Pioneer Bond Fund

Class A Shares (PIOBX)	Class C Shares (PCYBX)	Class K Shares (PBFKX)
Class R Shares (PBFRX)	Class Y Shares (PICYX)

Summary Prospectus

November 1, 2015

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 ask.pioneer@pioneerinvestments.com. The fund’s current prospectus and statement of additional information, dated November 1, 2015, and the independent registered public accounting firm’s report and financial statements in the fund’s annual report to shareholders dated June 30, 2015, are incorporated by reference into this summary prospectus.

Investment objectives

To provide current income from an investment grade portfolio with due regard to preservation of capital and prudent investment risk. The fund also seeks a relatively stable level of dividends; however, the level of dividends will be maintained only if consistent with preserving the investment grade quality of the portfolio.

Fees and expenses of the fund

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 54 and the “Sales charges” section of the statement of additional information beginning on page 65.

Summary Prospectus

Shareowner fees
(fees paid directly from your investment)	Class A	Class C	Class K	Class R	Class Y
Maximum sales charge (load) when you buy shares (as a percentage of offering price)	4.50%	None	None	None	None
Maximum deferred sales charge (load) (as a percentage of offering price or the amount you receive when you sell shares, whichever is less)	None¹	1%	None	None	None

Annual fund operating expenses
(expenses that you pay each year as a percentage of the value of your investment)	Class A	Class C	Class K	Class R	Class Y
Management Fees	0.40%	0.40%	0.40%	0.40%	0.40%
Distribution and Service (12b-1) Fees	0.25%	1.00%	0.00%	0.50%	0.00%
Other Expenses	0.28%	0.23%	0.07%	0.31%	0.18%
Total Annual Fund Operating Expenses	0.93%	1.63%	0.47%	1.21%	0.58%
Less: Fee Waiver and Expense Reimbursement²	–0.08 %	0.00%	0.00%	-0.11%	0.00%
Net Expenses²	0.85%	1.63%	0.47%	1.10%	0.58%

Class A purchases of $500,000 or more that are not subject to an initial sales charge may be subject to a contingent deferred sales charge of 1%. See “Sales charges.”

The fund’s investment adviser has contractually agreed to limit ordinary operating expenses (ordinary operating expenses means all fund expenses other than extraordinary expenses, such as litigation, taxes, brokerage commissions and acquired fund fees and expenses) to the extent required to reduce fund expenses to 0.85% and 1.10% of the average daily net assets attributable to Class A and Class R shares, respectively. These expense limitations are in effect through November 1, 2017. There can be no assurance that the adviser will extend the expense limitations beyond such times. While in effect, the arrangement may be terminated for a class only by agreement of the adviser and the Board of Trustees.

Example

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:

	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	$533	$725	$934	$1,535	$533	$725	$934	$1,535
Class C	266	514	887	1,933	166	514	887	1,933
Class K	48	151	263	591	48	151	263	591
Class R	112	373	654	1,456	112	373	654	1,456
Class Y	59	186	324	726	59	186	324	726

Portfolio turnover

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 81% of the average value of its portfolio.

Principal investment strategies

Normally, the fund invests at least 80% of its net assets (plus the amount of borrowings, if any, for investment purposes) in debt securities issued or guaranteed by the U.S. government, its agencies and instrumentalities, investment grade debt securities (including convertible debt) of corporate or other issuers and cash, cash equivalents and other short-term holdings. Derivative instruments that provide exposure to such securities or have similar economic characteristics may be used to satisfy the fund’s 80% policy.

The fund may invest a substantial portion of its assets in mortgage-related securities, including “sub-prime” mortgages, and asset-backed securities. The fund also may invest a portion of its assets in subordinated debt securities, municipal securities, preferred securities, and event-linked bonds and other insurance-linked securities.

The fund may invest up to 20% of its net assets in debt securities rated below investment grade or, if unrated, of equivalent credit quality as determined by the adviser (known as “junk bonds”), including securities that are in default. The fund may invest up to 15% of its total assets in securities of non-U.S. issuers, including up to 5% of its total assets in securities of emerging market issuers.

