investing in the fund are:

other geopolitical events can have a dramatic adverse effect on the value of a debt instrument. For certain types of instruments, including derivatives, the value of the instrument depends in part on the credit quality of the counterparty to the transaction. For other types of debt instruments, including collateralized instruments, the price of the debt instrument also depends on the credit quality and adequacy of the underlying assets or collateral. Enforcing rights against the underlying assets or collateral may be difficult, or the underlying assets or collateral may be insufficient, if the issuer defaults.

difficult to predict and the potential impact of prepayment on the price of a debt instrument depends on the terms of the instrument and can result in significant volatility.

Municipal Market Risk: The price of municipal instruments can be volatile and significantly affected by adverse tax or court rulings, legislative or political changes, and the financial developments of municipal issuers. Because many municipal instruments are issued to finance similar projects, especially those relating to education, health care, housing, utilities, and water and sewer, conditions in these industries can affect the overall municipal market. In addition, changes in the financial condition of an individual municipal insurer can affect the overall municipal market.

Counterparty and Third Party Risk: Transactions involving a counterparty other than the issuer of the instrument, or a third party

responsible for servicing the instrument, are subject to the credit risk of the counterparty or third party, and to the counterparty’s or third party’s ability to perform in accordance with the terms of the transaction.

Further Information Available

Bar Chart and Performance Table

•

how the fund’s performance over time compares with that of a broad measure of market performance, and

•

returns before the deduction of taxes and returns after the deduction of certain taxes for Class A shares.

The chart and table provide past performance information. The fund’s past performance (before and after taxes) does not necessarily indicate how the fund will perform in the future. Because the fund’s Class A1 and Class B1 shares were initially offered on June 22, 2007, these classes do not have a performance record to report. As a result, the bar chart and the performance table show performance of the fund’s Class A shares, which are offered in a separate prospectus. Although the Class A1, Class B1, and Class A shares would have similar annual returns (because they represent interests in the same portfolio of securities), Class A1, Class B1, and Class A performance would differ to the extent that Class A1 and Class B1 have lower or higher expenses than Class A.

The performance information in the chart and table is based upon calendar year periods, while the performance information presented under the caption “Financial Highlights” and in the fund’s shareholder reports is based upon the fund’s fiscal year. Therefore, these performance results may differ.

Bar Chart. The bar chart shows changes over time in the annual total return of the fund’s Class A shares for the past ten calendar years, and assumes the reinvestment of distributions. The chart and related notes do not take into account any sales charges (loads) that you may be required to pay upon purchase or redemption of the fund’s shares. If these sales charges were included, they would reduce the returns shown. The return of the fund’s other classes of shares will differ from the Class A share returns shown in the bar chart, depending upon the expenses of those classes.

LOGO

Performance Table. This table shows how the average annual total returns of Class A shares of the fund, before the deduction of taxes (‘‘Returns Before Taxes’’), compare to a broad measure of market performance, and assumes the deduction of the maximum applicable sales loads (initial sales charge and/or contingent deferred sales charge (CDSC), as applicable), and the reinvestment of distributions. In addition, for Class A shares, this table shows Class A average annual total returns:

•

after the deduction of taxes on distributions made on Class A shares, such as capital gains and income distributions (‘‘Class A Shares’ Return After Taxes on Distributions’’), and

•

after the deduction of taxes on both distributions made on Class A shares and on redemption of Class A shares, assuming that the shares are redeemed at the end of the periods for which returns are shown (‘‘Class A Shares’ Return After Taxes on Distributions and Sale of Class A Shares’’).

Average Annual Total Returns (for the Periods Ended December 31, 2007)


Share Class	1 Year		5 Years		10 Years
Returns Before Taxes
A Shares, With Initial Sales Charge (4.75%)	(2.26	)%	3.44	%	4.09	%
Returns After Taxes (Class A Shares Only)
A Shares’ Return After Taxes on Distributions, with Initial Sales Charge (4.75%)	(2.28	)%	3.44	%	4.06	%
A Shares’ Return After Taxes on Distributions and Sale of Class A Shares, with Initial Sales Charge (4.75%)	0.14	%	3.63	%	4.19	%
Benchmark Comparison (Returns Before Taxes)
Lehman Brothers Municipal Bond Index*†	3.36	%	4.30	%	5.17	%

*	The Lehman Brothers Municipal Bond Index is a market capitalization-weighted index that measures the performance of the tax-exempt bond market.

†	Source: FactSet Research Systems Inc.

All performance results reflect any applicable fee and expense waivers in effect during the periods shown; without these, the results would have been lower.

The fund commenced investment operations on December 29, 1986, with the offering of Class B shares, and subsequently offered Class A shares on September 7, 1993, Class C shares on January 3, 1994, and Class A1 and Class B1 shares on a limited basis on June 22, 2007.

EXPENSE SUMMARY

Expense Table

This table describes the fees and expenses that you may pay when you buy, redeem, and hold shares of the fund. The annual fund operating expenses are based on expenses incurred during the fund’s most recently completed fiscal year adjusted to reflect annualized expenses and the management fee set forth in the fund’s Investment Advisory Agreement. The fund’s annual operating expenses may vary in future years.

Shareholder Fees (fees paid directly from your investment):


Share Class	A1		B1
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	4.75	%	N/A
Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less)	N/A		4.00	%

Annual Fund Operating Expenses (expenses that are deducted from fund assets):


Management Fees	0.40	%	0.40	%
Distribution and/or Service (12b-1) Fees⁽¹⁾	N/A		0.76	%
Other Expenses⁽²⁾	0.24	%	0.24	%

Total Annual Fund Operating Expenses⁽²⁾	0.64	%	1.40	%
Fee Reductions⁽³⁾	(0.05	)%	(0.05	)%

Net Expenses⁽²⁾	0.59	%	1.35	%

A contingent deferred sales charge (referred to as a CDSC) of 1% may be deducted from your redemption proceeds if you buy $1 million or more of Class A1 shares and you redeem your investment within 12 months of your purchase if you purchased shares prior to September 1, 2008, and within 24 months of your purchase if you purchased shares on or after September 1, 2008.

(1)

The fund’s Rule 12b-1 plan permits it to pay distribution and/or service fees to support the sale and distribution of the fund’s Class B1 shares and the services provided by financial intermediaries. The maximum rates that may be charged under the plan, together with details of any fee reduction arrangements, are set forth under “Distribution and Service Fees.”

(2)

The fund has entered into an expense offset arrangement that reduces the fund’s custodian fee based upon the amount of cash maintained by the fund with its custodian. Such fee reduction is not reflected in the table. Had this fee reduction been taken into account, “Net Expenses” would be lower. “Other Expenses” also include certain interest expense and fees in the amount of 0.09% related to the fund’s investments in inverse floating rate investments. Under accounting rules, the fund recognizes additional income

in an amount equal to these expenses. Therefore, the fund’s net asset values per share and performance have not been affected by these expenses. However, these expenses are included in the fund’s “Total Annual Fund Operating Expenses” and “Net Expenses” in the table above, and in the “Example of Expenses” below. Had these expenses and fees not been included, “Net Expenses” would have been 0.50% for Class A1 shares and 1.26% for Class B1 shares.

(3)

MFS has agreed in writing to reduce the fund’s management fee to 0.30% annually until February 28, 2009. See “Management of the Fund - Investment Adviser.” Such fee reduction is not reflected in the table. Had this fee reduction been taken into account, “Total Annual Fund Operating Expenses” would have been lower. In addition, MFS has agreed in writing to bear the fund’s expenses such that “Other Expenses,” determined without giving effect to the expense offset arrangement described above, do not exceed 0.10% annually for each of Class A1 shares and Class B1 shares. This written agreement excludes management fees, distribution and service fees, interest, taxes, extraordinary expenses, brokerage and transaction costs, and investment-related expenses (including interest expenses and fees associated with investments in inverse floating rate instruments) and will continue until at least July 31, 2009.

Example of Expenses

These examples are intended to help you compare the cost of investing in the fund with the cost of investing in other mutual funds.

The examples assume that:

•

You invest $10,000 in the fund for the time periods indicated and you redeem your shares at the end of the time periods (unless otherwise indicated);

•

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

•

The fund’s operating expenses remain the same, except that the fund's total operating expenses are assumed to be the fund's “Net Expenses” for the period during which any written fee reductions are in effect (see “Expense Summary - Expense Table” above).

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


Share Class	1 Year		3 Years		5 Years		10 Years
A1 shares	$	60	$	200	$	352	$	794
B1 shares⁽¹⁾
Assuming redemption at end of period	$	537	$	738	$	961	$	1,290
Assuming no redemption	$	137	$	438	$	761	$	1,290

(1)	Class B1 shares convert to Class A1 shares approximately eight years after purchase; therefore, years nine and ten reflect Class A1 expenses.

MANAGEMENT OF THE FUND

Investment Adviser

For the fiscal year ended March 31, 2008, the fund paid MFS an effective management fee equal to 0.30% of the fund’s average daily net assets.

