Pioneer High Income Municipal Fund

Before you invest, you may want to review the fund’s prospectus, which contains more information about the fund and its risks. You can find the fund’s prospectus, statement of additional information and other information about the fund online at http://us.pioneerinvestments.com/misc/prospectus.jsp. You also can obtain this information at no cost by calling 1-800-225-6292 or by sending an email request to askpioneer@pioneerinvestments.com or by asking any financial intermediary that offers shares of the fund. The fund’s current prospectus and statement of additional information, dated December 31, 2010, and the independent registered public accounting firm’s report and financial statements in the fund’s annual report to shareholders dated August 31, 2010, are incorporated by reference into this summary prospectus.

Maximize total return through a combination of income that is exempt from regular federal income tax and capital appreciation.

This table describes the fees and expenses that you may pay if you buy and hold shares of the fund.

You may qualify for sales charge discounts if you or your family invest, or agree to invest in the future, at least $100,000 in Class A shares of the Pioneer funds. More information about these and other discounts is available from your investment professional and in the “Sales Charges” section of the prospectus beginning on page 29 and the “Sales Charges” section of the statement of additional information beginning on page 66.

This example is intended to help you compare the cost of investing in the fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the fund for the time periods shown and then, except as indicated, redeem all of your shares at the end of those periods. It also assumes that (a) your investment has a 5% return each year and (b) the fund’s total annual operating expenses remain the same except for year one (which considers the effect of the expense limitation). Although your actual costs may be higher or lower, based on these assumptions your costs would be:

The fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the fund’s performance. During the most recent fiscal year, the fund’s portfolio turnover rate was 15% of the average value of its portfolio.

Normally, the fund invests at least 80% of its net assets (plus the amount of borrowings, if any, for investment purposes) in debt securities and other obligations issued by or on behalf of states, counties, municipalities, territories and possessions of the United States and the District of Columbia and their

authorities, political subdivisions, agencies and instrumentalities, the interest on which is exempt from regular federal income tax (“municipal securities”).

The fund may invest in municipal securities with a broad range of maturities. Municipal securities with longer maturities are generally more volatile than other fixed income securities with shorter maturities. The fund may invest 25% or more of its assets in issuers in any one or more states or in the same economic sector or similar project type.

The fund primarily invests in “high yield” municipal obligations, commonly referred to as “junk bonds.” The fund may invest in securities in any rating category, including those in default.

Interest income from certain types of municipal obligations in which the fund may invest generally will be subject to the federal alternative minimum tax (AMT) for individuals. All distributions to corporate investors may also be subject to the AMT. The fund may not be suitable for investors subject to the AMT. The rate of interest paid on municipal securities normally is lower than the rate of interest paid on taxable securities.

The fund’s investments may have fixed or variable principal payments and all types of interest rate payment and reset terms, including fixed and floating rates, inverse floating rate, zero coupon, contingent, deferred and payment in kind and auction rate features.

The fund may use derivatives, such as synthetic municipal securities, inverse floating rate obligations and credit default swaps, for a variety of purposes, including: as a hedge against adverse changes in the market price of securities, interest rates or currency exchange rates; as a substitute for purchasing or selling securities; and to increase the fund’s return as a non-hedging strategy that may be considered speculative. The fund also may invest in subordinated securities and asset-backed securities, and may hold cash or other short-term investments.

The fund may invest up to 20% of its net assets in inverse floating rate obligations.

The fund may invest up to 20% of its net assets in taxable investments, including securities of other investment companies, commercial paper, U.S. government securities, U.S. or foreign bank instruments and repurchase agreements.

The adviser considers both broad economic factors and issuer specific factors in selecting investments. In assessing the appropriate maturity and rating weighting of the fund’s portfolio, the adviser considers a variety of factors that are expected to influence economic activity and interest rates. The adviser selects individual securities to buy and sell based upon such factors as a security’s yield, liquidity and rating, an assessment of credit quality, and issuer diversification.