Summary Prospectus

The fund may invest in securities with a broad range of maturities, and maintains an average portfolio maturity which varies based upon the judgment of the fund's investment adviser. The fund's investments may have fixed or variable principal payments and all types of interest rate payment and reset terms, including fixed rate, floating rate, inverse floating rate, zero coupon, when-issued, delayed delivery, to be announced and forward commitment, contingent, deferred and payment in kind and auction rate features. The fund's investments may include instruments that allow for balloon payments or negative amortization payments.

The fund may, but is not required to, use derivatives such as credit default swaps and bond and interest rate futures. The fund may use derivatives for a variety of purposes, including: in an attempt to hedge against adverse changes in the market price of securities, interest rates or currency exchange rates; as a substitute for purchasing or selling securities; to attempt to increase the fund's return as a non-hedging strategy that may be considered speculative; to manage portfolio characteristics; and as a cash flow management technique. The fund may choose not to make use of derivatives for a variety of reasons, and any use may be limited by applicable law and regulations. The fund may hold cash or other short-term investments.

The adviser considers both broad economic and issuer specific factors in selecting investments. In assessing the appropriate maturity, credit quality and sector 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 sector and issuer diversification.

Principal risks of investing in the fund

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 objectives.

Market risk. The values of securities held by the fund may go up or down, sometimes rapidly or unpredictably, due to general market conditions, such as real or perceived adverse economic, political, or regulatory conditions, inflation, changes in interest or currency rates, lack of liquidity in the bond markets or adverse investor sentiment. In the past several years, financial markets, such as those in the United States, Europe, Asia and elsewhere, have experienced increased volatility, depressed valuations, decreased

liquidity and heightened uncertainty. Governmental and non-governmental issuers have defaulted on, or been forced to restructure, their debts. These conditions may continue, recur, worsen or spread. The U.S. government and the Federal Reserve, as well as certain foreign governments and their central banks, have taken steps to support financial markets, including by keeping interest rates at historically low levels. This and other government intervention may not work as intended, particularly if the efforts are perceived by investors as being unlikely to achieve the desired results. The Federal Reserve recently has reduced its market support activities. Further reduction or withdrawal of Federal Reserve or other U.S. or non-U.S. governmental or central bank support, including interest rate increases, could negatively affect financial markets generally, increase market volatility and reduce the value and liquidity of securities in which the fund invests. Policy and legislative changes in the U.S. and in other countries are affecting many aspects of financial regulation, and may in some instances contribute to decreased liquidity and increased volatility in the financial markets. The impact of these changes on the markets, and the practical implications for market participants, may not be fully known for some time. Economies and financial markets throughout the world are becoming increasingly interconnected. As a result, whether or not the fund invests in securities of issuers located in or with significant exposure to countries experiencing economic and financial difficulties, the value and liquidity of the fund’s investments may be negatively affected. The fund may experience a substantial or complete loss on any individual security or derivative position.

Interest rate risk. Interest rates may go up, causing the value of the fund's investments to decline (this risk generally will be greater for securities with longer maturities or durations). Interest rates in the U.S. recently have been historically low, so the fund faces a heightened risk that interest rates may rise. A general rise in interest rates may cause investors to move out of fixed income securities on a large scale, which could adversely affect the price and liquidity of fixed income securities and could also result in increased redemptions from the fund.

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 typically decline.

Summary Prospectus

Prepayment or call risk. Many issuers have a right to prepay their securities. If interest rates fall, an issuer may exercise this right. If this happens, the fund will not benefit from the rise in market price that normally accompanies a decline in interest rates, and will be forced to reinvest prepayment proceeds at a time when yields on securities available in the market are lower than the yield on the prepaid security. 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 and reduce the value of the security.

Liquidity risk. Some securities and derivatives held by the fund may be impossible or difficult to purchase, sell or unwind, particularly during times of market turmoil. An instrument’s liquidity may be affected by reduced trading volume, a relative lack of market makers or legal restrictions, and illiquid securities and derivatives also may be difficult to value. Liquidity risk may be magnified in a rising interest rate environment. If the fund is forced to sell an illiquid asset or unwind a derivatives position to meet redemption requests or other cash needs, the fund may be forced to sell at a loss.