The management fee set forth in the Investment Advisory Agreement is 0.40% annually of the fund’s average daily net assets. MFS has agreed in writing to reduce its management fee to 0.30% annually of the fund’s average daily net assets. MFS has agreed to maintain this management fee reduction until February 28, 2009 as part of its settlement with the New York Attorney General concerning market timing and related matters.

been named as defendants in multiple lawsuits filed in federal and state courts. The various lawsuits that are still pending generally allege that some or all of the defendants permitted or acquiesced in market timing and/or late trading in some of the MFS funds, and inadequately disclosed MFS’ internal policies concerning market timing and such matters. The pending lawsuits assert that some or all of the defendants violated the federal securities laws, including the Securities Act of 1933, the Securities Exchange Act of 1934, the Investment Company Act of 1940, and the Investment Advisers Act of 1940, as well as fiduciary duties and other violations of common law. The pending lawsuits variously have been commenced as class actions or individual actions on behalf of investors who purchased, held, or redeemed shares of the MFS funds during specified periods, or as derivative actions on behalf of the MFS funds.


Information		Approximate Date of Posting to Web Site
Fund’s top 10 securities holdings as of each month’s end		14 days after month end
Fund’s full securities holdings as of each month’s end		24 days after month end

If a fund has substantial investments in both equity and debt instruments, the fund’s top 10 equity holdings and top 10 debt holdings will be made available.

Portfolio Manager(s)


Portfolio Manager	Primary Role	Since	Title and Five Year History
Geoffrey L. Schechter	Portfolio Manager	2000	Investment Officer of MFS; employed in the investment management area of MFS since 1993.

Administrator

Distributor

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

Shareholder Servicing Agent

MFS Service Center, Inc. (‘‘MFSC’’), a wholly owned subsidiary of MFS, provides dividend and distribution disbursing and transfer agent and recordkeeping functions in connection with the issuance, transfer, and redemption of each class of shares of the fund under a Shareholder Servicing Agent Agreement. MFSC receives a fee based on the costs it incurs in providing these services and a target profit margin. In addition, MFSC is reimbursed for payments made to service providers that provide certain sub-accounting and other shareholder services (shareholder servicing payments) and out-of-pocket expenses.

DESCRIPTION OF SHARE CLASSES

The fund offers Class A1 and Class B1 shares through this prospectus. Class A1 and Class B1 shares are available only to shareholder accounts opened in the fund in connection with the fund’s acquisition of all the assets and certain stated liabilities of MFS Municipal Bond Fund pursuant to an agreement and plan of reorganization. Class A1 and Class B1 shareholders of the fund can purchase additional Class A1 and Class B1 shares through accounts opened in connection with the reorganization. However, once a Class A1 or Class B1 shareholder has closed their account in the fund, they will be prohibited from purchasing Class A1 or B1 shares in the future. The fund also offers Class A, Class B, and Class C shares, which are made available through a separate prospectus provided to investors eligible to purchase them.

Sales Charges and Waivers or Reductions

You may be subject to an initial sales charge when you purchase Class A1, or a CDSC when you redeem Class A1 or Class B1 shares. These sales charges are paid to MFD.

In the circumstances described below, you may qualify for a sales charge waiver or reduction for purchases or redemptions of Class A1 or Class B1 shares. In addition, other sales charge waivers or reductions may apply to certain transactions by retirement plans, section 529 tuition programs, and certain other groups (e.g., affiliated persons of MFS) and with respect to certain types of investment programs (e.g., certain wrap accounts or fund supermarket investments). Details regarding the types of investment programs and categories of investors eligible for these waivers or reductions are provided in the SAI, which is available to you free of charge, and on the fund’s Web site at mfs.com. Some of these programs and waivers or reductions may not be available to you if your shares are held through certain types of accounts, such as retirement accounts and 529 plans, or certain accounts that you may have with your financial intermediary. Waivers or reductions may be eliminated, modified, and added at any time without providing advance notice to shareholders.

Class A1 Shares. You may purchase Class A1 shares at the offering price (which includes the applicable initial sales charge). In some cases, you may purchase Class A1 shares without an initial sales charge; in these cases, you will generally be subject to a 1% CDSC upon redemption within 12 months of your purchase.

The amount of the initial sales charge you pay when you buy Class A1 shares differs depending upon the amount you invest, as follows:


	*Initial Sales Charge As Percentage Of:**
Amount of Purchase	Gross Purchase Amount (Offering Price*)		Net Amount Invested
Less than $50,000	4.75	%	4.99	%
$50,000 but less than $100,000	4.25	%	4.44	%
$100,000 but less than $250,000	3.75	%	3.90	%
$250,000 but less than $500,000	2.75	%	2.83	%
$500,000 but less than $1,000,000	2.00	%	2.04	%
$1,000,000 or more	None	**	None	**

*	Offering price is calculated by dividing the net asset value of a share by the difference between 1 and the initial sales charge percentage. Because the offering price is rounded to two decimal places, actual sales charges you pay may be more or less than those calculated using these percentages.

**	A 1% CDSC will generally apply to such purchases.

You pay no initial sales charge when you invest $1 million or more in Class A1 shares. However, for purchasers other than Employer Retirement Plans, a CDSC of 1% will generally be deducted from your redemption proceeds if you redeem within 12 months of your purchase if you purchased shares prior to September 1, 2008, and within 24 months of your purchase if you purchased shares on or after September 1, 2008.

Class B1 Shares. You may purchase Class B1 shares at net asset value without an initial sales charge, but if you redeem your shares within the first six years after purchase, you may be subject to a CDSC (declining from 4% during the first year to 0% after six years).

The CDSC is imposed according to the following schedule:


Year of redemption after purchase	1st		2nd		3rd		4th		5th		6th		7th
Contingent deferred sales charge	4	%	4	%	3	%	3	%	2	%	1	%	0	%

If you hold Class B1 shares for approximately eight years, they will convert to Class A1 shares of the fund. All Class B1 shares you acquire through the reinvestment of dividends and distributions will be held in a separate sub-account. Each time any Class B1 shares in your account convert to Class A1 shares, a proportionate number of the Class B1 shares in the sub-account will also convert to Class A1 shares.


Program	Investments Eligible For:
Program	Waived Initial Sales Charge	Reduced Initial Sales Charge	Waived CDSC
Letter of Intent		X
Right of Accumulation		X
Automatic Exchange Plan	X*
Exchange Privilege	X*
Systematic Withdrawal Plan			X**
Distribution Reinvestment	X
Distribution Investment Program	X
Other Sales Charge Waivers	X		X

*	Investments under the Automatic Exchange Plan or certain other exchanges under the Exchange Privilege may be subject to a sales charge in certain cases.

**	Not available for Class A1 shares and limited for Class B1 shares.

•

Letter Of Intent (LOI). You may pay a reduced or no initial sales charge on purchases of Class A1 shares if you intend to invest a specific dollar amount, based on the gross amount of your investment (including the amount of any sales charge paid), including investments through any linked accounts in any class

of any MFS fund within a 13-month period (36 months for a $1 million commitment). Distributions reinvested in additional shares of the fund or distributions from other MFS funds automatically invested in shares of the fund will not apply toward the satisfaction of the LOI.

For each purchase you make under the LOI you will pay the initial sales charge rate applicable to the total amount you intended to purchase. If, however, you do not purchase the intended amount within the relevant time period, your account will be adjusted by redemption of the amount of shares needed to pay the higher initial sales charge level for the amount actually purchased.

•

Right Of Accumulation (ROA). Under the ROA, you may pay a reduced or no initial sales charge on purchases of Class A1 shares by aggregating the total dollar amount of your investment with your existing investments or any linked accounts in any class of any MFS fund, based on the current maximum public offering price of the funds. For example, you will pay a sales charge on your current purchase at the rate applicable to the total value of all eligible accounts based on the sales charge schedule above.

•

Eligible accounts that you may link under a LOI and ROA may include:

•

Individual accounts;

•

Joint accounts;

•

Trust accounts of which you, your spouse (or legal equivalent under applicable state law), or child under the age of 21 is the grantor;

•

MFS 529 College Savings Plan accounts;

•

Certain single-participant retirement plan accounts;

•

Certain Individual Retirement Accounts;

•

Uniform Gifts/Transfers to Minor Acts accounts; and

•

Accounts held in the name of your financial intermediary on your behalf, except accounts investing in Class W shares of certain MFS funds.

•

Shares held directly in a MFS fund account on which the broker/dealer is different than the broker/dealer for your current purchase.

you have not designated a broker/dealer) with certain supporting information at the time of each purchase regarding accounts held with the MFS funds that are eligible to be combined for purposes of a LOI or ROA. Such information may include shareholder identification numbers or applicable account numbers or account statements. You should request that your financial intermediary provide this information to the funds or their agents when placing each purchase order.

Special Note for LOI or ROA eligible accounts linked prior to May 1, 2006. Any LOI or ROA eligible accounts linked prior to May 1, 2006, will remain linked to the extent the broker/dealer information for such accounts is not modified. In the event you change the broker/dealer for any such account, your accounts will no longer be eligible to be linked under a LOI or ROA. In addition, you will not be able to link additional accounts to the extent they do not meet the criteria discussed above.