You could lose money on your investment in the fund. As with any mutual fund, there is no guarantee that the fund will achieve its objective. Following is a summary description of principal risks of investing in the fund.

Market risk. The values of securities held by the fund may fall due to general market conditions, such as real or perceived adverse economic, political, or regulatory conditions, inflation, changes in interest or currency rates or adverse investor sentiment. Adverse market conditions may be prolonged and may not have the same impact on all types of securities. The values of securities may fall due to factors affecting a particular issuer, industry or the securities market as a whole. The recent global financial crisis has caused a significant decline in the value and liquidity of many securities, including securities held by the fund. In response to the crisis, the U.S. government and the Federal Reserve have taken steps to support financial markets. The withdrawal of this support could also negatively affect the value and liquidity of certain securities. In addition, legislation recently enacted in the U.S. calls for changes in many aspects of financial regulation. The impact of the legislation on the markets, and the practical implications for market participants, may not be known for some time. The fund may experience a substantial or complete loss on any individual security.

Interest rate risk. Interest rates may go up, causing the value of the fund’s investments to decline (this risk may be greater for securities with longer maturities).

Credit risk. If an issuer or guarantor of a security held by the fund or a counterparty to a financial contract with the fund defaults on its obligation to pay principal and/or interest, has its credit rating downgraded or is perceived to be less creditworthy, or the credit quality or value of any underlying assets declines, the value of your investment will decline. Junk bonds have a higher risk of default or are already in default and are considered speculative. Subordinated securities will be disproportionately affected by a default or downgrade.

Prepayment or call risk. During periods of declining interest rates, the issuer of a security (or borrowers in a pool of loans) may prepay principal earlier than scheduled, forcing the fund to reinvest in lower yielding securities. The fund also may lose any premium it paid on the security.

Extension risk. During periods of rising interest rates, the average life of certain types of securities may be extended because of slower than expected principal payments. This may lock in a below market interest rate, increase the security’s duration (the estimated period until the security is paid in full) and reduce the value of the security.

Liquidity risk. Some securities held by the fund may be difficult to sell, or illiquid, particularly during times of market turmoil. Illiquid securities also may be difficult to value. If the fund is forced to sell an illiquid asset to meet

redemption requests or other cash needs, the fund may be forced to sell at a loss.

High yield or “junk” bond risk. Debt securities that are below investment grade, called “junk bonds,” are speculative, have a higher risk of default or are already in default, tend to be less liquid and are more difficult to value than higher grade securities. Junk bonds tend to be volatile and more susceptible to adverse events and negative sentiments.

Portfolio selection risk. The adviser’s judgment about the quality, relative yield, relative value or market trends affecting a particular sector or region, market segment, security or about interest rates generally, may prove to be incorrect.

Municipal securities risk. The issuer of a municipal security may not be able to make timely payments because of economic, political or other developments that may adversely affect the issuer. To the extent the fund invests significantly in a single state or in securities the payments on which are dependent upon a single project or source of revenues, or that relate to a sector or industry, the fund will be more susceptible to associated risks and developments. Many states and municipalities, as the rest of the nation, have experienced a significant economic slowdown, resulting in decreased revenues and budget shortfalls, which may adversely affect the ability of issuers of municipal securities to make required payments, as well as the market value and marketability of municipal securities held by the fund. In addition, new federal or state legislation or other developments may adversely affect the tax-exempt status of securities held by the fund or the ability of municipalities to repay these obligations. The rate of interest paid on municipal securities normally is lower than the rate of interest paid on fully taxable securities. Some municipal securities, such as general obligation issues, are backed by the issuer’s taxing authority, while other municipal securities, such as revenue issues, are backed only by revenues from certain facilities or other sources and not by the issuer itself. To the extent that the fund invests in municipal securities whose issuers are located in the state of Texas, the fund will be more susceptible to economic, political and other developments that may adversely affect Texas issuers than are funds whose portfolios are more geographically diverse.