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.

U.S. Treasury obligations risk. The market value of direct obligations of the U.S. Treasury may vary due to changes in interest rates. In addition, changes to the financial condition or credit rating of the U.S. government may cause the value of the fund’s investments in obligations issued by the U.S. Treasury to decline.

U.S. government agency obligations risk. The fund invests in obligations issued by agencies and instrumentalities of the U.S. government. Government-sponsored entities such as Federal National Mortgage Association (“FNMA”), Federal Home Loan Mortgage Corporation (“FHLMC”) and the Federal Home Loan Banks (“FHLBs”), although chartered or sponsored by Congress, are not funded by congressional appropriations and the debt and mortgage-backed securities issued by them are neither guaranteed nor issued by the U.S. government. Such debt

and mortgage-backed securities are subject to the risk of default on the payment of interest and/or principal, similar to debt of private issuers. Although the U.S. government has provided financial support to FNMA and FHLMC in the past, there can be no assurance that it will support these or other government-sponsored entities in the future.

Mortgage-related and asset-backed securities risk. The value of mortgage-related and asset-backed securities will be influenced by factors affecting the housing market and 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, mortgage-related and asset-backed securities may decline in value, face valuation difficulties, become more volatile and/or become illiquid. Mortgage-backed securities tend to be more sensitive to changes in interest rate than other types of debt securities. These securities are also subject to prepayment and extension risks. 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 risk of such defaults is generally higher in the case of mortgage-backed investments that include so-called “sub-prime” mortgages. 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 instruments that allow for balloon payments or negative amortization payments. Certain debt instruments allow for balloon payments or negative amortization payments. Such instruments permit the borrower to avoid paying currently a portion of the interest accruing on the instrument. While these features make the debt instrument more affordable to the borrower in the near term, they increase the risk that the borrower will be unable to make the resulting higher payment or payments that become due at the maturity of the loan.

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. These risks are more pronounced for securities that are already in default.

Summary Prospectus

Risks of investing in floating rate loans. Floating rate loans and similar investments may be illiquid or less liquid than other investments and difficult to value. The value of collateral, if any, securing a floating rate loan can decline or may be insufficient to meet the issuer’s obligations or may be difficult to liquidate. No active trading market may exist for many floating rate loans, and many loans are subject to restrictions on resale. Market quotations for these securities may be volatile and/or subject to large spreads between bid and ask prices. Any secondary market may be subject to irregular trading activity and extended trade settlement periods.

Risks of investing in insurance-linked securities. The return of principal and the payment of interest on “event-linked” bonds and other insurance-linked securities are contingent on the non-occurrence of a pre-defined “trigger” event, such as a hurricane or an earthquake of a specific magnitude or other event that leads to physical or economic loss. If a trigger event, as defined within the terms of an event-linked bond, involves losses or other metrics exceeding a specific magnitude in the geographic region and time period specified, the fund may lose a portion or all of its accrued interest and/or principal invested in the event-linked bond. In addition to the specified trigger events, event-linked bonds may expose the fund to other risks, including but not limited to issuer (credit) default, adverse regulatory or jurisdictional interpretations and adverse tax consequences. Certain insurance-linked securities may have limited liquidity, or may be illiquid. The fund has limited transparency into the individual contracts underlying certain insurance-linked securities, which may make the risk assessment of such securities more difficult. Certain insurance-linked securities may be difficult to value.

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. Subordinated securities are more likely to suffer a credit loss than non-subordinated securities of the same issuer, any loss incurred by the subordinated securities is likely to be proportionately greater, and any recovery of interest or principal may take more time. As a result, even a perceived decline in creditworthiness of the issuer is likely to have a greater impact on them.