•

Automatic Exchange Plan. If you have an account balance of at least $2,000 in the fund, you may participate in the automatic exchange plan, a dollar-cost averaging program. This plan permits you to make automatic periodic exchanges from Class A1 or Class B1 shares in your account in the fund for Class A or Class B shares, respectively, of other MFS funds. Exchanges will generally be made at net asset value without any sales charges. If you exchange shares out of the MFS Money Market Fund or MFS Government Money Market Fund, or if you exchange Class A shares out of the MFS Cash Reserve Fund into Class A shares of any other MFS fund, you will pay an initial sales charge if you have not already paid this charge on these shares.

under the plan(s) or January 1, 2007, whichever is later, and reset annually thereafter). For Class A1 shares, you may incur a CDSC when Class A1 shares are redeemed under this plan.

•

Distribution Reinvestment. You may automatically reinvest dividend and capital gain distributions in the same fund without paying an initial sales charge.

Distribution Investment Program. You may automatically reinvest dividend and capital gain distributions from your Class A1 or Class B1 shares into Class A or Class B shares, respectively, of another MFS fund without paying a CDSC or an initial sales charge.

Calculation Of CDSC. As discussed above, certain investments in Class A1 and Class B1 shares are subject to a CDSC. For purposes of calculating the CDSC, purchases made on any day during a calendar month will age one month on the last day of that month, and on the last day of each subsequent month. For example, a 1% CDSC on Class A1 shares purchased on August 10 will expire at the close of business on July 31 of the following calendar year, and a redemption of those shares made on or after August 1 of the following calendar year will not be subject to the CDSC.

Distribution and Service Fees

The fund has adopted a plan in accordance with Rule 12b-1 under the Investment Company Act of 1940, as amended (the “Distribution Plan”). Under the Distribution Plan, the fund pays distribution and service fees to MFD to support the sale and distribution of Class B1 shares, as well as shareholder servicing and account maintenance activities. These distribution and service fees equal on an annual basis up to the following maximum percentages of average daily net assets of the class:


Class	Maximum Distribution Fee		Maximum Service Fee		Maximum Total Distribution and Service Fee
Class B1	0.75	%	0.25	%	1.00	%

These fees are paid out of fund assets of the applicable class of shares. Because these fees are an ongoing expense of the fund, they increase the cost of your investment over time and may cost you more than other types of sales charges. The 0.25% per annum Class B1 service fee is paid by the fund only during the first year after you purchase Class B1 shares; thereafter, payment of Class B1 service fee is currently not being imposed and may be imposed only with the approval of the Board of Trustees which oversees the fund.

The fund has not adopted a Rule 12b-1 plan with respect to its Class A1 shares.

Financial Intermediary Compensation

Financial intermediaries may receive up front commissions of up to the following percentage amounts for sales of the following share classes:


Share Class	Up Front Commission as a Percentage of Offering Price
Class A1	4.75	%
Class B1	3.75	%

intermediary for information about any payments it receives from MFD and any services it provides, as well as about fees and/or commissions it charges. Financial intermediaries that sell fund shares may also act as a broker/dealer in connection with a MFS fund’s purchase or sale of portfolio securities. However, the fund and MFS do not consider financial intermediaries’ sales of shares of a MFS fund as a factor when choosing broker/dealers to effect portfolio transactions for the MFS funds.

HOW TO PURCHASE, REDEEM, AND EXCHANGE SHARES

How to Purchase Shares

Class A1 and Class B1 shares are available only to shareholder accounts opened in the fund in connection with the fund’s acquisition of all the assets and certain stated liabilities of MFS Municipal Bond Fund pursuant to an agreement and plan of reorganization. Class A1 and Class B1 shareholders of the fund can purchase additional Class A1 and Class B1 shares through accounts opened in connection with the reorganization.

However, once a Class A1 or Class B1 shareholder has closed their account in the fund, they will be prohibited from purchasing Class A1 or B1 shares in the future.

Purchases of Class B and Class B1 shares are subject to a total account value limitation at the time of purchase of $99,999. If your existing accounts for all share classes held with the MFS funds have a total value equal to $99,999 for Class B or Class B1 share purchases, you will not be able to purchase Class B1 shares. For the purpose of determining your total account value, existing accounts for all share classes held with the MFS funds that are linked under a LOI or ROA will be included.

The fund or its agents may at their discretion accept a purchase request for Class B1 shares that would otherwise exceed the total account value limitation of $99,999 under certain circumstances, including, but not limited to, purchases by certain types of group retirement plans sponsored or serviced by MFS or an affiliate.

•

Additional Purchases Directly Through MFSC.

•

By Mail. You may purchase additional shares by mailing a check with the returnable portion of your statement to MFSC.

•

By Wire. To purchase additional shares by wire, call MFSC for instructions.

•

How to Redeem Shares

The fund normally sends out your redemption proceeds within seven days after your request is received in proper form. Under unusual

circumstances, such as when the New York Stock Exchange is closed, trading on the Exchange is restricted, or as permitted by the SEC, the fund may suspend redemptions or postpone payment for more than seven days.

You may redeem your shares either by having your financial intermediary process your redemption or by contacting MFSC directly.

Redeeming Directly Through MFSC.

•

By Mail. To redeem shares by mail, you can send a letter to MFSC with the name of the fund, your account number, and the number of shares or dollar amount to be redeemed.

•

Systematic Withdrawal Plan. For Class A1 and Class B1 shares shares, you may elect to automatically receive (or designate someone else to receive) regular periodic payments through an automatic redemption of such classes. Please contact MFSC for details.

•

Checkwriting. You may redeem your Class A1 shares by writing checks against your account. There is no charge for this service. You must elect this privilege on your account application to use this service. Shares in your account equal in value to the amount of the check plus the applicable CDSC (if any) and any income tax required to be withheld (if any), are redeemed to cover the amount of the check. If your account value is not great enough to cover these amounts, your check will be dishonored. Checkwriting may not be available for all accounts.

Redeeming Through Your Financial Intermediary. You can have your financial intermediary process a redemption on your behalf. Your financial intermediary will be responsible for furnishing all necessary documents to MFSC and may charge you for this service.

How to Exchange Shares

An exchange involves the redemption of shares of one fund and the purchase of shares of another fund.

Exchange Privilege. You can exchange your Class A1 or Class B1 shares for Class A and Class B shares, respectively, of most other MFS funds by having your financial intermediary process your exchange request or by contacting MFSC directly.

You can exchange your Class A1 shares for shares of the MFS Money Market Fund or the MFS Government Money Market Fund.

Exchanges of shares of the MFS Money Market Fund or the MFS Government Money Market Fund or of Class A or Class B shares of other MFS funds for shares of Class A1 or Class B1 of the fund, respectively, are not permitted.

Other Considerations

Frequent Trading

•

purchase side of the exchange will be processed. Each MFS fund reserves the right to delay for one business day the processing of exchange requests in the event that, in MFSC's judgment, such delay would be in the fund’s best interest, in which case both the redemption and purchase side of the exchange will receive the fund’s net asset values at the conclusion of the delay period.

•

In addition, MFSC may make exceptions to this policy if, in its judgment, the transaction does not represent frequent trading activity, such as purchases made through systematic purchase plans or payroll contributions. In applying this policy, MFSC considers the information available to it at the time and reserves the right to consider trading multiple accounts under common ownership, control, or influence to be trading out of a single account.

•

the MFS funds’ policies, may permit certain transactions not permitted by the MFS funds’ policies, or prohibit transactions not subject to the MFS funds’ policies. You should consult your financial intermediary regarding the application of these limitations and whether your financial intermediary imposes any additional or different limitations.

•

frequent trading policies and does not have its own policy to restrict frequent trading that MFSC determines is reasonably designed to identify and curtail trading activity that is not in the best interests if the funds (a “Non Adopted Policy”), MFSC may rely upon the financial intermediary to enforce its Non Adopted Policy (if any). MFSC expects to request underlying shareholder data from financial intermediaries with Non Adopted Policies more frequently than from financial intermediaries with Adopted Financial Intermediary Policies.

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unable to provide MFSC with information about underlying shareholder level activity. There is no assurance that MFSC will request data with sufficient frequency to detect or deter frequent trading in omnibus accounts effectively. Shareholders seeking to engage in frequent trading practices may deploy a variety of strategies to avoid detection, and, despite the efforts of MFSC to prevent frequent trading, there is no assurance that MFSC will be able to identify such shareholders or curtail their trading practices.

•

OTHER INFORMATION

Valuation

Distributions

The fund intends to declare a dividend daily and to pay these dividends to shareholders at least monthly.

Any capital gains are distributed at least annually.

Distribution Options

The following distribution options are generally available:

•

Dividend and capital gain distributions reinvested in additional shares (this option will be assigned if no other option is specified);

•

Dividend distributions in cash; capital gain distributions reinvested in additional shares;

•

Dividend and capital gain distributions in cash; or

•

Dividend and capital gain distributions reinvested into the same class of shares of another MFS Fund.

The distribution option for accounts with dividend distributions of less than $10 will generally be changed to reinvestment in additional shares of the fund. If you have elected to receive distributions in cash, and the postal service is unable to deliver checks to your address of record, or you do not respond to mailings from MFSC with regard to uncashed distribution checks, your distribution option may be converted to having all distributions reinvested in additional shares. You should contact MFSC to change your distribution option, and your request to do so must be received by MFSC before the record date for a distribution in order to be effective for that distribution. No interest will accrue on amounts represented by uncashed distribution checks.