Synthetic municipal securities risk. The tax-exempt character of the interest paid on synthetic municipal securities is based on the tax-exempt income stream from the collateral. These securities are subject to the risk that income derived from synthetic municipal securities is deemed to be taxable.

Asset-backed securities risk. The value of asset-backed securities will be influenced by factors affecting the assets underlying such securities. As a result, during periods of declining asset value, difficult or frozen credit markets, swings in interest rates, or deteriorating economic conditions, asset-backed securities may decline in value, face valuation difficulties, become

more volatile and/or become illiquid. Additionally, during such periods and also under normal conditions, these securities are also subject to prepayment and call risk. Some of these securities may receive little or no collateral protection from the underlying assets and are thus subject to the risk of default. The structure of some of these securities may be complex and there may be less available information than for other types of debt securities. Upon the occurrence of certain triggering events or defaults, the fund may become the holder of underlying assets at a time when those assets may be difficult to sell or may be sold only at a loss.

Risks of subordinated securities. A holder of securities that are subordinated or “junior” to more senior securities of an issuer is entitled to payment after holders of more senior securities of the issuer. As a result, subordinated securities will be disproportionately adversely affected by a default or even a perceived decline in creditworthiness of the issuer, or, in the case of a pooled investment, issuers of underlying obligations.

Taxable investment risk. Although distributions of interest income from the fund’s tax-exempt securities are generally exempt from regular federal income tax, distributions from other sources, including capital gain distributions and any gains on the sale of your shares, are not. You should consult a tax adviser about whether an alternative minimum tax applies to you and about state and local taxes on your fund distributions.

Non-diversification risk. The fund is not diversified, which means that it can invest a higher percentage of its assets in the securities of any one issuer than a diversified fund. Being non-diversified may magnify the fund’s losses from adverse events affecting a particular issuer.

Market segment risk. To the extent the fund emphasizes, from time to time, investments in a market segment, the fund will be subject to a greater degree to the risks particular to that segment, and may experience greater market fluctuation than a fund without the same focus.

Derivatives risk. Using derivatives exposes the fund to additional risks, may increase the volatility of the fund’s net asset value and may not provide the result intended. Derivatives may have a leveraging effect on the fund’s portfolio. Changes in a derivative’s value may not correlate well with the referenced asset or metric. The fund also may have to sell assets at inopportune times to satisfy its obligations. Derivatives may be difficult to sell, unwind or value, and the counterparty may default on its obligations to the fund. Recent legislation calls for new regulation of the derivatives markets. The extent and impact of the regulation is not yet known and may not be known for some time. New regulation of derivatives may make them more costly, may limit their availability, or may otherwise adversely affect their value or performance.

Credit default swap risk. Credit default swap contracts, a type of derivative instrument, involve special risks and may result in losses to the fund. Credit

default swaps may in some cases be illiquid, and they increase credit risk since the fund has exposure to both the issuer of the referenced obligation and the counterparty to the credit default swap. The absence of a central exchange or market for swap transactions led, in some instances, to difficulties in trading and valuation, especially in the event of market disruptions. Recent legislation, noted above, will require most swaps to be executed through a centralized exchange or regulated facility and be cleared through a regulated clearinghouse. The swap market could be disrupted or limited as a result of this legislation, which could adversely affect the fund. Moreover, the establishment of a centralized exchange or market for swap transactions may not result in swaps being easier to trade or value.

Leveraging risk. When the fund engages in transactions that have a leveraging effect on the fund’s portfolio, the value of the fund will be more volatile and all other risks will tend to be compounded. This is because leverage generally magnifies the effect of any increase or decrease in the value of the fund’s underlying assets or creates investment risk with respect to a larger pool of assets than the fund would otherwise have. Engaging in such transactions may cause the fund to liquidate positions when it may not be advantageous to do so to satisfy its obligations or meet segregation requirements. In addition, certain of the fund’s investments may have embedded leverage.