Municipal securities risk. The municipal bond market can be susceptible to unusual volatility, particularly for lower-rated and unrated securities. Liquidity can be reduced unpredictably in response to overall economic

conditions or credit tightening. Municipal issuers may be adversely affected by rising health care costs, increasing unfunded pension liabilities, and by the phasing out of federal programs providing financial support. Unfavorable conditions and developments relating to projects financed with municipal securities can result in lower revenues to issuers of municipal securities, potentially resulting in defaults. Issuers often depend on revenues from these projects to make principal and interest payments. The value of municipal securities can also be adversely affected by changes in the financial condition of one or more individual municipal issuers or insurers of municipal issuers, regulatory and political developments, tax law changes or other legislative actions, and by uncertainties and public perceptions concerning these and other factors. Municipal issuers may be more susceptible to downgrades or defaults during recessions or similar periods of economic stress. In recent periods, an increasing number of municipal issuers in the United States have defaulted on obligations and commenced insolvency proceedings. Financial difficulties of municipal issuers may continue or get worse. 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.

Risks of zero coupon bonds, payment in kind, deferred and contingent payment securities. These securities may be more speculative and may fluctuate more in value than securities which pay income periodically and in cash. In addition, although the fund receives no periodic cash payments on such securities, the fund is deemed for tax purposes to receive income from such securities, which applicable tax rules require the fund to distribute to shareholders. Such distributions may be taxable when distributed to shareholders.

Risks of investing in when-issued, delayed delivery, to be announced and forward commitment transactions. The market value of these transactions may increase or decrease as a result of changes in interest rates. These transactions involve risk of loss if the value of the underlying security changes unfavorably before the settlement date or if the assets set aside to pay for these securities decline in value prior to the settlement date. Therefore, these transactions may have a leveraging effect on the fund, making the value of an investment in the fund more volatile and increasing the fund’s overall investment exposure. There is

Summary Prospectus

also a risk that the other party to the transaction will default on its obligation to purchase or sell the security, which may result in the fund missing the opportunity to obtain a favorable price or yield elsewhere.

Risks of non-U.S. investments. Investing in non-U.S. issuers, or in U.S. issuers that have significant exposure to foreign markets, may involve unique risks compared to investing in securities of U.S. issuers. These risks are more pronounced for issuers in emerging markets or to the extent that the fund invests significantly in one region or country. These risks may include different financial reporting practices and regulatory standards, less liquid trading markets, extreme price volatility, currency risks, changes in economic, political, regulatory and social conditions, sustained economic downturns, financial instability, tax burdens, and investment and repatriation restrictions. Lack of information and less market regulation also may affect the value of these securities. Withholding and other non-U.S. taxes may decrease the fund’s return. Non-U.S. issuers may be located in parts of the world that have historically been prone to natural disasters. Investing in depositary receipts is subject to many of the same risks as investing directly in non-U.S. issuers. Depositary receipts may involve higher expenses and may trade at a discount (or premium) to the underlying security.

Risks of convertible securities. The market values of convertible securities tend to decline as interest rates increase and, conversely, to increase as interest rates decline. A downturn in equity markets may cause the price of convertible securities to decrease relative to other fixed income securities.

Preferred stocks risk. Preferred stocks may pay fixed or adjustable rates of return. Preferred stocks are subject to issuer-specific and market risks applicable generally to equity securities. In addition, a company’s preferred stocks generally pay dividends only after the company makes required payments to holders of its bonds and other debt. Thus, the value of preferred stocks will usually react more strongly than bonds and other debt to actual or perceived changes in the company’s financial condition or prospects. The market value of preferred stocks generally decreases when interest rates rise. Preferred stocks of smaller companies may be more vulnerable to adverse developments than preferred stocks of larger companies.

Derivatives risk. Using swaps, futures and other derivatives can increase fund losses and reduce opportunities for gains when market prices, interest rates or the derivative instruments themselves behave in a way not anticipated by the fund. Using derivatives 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. Some derivatives have the potential for unlimited loss, regardless of the size of the fund’s initial investment. 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. The U.S. government is in the process of adopting and implementing regulations governing derivatives markets, including mandatory clearing of certain derivatives, margin and reporting requirements. The ultimate impact of the regulations remains unclear. Additional regulation of derivatives may make them more costly, may limit their availability, may disrupt markets 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 the issuer of the referenced obligation and either the counterparty to the credit default swap or, if it is a cleared transaction, the brokerage firm through which the trade was cleared and the clearing organization that is the counterparty to that trade.