Tax Considerations

Any gain resulting from the sale or exchange of your shares will generally also be subject to tax.

Long-term capital gain rates applicable to most individuals have been temporarily reduced for taxable years beginning before January 1, 2011.

The Form 1099 that is mailed to you every January details your distributions and how they are treated for federal tax purposes.

Provision of Annual and Semiannual Reports and Prospectuses

FINANCIAL HIGHLIGHTS

Year Ended 3/31


	2008(i)
Class A1
Net asset value, beginning of period	$	8.39

Income (loss) from investment operations
Net investment income (d)	$	0.34
Net realized and unrealized gain (loss) on investments		(0.18	)(g)

Total from investment operations	$	0.16

Less distributions declared to shareholders
From net investment income	$	(0.33	)
From net realized gain on investments		(0.01	)

Total distributions declared to shareholders	$	(0.34	)

Net asset value, end of period	$	8.21

Total return (%) (r)(s)(t)		1.84	(n)

Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		0.79	(a)
Expenses after expense reductions (f)		0.54	(a)
Expenses after expense reductions and excluding interest expense and fees (f)(l)		0.44	(a)
Net investment income		5.26	(a)
Portfolio turnover		32
Net assets at end of period (000 omitted)	$	864,341


	Year Ended 3/31 2008(i)
Class B1
Net asset value, beginning of period	$	8.40

Income (loss) from investment operations
Net investment income (d)	$	0.29
Net realized and unrealized gain (loss) on investments		(0.18	)(g)

Total from investment operations	$	0.11

Less distributions declared to shareholders
From net investment income	$	(0.28	)
From net realized gain on investments		(0.01	)

Total distributions declared to shareholders	$	(0.29	)

Net asset value, end of period	$	8.22

Total return (%) (r)(s)(t)		1.24	(n)

Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		1.55	(a)
Expenses after expense reductions (f)		1.30	(a)
Expenses after expense reductions and excluding interest expense and fees(f) (l)		1.21	(a)
Net investment income		4.50	(a)
Portfolio turnover		32
Net assets at end of period (000 omitted)	$	26,618

(a)	Annualized

(d)	Per share data are based on average shares outstanding.

(f)	Ratios do not reflect reductions from fees paid indirectly, if applicable.

(g)	The per share amount is not in accordance with the net realized and unrealized gain/loss for the period because of the timing of sales of fund shares and the per share amount of realized and unrealized gains and losses at such time.

(i)	For the period from the class' inception, June 25, 2007 (Classes A1 and B1) through the stated period end.

(l)	Interest expense and fees relate to payments made to the holder of the floating rate certificate from trust assets.

(n)	Not annualized

(r)	Certain expenses have been reduced without which performance would have been lower.

(s)	From time to time the fund may receive proceeds from litigation settlements, without which performance would be lower.

(t)	Total returns do not include any applicable sales charges.

MFS Municipal Income Fund

If you want more information about MFS Municipal Income Fund, the following documents are available free upon request:

Statement of Additional Information (SAI). The SAI, dated August 1, 2008, provides more detailed information about the fund 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 fund, and make inquiries about the fund, by contacting:

MFS Service Center, Inc.

500 Boylston Street

Boston, MA 02116-3741

Telephone: 1-800-225-2606

Internet: mfs.com

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

Public Reference Room

Securities and Exchange Commission

100 F Street, NE

Washington, D.C., 20549-0102

The fund’s Investment Company Act file number is 811-4096.

Statement of Additional

Information

August 1, 2008

MFS^® Municipal Income Fund

A series of MFS Municipal Series Trust

500 Boylston Street, Boston, MA 02116

This Statement of Additional Information (“SAI”) contains additional information about the Fund and should be read in conjunction with the Fund’s Prospectus dated August 1, 2008. The Fund’s financial statements are incorporated into this SAI by reference to the Fund’s most recent Annual Report to shareholders. A copy of the Annual Report accompanies this SAI. You may obtain a copy of the Fund’s Prospectus and Annual Report without charge by contacting the Fund’s transfer agent, MFS Service Center, Inc. (please see the back cover of Part II of this SAI for address and telephone number).

This SAI is divided into two Parts — Part I and Part II. Part I contains information that is particular to the Fund, while Part II contains information that generally applies to all of the funds in the MFS Family of Funds (the “MFS Funds”). Each part of this SAI has a variety of appendices which can be found at the end of Part I and Part II, respectively.

This SAI is NOT a prospectus and is authorized for distribution to prospective investors only if preceded or accompanied by a current prospectus.

LMB-SAI-8/08

Statement of Additional Information (SAI) – PART I

Part I of this SAI contains information that is particular to the Fund.


DEFINITIONS		1

MANAGEMENT OF THE FUND		1

SALES CHARGES AND DISTRIBUTION PLAN PAYMENTS		3

INVESTMENT STRATEGIES, RISKS, AND RESTRICTIONS		3

TAX CONSIDERATIONS		3

PORTFOLIO TRANSACTIONS AND BROKERAGE COMMISSIONS		4

INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM AND FINANCIAL STATEMENTS		4

APPENDIX A – TRUSTEE COMPENSATION AND COMMITTEES		A-1

APPENDIX B – SHARE OWNERSHIP		B-1

APPENDIX C – PORTFOLIO MANAGER(S)		C-1

APPENDIX D – CERTAIN SERVICE PROVIDER COMPENSATION		D-1

APPENDIX E – SALES CHARGES AND DISTRIBUTION PLAN PAYMENTS		E-1

APPENDIX F – PORTFOLIO TRANSACTIONS AND BROKERAGE COMMISSIONS		F-1

DEFINITIONS

“Fund” – MFS Municipal Income Fund, a series of the Trust. The Fund is the successor to MFS Lifetime Municipal Bond Fund, which was reorganized as a series of the Trust on September 7, 1993.

“Trust” – MFS Municipal Series Trust, a Massachusetts business trust organized on August 23, 1984. The Trust was previously known as MFS Multi-State Municipal Bond Trust (prior to August 20, 1993), MFS Managed Multi-State Municipal Bond Trust (prior to August 3, 1992), and MFS Managed Multi-State Tax-Exempt Trust (prior to August 3, 1988).

“MFS” or “Adviser” – Massachusetts Financial Services Company, a Delaware corporation.

“MFD” – MFS Fund Distributors, Inc., a Delaware corporation.

“MFSC” – MFS Service Center, Inc., a Delaware corporation.

“Prospectus” – The Prospectus of the Fund, dated August 1, 2008, as amended or supplemented from time to time.

“1940 Act” – The Investment Company Act of 1940, as amended.

“SEC” – Securities and Exchange Commission.

MANAGEMENT OF THE FUND

The Fund

The Fund is a diversified series of the Trust. The Trust is an open-end management investment company.

Trustees and Officers – Identification and Background

The identification and background of the Trustees and officers of the Trust are set forth in Appendix A to Part II of this SAI.

Trustee Compensation and Committees

Compensation paid to the non-interested Trustees for certain specified periods, as well as information regarding committees of the Board of Trustees, is set forth in Appendix A to this Part I.

Part - 1 - 1

Share Ownership

Information concerning the ownership of Fund shares by Trustees and officers of the Trust as a group, as well as the dollar value range of each Trustee’s share ownership in the Fund and, on an aggregate basis, in all MFS Funds overseen by the Trustee, by investors who are deemed to “control” the Fund, if any, and by investors who own 5% or more of any class of Fund shares, if any, is set forth in Appendix B to this Part I.

Portfolio Manager

Information regarding the Fund’s portfolio manager, including other accounts managed, compensation, ownership of Fund shares, and possible conflicts of interest, is set forth in Appendix C to this Part I.

Certain Service Provider Compensation

Compensation paid by the Fund to certain of its service providers for advisory services, administrative services, and transfer agency services, for certain specified periods, is set forth in Appendix D to this Part I.

Custodian

JPMorgan Chase Bank, with a place of business at One Chase Manhattan Plaza, New York, NY 10081, serves as a custodian of the assets of the Fund (the “Custodian”). The Custodian is responsible for safekeeping and controlling the Fund’s cash and securities, handling the receipt and delivery of securities, collecting interest and dividends on the Fund’s investments, serving as the Fund’s foreign custody manager, and providing reports on foreign securities depositaries. An affiliate of the Custodian, J. P. Morgan Investor Services Co., with a place of business at 73 Tremont Street, Boston, MA 02108, is responsible for maintaining books of original entry and other required books and accounts for the Fund and calculating the daily net asset value of each class of shares of the Fund. The Fund may invest in securities of the Custodian and its affiliates and may deal with the Custodian and its affiliates as principal in securities transactions.

The Fund has an expense offset arrangement that reduces the Fund’s custodian fees based upon the amount of cash maintained by the Fund with its custodian.

Part - 1 - 2

SALES CHARGES AND DISTRIBUTION PLAN PAYMENTS

Sales Charges

Sales charges paid for certain specified periods in connection with the purchase and sale of the Fund’s shares are set forth in Appendix E to this Part I.

Distribution Plan Payments

Payments made by the Fund under the Fund’s plan in accordance with Rule 12b-1 under the Investment Company Act of 1940, as amended (the “Distribution Plan”), for the Fund’s most recent fiscal year, are set forth in Appendix E to this Part I.