Risk of increase in expenses. Your actual costs of investing in the fund may be higher than the expenses shown in “Annual fund operating expenses” for a variety of reasons. For example, expense ratios may be higher than those shown if overall net assets decrease. Net assets are more likely to decrease and fund expense ratios are more likely to increase when markets are volatile.

Please note that there are many other factors that could adversely affect your investment and that could prevent the fund from achieving its goals.

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 government agency.

The bar chart and table indicate the risks and volatility of an investment in the fund by showing how the fund has performed in the past. The bar chart shows changes in the performance of the fund’s Class A shares from calendar year to calendar year. The table shows the average annual total returns for each class of the fund over time and compares these returns to the returns of the Barclays Capital High Yield Municipal Bond Index, a broad-based measure of market performance that has characteristics relevant to the fund’s investment strategies. You can obtain updated performance information by visiting http://us.pioneerinvestments.com/performance or by calling 1-800-225-6292.

The fund’s past performance (before and after taxes) does not necessarily indicate how it will perform in the future.

The bar chart does not reflect any sales charge you may pay when you buy fund shares. If this amount was reflected, returns would be less than those shown.

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. Actual after-tax returns depend on the investor’s tax situation and may

differ from those shown. The after-tax returns shown are not relevant to investors who hold fund shares through tax-deferred arrangements such as 401(k) plans or individual retirement accounts. After-tax returns are shown only for Class A shares. After-tax returns for Class C and Class Y shares will vary.

You may purchase, exchange or sell (redeem) shares each day the New York Stock Exchange is open through your financial intermediary or, for accounts held directly with the fund, by contacting the fund’s transfer agent in writing or by telephone (Pioneer Investment Management Shareholder Services, Inc., P.O. Box 55014, Boston, MA 02205-5014, tel. 1-800-225-6292).

Your initial investment for Class A or Class C shares must be at least $1,000. Additional investments must be at least $100 for Class A shares and $500 for Class C shares. The initial investment for Class Y shares must be at least $5 million. This amount may be invested in one or more of the Pioneer mutual funds that currently offer Class Y shares. There is no minimum additional investment amount for Class Y shares.

Distributions designated by the fund as “exempt-interest dividends” are exempt from regular federal income tax but may be subject to state or local income taxes and may be tax preference items for purposes of the AMT. Distributions of the fund’s capital gains are generally subject to tax.

If you purchase the fund through a broker-dealer or other financial intermediary (such as a bank), the fund and its related companies may pay the intermediary for the sale of fund shares and related services. These payments may create a conflict of interest by influencing the broker-dealer or other intermediary and your salesperson or investment professional to recommend the fund over another investment. Ask your salesperson or investment professional or visit your financial intermediary’s website for more information.


(expenses that you pay each year as a percentage of the value of your investment)	Class A		Class C		Class Y
Management Fees		0.50%		0.50%		0.50%
Distribution and Service (12b-1) Fees		0.25%		1.00%		0.00%
Other Expenses		0.20%		0.19%		0.17%
Total Annual Fund Operating Expenses		0.95%		1.69%		0.67%
Less: Fee Waiver and Expense Reimbursement¹		–0.05%		0.00%		0.00%
Net Expenses¹		0.90%		1.69%		0.67%


	If you redeem your shares								If you do not redeem your shares
	Number of years you own your shares
	1		3		5		10		1		3		5		10
Class A	$	538	$	734	$	947	$	1,560	$	538	$	734	$	947	$	1,560
Class C		272		533		918		1,998		172		533		918		1,998
Class Y		68		214		373		835		68		214		373		835


Investment adviser		Pioneer Investment Management, Inc.

Portfolio management		Mr. Timothy Pynchon, lead portfolio manager (portfolio manager of the fund since 2006). Mr. David Eurkus, portfolio manager (portfolio manager of the fund since 2006).


Class A (PIMAX)		Class C (HICMX)		Class Y (HIMYX)


Summary Prospectus		December 31, 2010