Risks of investing in inverse floating rate obligations. The interest rate on inverse floating rate obligations will generally decrease as short-term interest rates increase, and increase as short-term rates decrease. Due to their leveraged structure, the sensitivity of the market value of an inverse floating rate obligation to changes in interest rates is generally greater than a comparable long-term bond issued by the same issuer and with similar credit quality, redemption and maturity provisions. Inverse floating rate obligations may be volatile and involve leverage risk.

Leveraging risk. The value of your investment may be more volatile and other risks tend to be compounded if the fund borrows or uses derivatives or other investments that have embedded leverage. Leverage generally magnifies the effect of any increase or decrease in the value of the fund's underlying assets and creates a risk of loss of value on a larger pool of

Summary Prospectus

assets than the fund would otherwise have, potentially resulting in the loss of all assets. 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.

Repurchase agreement risk. In the event that the other party to a repurchase agreement defaults on its obligations, the fund may encounter delay and incur costs before being able to sell the security. Such a delay may involve loss of interest or a decline in price of the security. In addition, if the fund is characterized by a court as an unsecured creditor, it would be at risk of losing some or all of the principal and interest involved in the transaction.

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.

Valuation risk. The sales price the fund could receive for any particular portfolio investment may differ from the fund’s last valuation of the investment, particularly for illiquid securities and securities that trade in thin or volatile markets or that are valued using a fair value methodology. Investors who purchase or redeem fund shares on days when the fund is holding fair-valued securities may receive fewer or more shares or lower or higher redemption proceeds than they would have received if the fund had not fair-valued the security or had used a different valuation methodology.

Expense risk. 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 fund's past performance

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 Aggregate 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 https://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.

Annual return Class A shares (%)

(Year ended December 31)

For the period covered by the bar chart:

The highest calendar quarterly return was 6.84% (07/01/2009 to 09/30/2009).
The lowest calendar quarterly return was -3.05% (10/01/2008 to 12/31/2008).

At September 30, 2015, the year-to-date return was 0.16%.

Summary Prospectus

Average annual total return (%)

(for periods ended December 31, 2014)

	1 Year	5 Years	10 Years	Since Inception	Inception Date
Class A					10/31/78
Return before taxes	1.18	4.90	4.88	7.39
Return after taxes on distributions	-0.34	3.25	3.12	4.09
Return after taxes on distributions and sale of shares	0.74	3.14	3.09	4.06
Class C†	5.06	4.93	4.42	4.74	1/31/96
Class K	6.14	N/A	N/A	3.53	12/20/12
Class R	5.65	5.47	5.00	5.32	4/1/03
Class Y	6.19	6.11	5.65	6.21	9/20/01
Barclays Capital Aggregate Bond Index (reflects no deduction for fees, expenses or taxes)	5.97	4.45	4.71	7.94	10/31/78

†	The performance of Class C shares does not reflect the 1% front-end sales charge in effect prior to February 1, 2004. If you paid a 1% sales charge, your returns would be lower than those shown above.

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, Class K, Class R and Class Y shares will vary.

Management

Investment adviser	Pioneer Investment Management, Inc.
Portfolio management	Kenneth J. Taubes. Executive Vice President and Chief Investment Officer, U.S. of Pioneer (portfolio manager of the fund since 1998), and Charles Melchreit, Senior Vice President of Pioneer (portfolio manager of the fund since 2012).

Purchase and sale of fund shares

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 in writing or by telephone, Pioneer Funds, 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 K shares must be at least $5 million. 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 K or Class Y shares. There is no minimum investment amount for Class R shares.

Tax information

The fund intends to make distributions that may be taxed as ordinary income or capital gains.

Payments to broker-dealers and other financial intermediaries

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 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.