INVESTMENT STRATEGIES, RISKS, AND RESTRICTIONS

Investment Strategies and Risks

Certain investment strategies and risks are described in Appendix E to Part II of this SAI.

Investment Restrictions

The Fund has adopted certain investment restrictions which are described in Appendix F of Part II of this SAI.

TAX CONSIDERATIONS

For a discussion of tax considerations, see Part II of this SAI.

Part - 1 - 3

PORTFOLIO TRANSACTIONS AND BROKERAGE COMMISSIONS

Brokerage commissions paid by the Fund for certain specified periods, information concerning purchases by the Fund of securities issued by its regular broker/dealers for its most recent fiscal year, and information concerning the amount of transactions and related commissions to broker/dealer firms that MFS has determined provide valuable research for the Fund’s most recent fiscal year, are set forth in Appendix F to this Part I. Portfolio transactions and brokerage commissions are more fully described in Part II of this SAI under the heading “Portfolio Transactions and Brokerage Commissions.”

INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM AND FINANCIAL STATEMENTS

Deloitte & Touche LLP is the independent registered public accounting firm, providing audit services, tax return review, and other related services and assistance in connection with the review of various Securities and Exchange Commission filings.

The Fund’s Financial Statements and Financial Highlights for the fiscal year ended March 31, 2008, are incorporated by reference into this SAI from the Fund’s Annual Report to shareholders and have been audited by Deloitte & Touche LLP, independent registered public accounting firm, as stated in their report, which is incorporated herein by reference, and have been so incorporated in reliance upon reports of such firm, given upon their authority as experts in accounting and auditing. A copy of the Fund’s Annual Report accompanies this SAI.

Part - 1 - 4

PART I – APPENDIX A

TRUSTEE COMPENSATION AND COMMITTEES

The Fund pays the non-interested Trustees an annual fee plus a fee for each meeting attended. In addition, the non-interested Trustees are reimbursed for their out-of-pocket expenses.

Trustee Compensation Table


Name and Position	Fees from Fund⁽¹⁾		Retirement Benefits Accrued as Part of Fund Expense		Total Fees from Fund and Fund Complex⁽²⁾
Interested Trustees
Robert J. Manning		N/A		N/A		N/A
Robert C. Pozen		N/A		N/A		N/A
Non-Interested Trustees
Robert E. Butler	$	1,766		N/A	$	229,619
Lawrence H. Cohn, M.D	$	1,723	$	0	$	228,509
David H. Gunning	$	1,885		N/A	$	248,508
William R. Gutow	$	1,732		N/A	$	228,509
Michael Hegarty	$	1,728		N/A	$	226,509
J. Atwood Ives	$	2,337	$	0	$	302,509
Lawrence T. Perera	$	1,703	$	0	$	226,953
J. Dale Sherratt	$	2,035	$	0	$	268,507
Laurie J. Thomsen	$	1,889		N/A	$	248,508
Robert W. Uek	$	1,926		N/A	$	254,142

(1)	For the fiscal year ended March 31, 2008.

(2)	Information provided is for calendar year 2007. Each Trustee receiving compensation served as Trustee of 98 funds within the MFS Fund Complex (having aggregate net assets at December 31, 2007, of approximately $106 billion).

Retirement Benefit Deferral Plan— Under a Retirement Benefit Deferral Plan, certain Trustees have deferred benefits from a prior retirement plan. The value of the benefits is periodically readjusted as though the Trustee had invested an equivalent amount in Class A shares of the Fund(s) designated by such Trustee. The value of the deferred benefits will be paid to the Trustees upon retirement or thereafter. The plan does not obligate a Fund to retain the services of any Trustee or pay any particular level of compensation to any Trustee. The plan is not funded and a Fund’s obligation to pay the Trustee’s deferred compensation is a general unsecured obligation.

Part - 1 - A - 1

Committees

The Board has established the following Committees:

Name of

Committee

Number of
Meetings in
Last Fiscal
Year

Functions

Current Members¹

AUDIT COMMITTEE

Oversees the accounting and auditing procedures of the Fund and, among other duties, considers the selection of the independent accountants for the Fund and the scope of the audit, and considers the effect on the independence of those accountants of any non-audit services such accountants provide to the Fund and any audit or non-audit services such accountants provide to other MFS Funds, MFS and/or certain affiliates. The Committee is also responsible for establishing procedures for the receipt, retention, and treatment of complaints received by the Fund regarding accounting, internal accounting controls, or auditing matters and the confidential, anonymous submission of concerns regarding questionable fund accounting matters by officers of the Fund and employees of the Fund’s investment adviser, administrator, principal underwriter, or any other provider of accounting-related services to the Fund.

Butler*, Gutow*, Sherratt*, Thomsen*, and Uek*

Part - 1 - A - 2

Part - 1 - A - 3

Part - 1 - A - 4

Part - 1 - A - 5

Part - 1 - A - 6

1)	The Trustees’ identification and background are set forth in Appendix A to Part II of this SAI.

*	Non-interested or independent Trustees. Although Mr. Ives is not a member of all Committees of the Board, he is invited to and attends many of the Committees’ meetings in his capacity as Chair of the Trustees.

Part - 1 - A - 7

PART I – APPENDIX B

SHARE OWNERSHIP

Ownership By Trustees and Officers

As of June 30, 2008, the current Trustees and officers of the Trust as a group owned less than 1% of any class of the Fund’s shares. The Board of Trustees has adopted a policy requiring that each Non-Interested Trustee invest on an aggregate basis, within two years of membership on the Board of Trustees, an amount equal to his or her prior calendar year’s Trustee fees in shares of the MFS funds overseen by such Trustee. The following table shows the dollar range of equity securities beneficially owned by each current Trustee in the Fund and, on an aggregate basis, in all MFS Funds overseen by each current Trustee, as of December 31, 2007.

The following dollar ranges apply:

N. None

A. $1 – $10,000

B. $10,001 – $50,000

C. $50,001 – $100,000

D. $100,001 – $225,000

E. Over $225,000

Part -1 - B - 1


Name of Trustee	Dollar Range of Equity Securities in the Fund	Aggregate Dollar Range of Equity Securities in All MFS Funds Overseen by Trustee
Interested Trustees
Robert J. Manning	N	E
Robert C. Pozen	N	E
Non-Interested Trustees
Robert E. Butler	N	E
Lawrence H. Cohn, M.D	N	E
David H. Gunning	N	E
William R. Gutow	N	E
Michael Hegarty	N	E
J. Atwood Ives	B	E
Lawrence T. Perera	A	E
J. Dale Sherratt	N	E
Laurie J. Thomsen	N	E
Robert W. Uek	N	E

25% or Greater Ownership of the Fund

The following table identifies those investors who own 25% or more of the Fund’s shares (all share classes taken together) as of June 30, 2008. All holdings are of record unless otherwise indicated.


Name and Address of Investor		Percentage Ownership
N/A		N/A

5% or Greater Ownership of Share Class

The following table identifies those investors who own 5% or more of any class of the Fund’s shares as of June 30, 2008. All holdings are of record unless otherwise indicated.

Name and Address of Investor

Percentage Ownership

Citigroup Global Markets Inc

Surpas House Account

ATTN: Cindy Tempesta 7^th Floor

333 W 34^th Street

New York NY 10001- 2402

5.96% of Class A1 Shares

10.65% of Class B1

5.69% of Class C Shares

Part - 1 - B - 2


Name and Address of Investor		Percentage Ownership
Merrill Lynch Pierce Fenner & Smith, Inc. For the Sole Benefit of its Customers 4800 Deerlake Drive East Jacksonville, FL 32246-6484		7.2% of Class A Shares 13.16% of Class B Shares 11.91% of Class B1 Shares 17.86% of Class C Shares

Charles Schwab & Co. Inc. FBO Clearing Customers 101 Montgomery St San Francisco CA 94104-4151		6.77% of Class A Shares

Part - 1 - B - 3

PART I – APPENDIX C

PORTFOLIO MANAGER(S)

Compensation

Portfolio manager total cash compensation is a combination of base salary and performance bonus:

Base Salary – Base salary represents a smaller percentage of portfolio manager total cash compensation (generally below 10%) than performance bonus.

Performance Bonus – Generally, the performance bonus represents a majority of portfolio manager total cash compensation.

The performance bonus is based on a combination of quantitative and qualitative factors, with more weight given to the former (generally over 60%) and less weight given to the latter.

The quantitative portion is based on the pre-tax performance of assets managed by the portfolio manager over a one-, three-, and five-year period relative to peer group universes and/or indices. As of December 31, 2007, the following benchmarks were used:

Benchmark

Lipper General Municipal Debt Funds

Lipper Short-Intermediate Municipal Debt Funds

Lipper High Yield Municipal Debt Funds

Lipper General US Government Funds

Lehman Brothers Municipal Index

Lehman Brothers Government Mortgage Index

Morningstar Dollar Government Bond Funds

Additional or different benchmarks, including versions of indices and custom indices may also be used. Primary weight is given to portfolio performance over a three-year time period with lesser consideration given to portfolio performance over one-year and five-year periods (adjusted as appropriate if the portfolio manager has served for less than five years).

Part - 1 - C - 1

The qualitative portion is based on the results of an annual internal peer review process (conducted by other portfolio managers, analysts, and traders) and management’s assessment of overall portfolio manager contributions to investor relations and the investment process (distinct from fund and other account performance).

Portfolio managers also typically benefit from the opportunity to participate in the MFS Equity Plan. Equity interests and/or options to acquire equity interests in MFS or its parent company are awarded by management, on a discretionary basis, taking into account tenure at MFS, contribution to the investment process, and other factors.

Finally, portfolio managers are provided with a benefits package including a defined contribution plan, health coverage and other insurance, which are available to other employees of MFS on substantially similar terms. The percentage such benefits represent of any portfolio manager’s compensation depends upon the length of the individual’s tenure at MFS and salary level, as well as other factors.

Ownership of Fund Shares

The following table shows the dollar range of equity securities of the Fund beneficially owned by the Fund’s portfolio manager(s) as of the Fund’s fiscal year ended March 31, 2008. The following dollar ranges apply:

N. None

A. $1 – $10,000

B. $10,001 – $50,000

C. $50,001 – $100,000

D. $100,001 – $500,000

E. $500,001 – $1,000,000

F. Over $1,000,000


Name of Portfolio Manager		Dollar Range of Equity Securities in Fund
Geoffrey L. Schechter		C

Part -1 - C - 2

Other Accounts

In addition to the Fund, the Fund’s portfolio manager is responsible (either individually or jointly) for the day-to-day management of certain other accounts, the number and assets of which, as of the Fund’s fiscal year ended March 31, 2008, were as follows:

Registered
Investment
Companies*

Other Pooled
Investment Vehicles

Other Accounts

Name

Number of
Accounts

Total
Assets

Number of
Accounts

Total Assets

Number of
Accounts

Total
Assets

Geoffrey L. Schechter

6.6 billion

398 million

*	Includes the Fund

Advisory fees are not based upon performance of any of the accounts identified in the table above.

Potential Conflicts of Interest

The Adviser seeks to identify potential conflicts of interest resulting from a portfolio manager’s management of both the Fund and other accounts, and has adopted policies and procedures designed to address such potential conflicts.

The management of multiple funds and accounts (including proprietary accounts) may give rise to potential conflicts of interest if the funds and accounts have different objectives and strategies, benchmarks, time horizons and fees as a portfolio manager must allocate his or her time and investment ideas across multiple funds and accounts. In certain instances there may be securities which are suitable for the Fund’s portfolio as well as for accounts of the Adviser or its subsidiaries with similar investment objectives. A Fund’s trade allocation policies may give rise to conflicts of interest if the Fund’s orders do not get fully executed or are delayed in getting executed due to being aggregated with those of other accounts of the Adviser or its subsidiaries. A portfolio manager may execute transactions for another fund or account that may adversely impact the value of the Fund’s investments. Investments selected for funds or accounts other than the Fund may outperform investments selected for the Fund.

Part - 1 - C - 3

recognized that in some cases this system could have a detrimental effect on the price or volume of the security as far as the Fund is concerned. In most cases, however, the Adviser believes that the Fund’s ability to participate in volume transactions will produce better executions for the Fund.

The Adviser does not receive a performance fee for its management of the Fund. As a result, the Adviser and/or a portfolio manager may have a financial incentive to allocate favorable or limited opportunity investments or structure the timing of investments to favor accounts other than the Fund - for instance, those that pay a higher advisory fee and/or have a performance fee.

Part - 1 - C - 4

PART I – APPENDIX D

CERTAIN SERVICE PROVIDER COMPENSATION

Compensation paid by the Fund for advisory services, administrative services, and transfer agency services, over the specified periods is set forth below. For information regarding sales charges and distribution payments paid to MFD, see Appendix E to this Part I.


Fiscal Year Ended	Amount Paid to MFS for Advisory Services After Waivers		Amount Waived by MFS for Advisory Services		Amount Paid to MFSC for Transfer Agency Services⁽¹⁾		Amount Paid to MFS for General Administrative Services
March 31, 2008	$	3,113,241	$	2,594,360	$	664,413	$	160,858
March 31, 2007	$	923,010	$	769,215		N/A	$	63,766
March 31, 2006	$	953,768	$	794,807		N/A	$	43,463

(1)	Amount paid to MFSC for transfer agency services includes reimbursements for certain out-of-pocket expenses and payments made under agreements with affiliated and unaffiliated entities that provide subaccounting services.

Part - 1 - D - 1

PART I – APPENDIX E

SALES CHARGES AND DISTRIBUTION PLAN PAYMENTS

Sales Charges

The following sales charges were paid during the specified periods:


	Class A Initial Sales Charges:						CDSC Paid to MFD On:
Fiscal Year End	Total		Retained by MFD		Reallowed to Financial Intermediaries		Class A Shares		Class B Shares		Class C Shares
March 31, 2008	$	708,154	$	99,518	$	457,118	$	6,770	$	31,865	$	4,854


*Class A1 Initial Sales Charges:**				CDSC Paid to MFD On:
Retained by MFD		Reallowed to Financial Intermediaries		Class A1 Shares		Class B1 Shares
$	26,752	$	124,766	$	123	$	29,961


	Class A Initial Sales Charges:						CDSC Paid to MFD On:
Fiscal Year End	Total		Retained by MFD		Reallowed to Financial Intermediaries		Class A Shares		Class B Shares		Class C Shares
March 31, 2007	$	292,778	$	38,270	$	254,508	$	45,914	$	58,195	$	3,885
March 31, 2006	$	336,043	$	57,357	$	278,686	$	8,903	$	59,246	$	4,632

*	From the period starting with the Class A1 shares inception on June 22, 2007.

Part - 1 - E - 1

Distribution Plan Payments

During the fiscal year ended March 31, 2008, the Fund made the following Distribution Plan payments:


	Amount of Distribution and/or Service Fees:
Class of Shares	Paid by Fund		Retained by MFD		Paid to Financial Intermediaries⁽¹⁾
Class A Shares	$	644,964	$	39,488	$	605,476
Class B Shares	$	415,728	$	359,514	$	56,214
Class C Shares	$	364,047	$	56,940	$	307,107

(1)	May include amounts paid to financial intermediaries affiliated with MFD.

Amounts retained by MFD may represent fees paid to MFD but not yet paid to intermediaries as of the close of the period, compensation to MFD for commissions advanced by MFD to financial intermediaries upon sale of Fund shares, and/or compensation for MFD’s distribution and servicing costs.

Part - 1 - E - 2

PART I – APPENDIX F

PORTFOLIO TRANSACTIONS AND BROKERAGE COMMISSIONS

Brokerage Commissions

The following brokerage commissions were paid by the Fund during the specified time periods:


Fiscal Year End		Brokerage Commissions Paid By Fund
March 31, 2008		N/A
March 31, 2007		N/A
March 31, 2006		N/A

Securities Issued By Regular Broker/Dealers

During the fiscal year ended March 31, 2008, the Fund purchased securities issued by the following regular broker/dealers of the Fund, which had the following value as of March 31, 2008:


Broker/Dealer		Value of Securities
None		N/A

Transactions with Research Firms

During the fiscal year ended March 31, 2008, the Fund allocated the following amount of transactions, and related commissions, to broker/dealer firms that have been deemed by MFS to provide valuable Research (“Research Firms”). The provision of Research was not necessarily a factor in the placement of this business with such Research Firms. ⁽¹⁾

Dollar Amount of Transactions with

Research Firms

Commissions Paid on Transactions
With Research Firms

(1)	The amounts shown do not include transactions directed to electronic communication networks (ECNs) owned by the Research Firms.

Part - 1 - F - 1

Class A Shares

Class B Shares

Class C Shares (California, New York, North Carolina and Virginia funds only)

MFS Municipal Series Trust Prospectus August 1, 2008

MFS Alabama Municipal Bond Fund

MFS Arkansas Municipal Bond Fund

MFS California Municipal Bond Fund

MFS Florida Municipal Bond Fund

MFS Georgia Municipal Bond Fund

MFS Maryland Municipal Bond Fund

MFS Massachusetts Municipal Bond Fund

MFS Mississippi Municipal Bond Fund

MFS New York Municipal Bond Fund

MFS North Carolina Municipal Bond Fund

MFS Pennsylvania Municipal Bond Fund

MFS South Carolina Municipal Bond Fund

MFS Tennessee Municipal Bond Fund

MFS Virginia Municipal Bond Fund

MFS West Virginia Municipal Bond Fund

This Prospectus describes each of the funds listed above. The investment objective of each fund is to seek total return with an emphasis on income exempt from federal income tax and personal income tax, if any, of the named state, but also considering capital appreciation.


RISK RETURN SUMMARY		1
EXPENSE SUMMARY		36
MANAGEMENT OF THE FUND		45
DESCRIPTION OF SHARE CLASSES		49
HOW TO PURCHASE, REDEEM, AND EXCHANGE SHARES		59
OTHER INFORMATION		70
FINANCIAL HIGHLIGHTS		77

RISK RETURN SUMMARY

Investment Objective

Each fund’s investment objective is to seek total return with an emphasis on income exempt from federal income tax and personal income tax, if any, of the named state, but also considering capital appreciation. Each fund’s objective may be changed without shareholder approval.

Principal Investment Strategies

Each fund invests, under normal market conditions, at least 80% of its net assets in securities and other investments, the interest on which is exempt from federal income tax and personal income tax, if any, of the named state. This policy may not be changed without shareholder approval. Interest from the fund’s investments may be subject to the federal alternative minimum tax.

MFS (Massachusetts Financial Services Company, each fund’s investment adviser) normally invests each fund’s assets primarily in municipal instruments.

MFS may invest 25% or more of each fund’s assets in municipal instruments that finance similar projects, such as those relating to education, healthcare, housing, utilities, water or sewers. Municipal instruments whose interest is exempt from federal and state personal income tax include instruments issued by U.S. territories and possessions (such as Puerto Rico) and their political subdivisions and public corporations. Although MFS seeks to invest each fund’s assets in municipal instruments whose interest is exempt from federal and state personal income tax, MFS may also invest in taxable instruments.

MFS primarily invests each fund’s assets in investment grade debt instruments, but may also invest in lower quality debt instruments.

MFS invests a high percentage of each fund’s assets in municipal issuers of the named state.

The MFS Arkansas, Maryland, Massachusetts, Mississippi, New York, North Carolina, and West Virginia Funds are each non-diversified funds. This means that MFS may invest a relatively high percentage of each fund’s assets in a single issuer or a small number of issuers.

MFS uses a bottom-up investment approach in buying and selling investments for each fund. Investments are selected primarily based on fundamental analysis of instruments and their issuers in light of current market, economic, political, and regulatory conditions. Factors considered may include the instrument’s credit quality, collateral characteristics, and indenture provisions, and the issuer’s management ability, capital structure, leverage, and ability to meet its current obligations. Quantitative analysis of the structure of the instrument and its features may also be considered.

MFS may engage in active and frequent trading in pursuing each fund's principal investment strategies.

In response to market, economic, political, or other conditions, MFS may depart from the fund’s principal investment strategies by temporarily investing for defensive purposes.

Principal Investment Types

issuer, by the current or anticipated revenues from a specific project or assets, by the issuer’s pledge to make annual appropriations for lease payments, or by domestic or foreign entities providing credit support, such as letters of credit, guarantees, or insurance.

Principal Risks

As with any mutual fund, you could lose money on your investment in a fund. An investment in a fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency.

The principal risks of investing in each fund are:

decline in response to changes in the financial condition of the issuer or borrower, changes in specific market, economic, industry, political, and regulatory conditions that affect a particular type of instrument, issuer, or borrower, and changes in general market, economic, political, and regulatory conditions. Certain unanticipated events, such as natural disasters, terrorist attacks, war, and other geopolitical events can have a dramatic adverse effect on the value of a debt instrument. For certain types of instruments, including derivatives, the value of the instrument depends in part on the credit quality of the counterparty to the transaction. For other types of debt instruments, including collateralized instruments, the price of the debt instrument also depends on the credit quality and adequacy of the underlying assets or collateral. Enforcing rights against the underlying assets or collateral may be difficult, or the underlying assets or collateral may be insufficient, if the issuer defaults.

principal are made prior to an instrument’s maturity. Instruments subject to prepayment can offer less potential for gains during a declining interest rate environment and greater potential for loss in a rising interest rate environment. In addition, prepayment rates are difficult to predict and the potential impact of prepayment on the price of a debt instrument depends on the terms of the instrument and can result in significant volatility.

Geographic Focus Risk: Each fund’s performance will be closely tied to the economic and political conditions in its namesake state, and can be more volatile than the performance of a more geographically diversified fund. These conditions may include constitutional or statutory limits on an issuer’s ability to raise revenues or increase taxes, anticipated or actual budget deficits or other financial difficulties, or changes in the credit quality of municipal issuers in the state. The principal factors affecting each state are as follows:

•

Alabama: Alabama’s economy relies in part on the textile, service, construction, manufacturing and forest products industries, all of which may be affected by cyclical changes. While average per capita income of Alabama residents has improved in recent years, certain areas of Alabama are among the poorest in the nation.

•

Arkansas: The Arkansas economy is reliant in part on the food processing and lumber and wood products industries. Downturns in these industries could adversely affect the state’s economy. The limits to growth in Arkansas are primarily related to labor supply shortages and infrastructure constrictions rather than external factors. Arkansas production and wealth prospects could be adversely affected if consumer confidence declines.

•

California: Due to a variety of factors, California and many of its local municipalities experienced credit rating downgrades during the 2001-2003 timeframe. In January 2003, the Governor indicated that

California has experienced the most dramatic decline in revenues since World War II and faced the most serious fiscal challenge in its history. However, California’s fiscal picture has improved over the last few fiscal years, and recent Governor’s Budgets have forecast an increase in California’s tax revenues. As of April 1, 2007, the S&P rating of California’s general obligation bonds was “A+,” Moody’s rating was “A1” and Fitch’s rating was “A+.”

Many municipal issuers depend upon real property taxes as a source of revenue. Voter-passed initiatives have limited real property taxes. This limit and other voter-passed initiatives also have made it difficult for California to balance its budget. For example, State and local governments are subject to limits on spending. In addition, California is required to guarantee a minimum level of spending on public education.

•

Florida: Florida does not impose an individual income tax on Florida residents. This could affect Florida’s ability to pay principal and interest in a timely manner, if an economic downswing occurs. Florida’s economy is heavily dependent on the tourism, agriculture and construction industries. South Florida is susceptible to economic difficulties from international trade and currency imbalances. North and Central Florida are impacted by damage to agriculture, especially the citrus and sugar industries.

•

Georgia: The national housing downturn, high energy prices and slowing consumer spending have had a negative impact on Georgia’s economy. Furthermore, drought conditions throughout Georgia and the Southeast could potentially impact manufacturing and agricultural activity in the state.

•

Maryland: From 2001 through 2006, inclusive, according to U.S. Department of Commerce statistics, average per capita personal income of Maryland residents ranked as the fourth (4^th) highest in the nation, and had been ranked fifth (5^th) in such category for at least each of the previous four (4) years. However, with respect to such personal income, Maryland is more reliant on the service and government sectors than the nation as a whole, while the manufacturing sector is much less significant in Maryland than nationwide. Therefore, a significant downturn in either the government or service sectors would have heightened impact on Maryland personal income, as a whole, possibly reducing certain municipalities’ revenues.

•

Massachusetts: The Commonwealth’s technology, financial services or health care industries could experience a downturn or fail to develop as expected, hurting the local economy.

•

Mississippi: Because Mississippi’s economy relies heavily on the manufacturing and service industries, its economy is sensitive to trends in those industries. Also, Mississippi’s financial strength in recent years is partially the result of substantial growth in the gaming and tourism industries and is therefore subject to changes in those industries and downturns in economy. While Mississippi’s financial condition has improved, it still ranks among the last of the states in per capita income.

•

New York: New York City and certain localities outside New York City have experienced financial problems; continuation of these problems could affect the overall fiscal health of New York State. In addition, financial market volatility poses a particularly large degree of uncertainty for New York due to the importance of the finance industry to the State’s economy. Furthermore, New York State, though its broad economic base generally supports such use, has relied on bond financing to a more extensive degree than almost any other State in the nation.

•

North Carolina: North Carolina has seen significant growth over the past twenty-five years, including increases in population, labor force, and per capita income. Nonetheless, it remains primarily a rural state. North Carolina’s economy consists of a combination of services, agriculture, trade, manufacturing and tourism.

•

Pennsylvania: Although Pennsylvania has been historically identified as a heavy-industry state, over 87% of total state employment is non-manufacturing employment. Thus, Pennsylvania’s economy may be disproportionately affected by economic downturns in non-manufacturing industries. Although Pennsylvania’s employment rate and bond ratings are generally on par with to slightly better than the national median, certain areas within the Commonwealth, particularly those areas that are more heavily reliant on a manufacturing economy, have worse employment rates and bond ratings.

•

South Carolina: South Carolina relies heavily on manufacturing, still largely related to the textile industry. Accordingly, the State’s manufacturing economy remains vulnerable to cycles. The State also has initiated an ambitious property tax relief program, though the funding level is determined annually.

•

Tennessee: Tennessee faces a recurring budget crisis for the current year that could lead to financial difficulty for the State. In response to a pattern of budget shortfalls, the Tennessee General Assembly passed the Tax Reform Act of 2002, increasing the sales tax to 7% on most non-food items and introducing a variety of tax increases on goods and businesses. Tennessee citizens also voted in 2002 to allow the Legislature to create a lottery to fund education initiatives. Tennessee is heavily reliant on the sales tax for revenue, the effectiveness of which, critics complain, is undermined by rising Internet sales. The State also relies largely on revenue from tourism and manufacturing, both of which are sensitive to the strength of the economy as a whole. Tennessee’s economic growth has slowed since approximately 1998 and has fallen behind the rate of economic growth for the nation. In 2008, Tennessee’s economy will be dependent upon the national economy as high energy prices and the continued housing crisis will weigh on consumer spending and result in slower growth in business investment. A recession does not seem likely in the short-term, but weaker economic conditions will prevail in 2008 compared to 2007.

•

Virginia: In Virginia, the major sources of personal income were the service industry, state and local government, the wholesale and retail trade industry, the finance, insurance and real estate industry, civilian federal government, the manufacturing industry, the construction industry and military federal government. As of 2006, per capita personal income was $39,564. As of July 2007, Virginia’s population was 7.7 million. From 1997 through 2007, the percentage of unemployment in Virginia has been less than the national unemployment rate. In 2007, the unemployment rate in Virginia was 3.1% compared to 4.6% nationally. Taxable retail sales in Virginia for 2006 totaled $89.5 billion.

•

West Virginia: West Virginia’s economic indicators are typically below national averages. Although the State’s economy continues to diversify, it is sensitive to trends in various industries such as mineral production, manufacturing, and tourism.

Non-Diversification Risk: Because MFS may invest a relatively large percentage of the assets of the MFS Arkansas, Maryland, Massachusetts, Mississippi, New York, North Carolina, and West Virginia Funds in a single issuer or small number of issuers, the performance of these funds could be closely tied to the value of that one issuer or issuers, and could be more volatile than the performance of more diversified funds.

Derivatives Risk: Derivatives can be highly volatile and involve risks in addition to the risks of the underlying indicator(s). Gains or losses from derivatives can be substantially greater than the derivatives’ original cost, and can sometimes be unlimited, and therefore, can involve leverage. Derivatives can be complex instruments and can involve analysis and processing that differs from that required for other investment types used by each fund. If the value of a derivative does not correlate well with the particular market or other asset class the derivative is intended to provide exposure to, the derivative may not have the effect anticipated. Derivatives can also reduce the opportunity for gains or result in losses by offsetting positive returns in other investments. Derivatives can be less liquid than other types of investments.

Leveraging Risk: Certain transactions, including when-issued, delayed-delivery, and forward commitment purchases, and the use of some derivatives, can result in leverage. Leverage involves investment exposure in an amount exceeding the initial investment. In transactions involving leverage, a relatively small change in an underlying indicator can lead to significantly larger losses to each fund. Leverage can cause increased volatility by magnifying gains or losses.

Investment Selection Risk: The MFS analysis of an investment can be incorrect and its selection of investments can lead to an investment focus that results in each fund underperforming other funds with similar investment strategies and/or underperforming the markets in which each fund invests.

Frequent Trading Risk: Frequent trading increases transaction costs, which may reduce each fund’s return. Frequent trading can also result in the realization of a higher percentage of short-term capital gains and a lower percentage of long-term capital gains as compared to a fund that trades less frequently. Because short-term capital gains are distributed as ordinary income, this would generally increase your tax liability unless you hold your shares through a tax-deferred or tax-exempt vehicle.

Further Information Available

Bar Charts and Performance Tables

The bar chart and performance table below for each fund are intended to indicate some of the risks of investing in a fund by showing changes in that fund’s performance over time. The performance table also shows:

•

how each fund’s performance over time compares with that of a broad measure of market performance, and

•

each fund’s returns before the deduction of taxes and returns after the deduction of certain taxes for Class A shares.

The charts and tables provide past performance information. Each fund’s past performance (before and after taxes) does not necessarily indicate how the fund will perform in the future. The performance information in the chart and table is based upon calendar year periods, while the performance information presented under the caption “Financial Highlights” and in the fund’s shareholder reports is based upon the fund’s fiscal year. Therefore, these performance results may differ.

Bar Charts. The bar chart shows changes over time in the annual total return of Class A shares for the past ten calendar years, and assumes the reinvestment of distributions. The charts and related notes do not take into account any sales charges (loads) that you may be required to pay upon purchase or redemption of a fund’s shares. If these sales charges were included, they would reduce the returns shown. The return of the fund’s other classes of shares will differ from the Class A share returns shown in that fund’s bar chart, depending upon the expenses of those classes.

MFS Alabama Municipal Bond Fund:

LOGO

The return for the six-month period ended June 30, 2008 was 0.30%. During the periods shown in the bar chart, the highest quarterly return was 5.18% (for the calendar quarter ended September 30, 2002) and the lowest quarterly return was (2.23)% (for the calendar quarter ended June 30, 2004).

MFS Arkansas Municipal Bond Fund:

LOGO

The return for the six-month period ended June 30, 2008 was 0.59%. During the periods shown in the bar chart, the highest quarterly return was 4.70% (for the calendar quarter ended September 30, 2002) and the lowest quarterly return was (2.19)% (for the calendar quarter ended June 30, 2004).

MFS California Municipal Bond Fund:

LOGO

The return for the six-month period ended June 30, 2008 was (0.31)%. During the periods shown in the bar chart, the highest quarterly return was 5.90% (for the calendar quarter ended September 30, 2002) and the lowest quarterly return was (2.56)% (for the calendar quarter ended June 30, 1999).

MFS Florida Municipal Bond Fund:

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The return for the six-month period ended June 30, 2008 was (0.42)%. During the periods shown in the bar chart, the highest quarterly return was 4.79% (for the calendar quarter ended September 30, 2002) and the lowest quarterly return was (2.25)% (for the calendar quarter ended June 30, 1999).

MFS Georgia Municipal Bond Fund:

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The return for the six-month period ended June 30, 2008 was 1.02%. During the periods shown in the bar chart, the highest quarterly return was 5.22% (for the calendar quarter ended September 30, 2002) and the lowest quarterly return was (2.42)% (for the calendar quarter ended June 30, 2004).

MFS Maryland Municipal Bond Fund:

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The return for the six-month period ended June 30, 2008 was 0.22%. During the periods shown in the bar chart, the highest quarterly return was 4.51% (for the calendar quarter ended September 30, 2002) and the lowest quarterly return was (2.24)% (for the calendar quarter ended June 30, 2004).

MFS Massachusetts Municipal Bond Fund:

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The return for the six-month period ended June 30, 2008 was 0.09%. During the periods shown in the bar chart, the highest quarterly return was 5.31% (for the calendar quarter ended September 30, 2002) and the lowest quarterly return was (2.28)% (for the calendar quarter ended June 30, 2004).

MFS Mississippi Municipal Bond Fund:

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The return for the six-month period ended June 30, 2008 was 0.65%. During the periods shown in the bar chart, the highest quarterly return was 4.85% (for the calendar quarter ended September 30, 2002) and the lowest quarterly return was (1.83)% (for the calendar quarter ended June 30, 2004).

MFS New York Municipal Bond Fund:

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The return for the six-month period ended June 30, 2008 was 0.16%. During the periods shown in the bar chart, the highest quarterly return was 5.08% (for the calendar quarter ended December 31, 2000) and the lowest quarterly return was (2.37)% (for the calendar quarter ended June 30, 2004).

MFS North Carolina Municipal Bond Fund:

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The return for the six-month period ended June 30, 2008 was (0.25)%. During the periods shown in the bar chart, the highest quarterly return was 4.87% (for the calendar quarter ended September 30, 2002) and the lowest quarterly return was (2.10)% (for the calendar quarter ended June 30, 2004).

MFS Pennsylvania Municipal Bond Fund:

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The return for the six-month period ended June 30, 2008 was 0.24%. During the periods shown in the bar chart, the highest quarterly return was 5.03% (for the calendar quarter ended September 30, 2002) and the lowest quarterly return was (2.26)% (for the calendar quarter ended June 30, 2004).

MFS South Carolina Municipal Bond Fund:

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The return for the six-month period ended June 30, 2008 was (0.01)%. During the periods shown in the bar chart, the highest quarterly return was 4.99% (for the calendar quarter ended September 30, 2002) and the lowest quarterly return was (2.38)% (for the calendar quarter ended June 30, 2004).

MFS Tennessee Municipal Bond Fund:

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The return for the six-month period ended June 30, 2008 was (0.17)%. During the periods shown in the bar chart, the highest quarterly return was 4.55% (for the calendar quarter ended September 30, 2002) and the lowest quarterly return was (2.09)% (for the calendar quarter ended June 30, 1999).

MFS Virginia Municipal Bond Fund:

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The return for the six-month period ended June 30, 2008 was 0.15%. During the periods shown in the bar chart, the highest quarterly return was 4.52% (for the calendar quarter ended September 30, 2002) and the lowest quarterly return was (2.02)% (for the calendar quarter ended June 30, 2004).

MFS West Virginia Municipal Bond Fund:

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The return for the six-month period ended June 30, 2008 was (0.37)%. During the periods shown in the bar chart, the highest quarterly return was 4.43% (for the calendar quarter ended September 30, 2002) and the lowest quarterly return was (2.34)% (for the calendar quarter ended June 30, 2004).

Performance Tables. The tables show how the average annual total returns of each class of each fund, before the deduction of taxes (“Returns Before Taxes”), compare to a broad measure of market performance, and assumes the deduction of the maximum applicable sales loads (initial sales charge and/or contingent deferred sales charge (CDSC), as applicable), and the reinvestment of distributions. In addition, for each fund’s Class A shares, the tables show Class A average annual total returns:

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after the deduction of taxes on distributions made on Class A shares, such as capital gains and income distributions (“Class A Shares’ Return After Taxes on Distributions”), and

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MFS Alabama Municipal Bond Fund: