Mutual Fund Summary Prospectus (497k)

Pioneer International Value Fund

Class A Shares (PIIFX)	Class B Shares (PBIFX)	Class C Shares (PCITX)
Class Y Shares (INVYX)

Summary Prospectus

April 1, 2014

    

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 [e-mail]. The fund’s current prospectus and statement of additional information, dated April 1, 2014, and the independent registered public accounting firm’s report and financial statements in the fund’s annual report to shareholders dated November 30, 2013, are incorporated by reference into this summary prospectus.

Investment objective

Long-term capital growth.

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 $50,000 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 33 and the “Sales charges” section of the statement of additional information beginning on page 53.

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Summary Prospectus

Shareowner fees
(fees paid directly from your investment)	Class A	Class B	Class C	Class Y
Maximum sales charge (load) when you buy shares (as a percentage of offering price)	5.75%	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)	None	4%	1%	None

Annual fund operating expenses
(expenses that you pay each year as a percentage of the value of your investment)	Class A	Class B	Class C	Class Y
Management Fees	0.85%	0.85%	0.85%	0.85%
Distribution and Service (12b-1) Fees	0.25%	1.00%	1.00%	0.00%
Other Expenses	0.59%	1.45%	0.56%	0.19%
Total Annual Fund Operating Expenses	1.69%	3.30%	2.41%	1.04%
Less: Fee Waiver and Expense Reimbursement 1	–0.24%	–0.95%	–0.06%	0.00%
Net Expenses 1	1.45%	2.35%	2.35%	1.04%

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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 1.45%, 2.35% and 2.35% of the average daily net assets attributable to Class A, Class B and Class C shares, respectively. These expense limitations are in effect through April 1, 2015. There can be no assurance that the adviser will extend the expense limitations beyond such time. Net expenses for a Class may exceed the applicable expense limitation to the extent that the fund incurs excluded expenses. While in effect, the arrangement may be terminated for a class only by agreement of the adviser and the Board of Trustees.

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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	$714	$1,055	$1,419	$2,439		$714	$1,055	$1,419	$2,439
Class B	638	1,227	1,740	3,158		238	927	1,640	3,158
Class C	338	746	1,280	2,742		238	746	1,280	2,742
Class Y	106	331	574	1,271		106	331	574	1,271

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 101% of the average value of its portfolio.

Principal investment strategies

Normally, the fund invests at least 80% of its total assets in equity securities of non-U.S. issuers. These issuers may be located in both developed and emerging markets. Under normal circumstances, the fund's assets will be invested in securities of companies domiciled in at least three different foreign countries. Generally, the fund's investments in any country are limited to 25% or less of its total assets. However, from time to time, the fund may invest more than 25% of its assets in issuers organized in Japan or the United Kingdom or in securities quoted or denominated in the Japanese yen, the British pound and the euro.

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Summary Prospectus

The fund may invest without limitation in securities of issuers located in countries with emerging economies or securities markets, but will not invest more than 25% of its total assets in securities of issuers located in any one such country. Emerging economies or securities markets generally will include, but not be limited to, countries included in the Morgan Stanley Capital International (MSCI) Emerging & Frontier Markets Index.

For purposes of the fund's investment policies, equity securities include common stocks and other equity instruments, such as exchange-traded funds (ETFs) that invest primarily in equity securities, depositary receipts, equity interests in real estate investment trusts (REITs), warrants, rights and preferred shares. The fund may invest in initial public offerings of equity securities. The fund may also purchase and sell forward foreign currency exchange contracts in non-U.S. currencies in connection with its investments, including as a means of managing relative currency exposure.

The fund may invest up to 20% of its total assets in debt securities of U.S. and non-U.S. issuers. The fund may invest up to 5% of its net assets in below investment grade debt securities (known as “junk bonds”), including below investment grade convertible debt securities and securities of issuers that are in default.

The fund may, but is not required to, use derivatives. The fund may use derivatives, including forward foreign currency exchange contracts, for a variety of purposes, including; in an attempt to hedge against adverse changes in the market prices 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; and to manage portfolio characteristics. 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 also may hold cash or other short-term instruments.

The fund's investment adviser uses a value approach to select the fund's investments. The adviser seeks to identify securities that are selling at reasonable prices or substantial discounts to their underlying values. The adviser evaluates a security's potential value, including the attractiveness of its market valuation, based on the company's assets and prospects for earnings and revenue growth, employing a bottom-up analytical style. In making that assessment, the adviser employs fundamental research and

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an evaluation of the issuer based on its financial statements and operations. The adviser focuses on the quality and price of individual issuers and securities.

The adviser generally sells a portfolio security when it believes that the security’s market value reflects its intrinsic value. The adviser makes that determination based upon the same criteria it uses to select portfolio securities.

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 objective.

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. 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 stock market may perform poorly relative to other investments (this risk may be greater in the short term). High public debt in the U.S. and other countries creates ongoing and systemic market risks and policymaking uncertainty. The financial crisis that began in 2008 has caused a significant decline in the value and liquidity of many securities worldwide. Governmental and non-governmental issuers have defaulted on, or been forced to restructure, their debts, and many other issuers have faced difficulties obtaining credit. These market conditions may continue, worsen or spread, including in the U.S., Europe and beyond. Further defaults or restructurings by governments and others of their debt could have additional adverse effects on economies, financial markets and asset valuations around the world. In response to the crisis, the U.S. and other governments and the Federal Reserve and certain foreign central banks have taken steps to support financial markets, including by keeping interest rates at historically low levels. More recently, the Federal Reserve has reduced its market support activities. Further reduction or withdrawal of this support, failure of efforts in response to the crisis, or investor perception that these efforts are not succeeding could negatively affect financial markets generally as well as increase market volatility and reduce the value and liquidity of certain securities. Whether or not the fund invests in securities of issuers located

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Summary Prospectus

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. In addition, policy and legislative changes in the U.S. and in other countries are affecting many aspects of financial regulation. The impact of these changes on the markets, and the practical implications for market participants, may not be fully known for some time. The fund may experience a substantial or complete loss on any individual security or derivative position.

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.

Geographic focus risk. To the extent that the fund invests from time to time more than 25% of its assets in issuers organized or located in a particular geographic region, including but not limited to issuers organized or located in Japan or the United Kingdom or in securities quoted or denominated in the Japanese yen, the British pound and the euro, the fund may be particularly affected by adverse securities markets, exchange rates and social, political, regulatory or economic events which may occur in those countries or regions.

Currency risk. Because the fund may invest in non-U.S. currencies, securities denominated in non-U.S. currencies, and other currency-related investments, the fund is subject to currency risk, meaning that the fund could experience losses based on changes in the exchange rate between non-U.S. currencies and the U.S. dollar or as a result of currency

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conversion costs. Currency exchange rates can be volatile, and are affected by factors such as general economic conditions, the actions of the U.S. and foreign governments or central banks, the imposition of currency controls and speculation.

Forward foreign currency transactions risk. To the extent that the fund enters into forward foreign currency transactions, it may not fully benefit from or may lose money on the transactions if changes in currency rates do not occur as anticipated or do not correspond accurately to changes in the value of the fund's holdings, or if the counterparty defaults. Such transactions may also prevent the fund from realizing profits on favorable movements in exchange rates. Risk of counterparty default is greater for counterparties located in emerging markets. The fund's ability to use forward foreign currency transactions successfully depends on a number of factors, including the forward foreign currency transactions being available at prices that are not too costly, the availability of liquid markets, and the adviser’s judgment regarding the direction of changes in currency exchange rates.

Value style risk. The prices of securities the adviser believes are undervalued may not appreciate as expected or may go down. Value stocks may fall out of favor with investors and underperform the overall equity market.

Portfolio selection risk. The adviser's judgment about a particular security or issuer, or about the economy or a particular sector, region or market segment, or about an investment strategy, may prove to be incorrect.

Small and mid-size companies risk. Compared to large companies, small- and mid-size companies, and the market for their equity securities, may be more sensitive to changes in earnings results and investor expectations, have more limited product lines and capital resources, experience sharper swings in market values, have limited liquidity, be harder to value or to sell at the times and prices the adviser thinks appropriate, and offer greater potential for gain and loss.

Risks of investments in REITs. Investments in real estate securities are affected by economic conditions, interest rates, governmental actions and other factors. In addition, investing in REITs involves unique risks. They are significantly affected by the market for real estate and are dependent upon management skills and cash flow. REITs may have lower trading volumes

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Summary Prospectus

and may be subject to more abrupt or erratic price movements than the overall securities markets. Mortgage REITs are particularly subject to interest rate and credit risks. In addition to its own expenses, the fund will indirectly bear its proportionate share of any management and other expenses paid by REITs in which it invests. Many real estate companies, including REITs, utilize leverage.

Risks of warrants and rights. If the price of the underlying stock does not rise above the exercise price before the warrant expires, the warrant generally expires without any value and the fund loses any amount it paid for the warrant. The failure to exercise subscription rights to purchase common shares would result in the dilution of the fund’s interest in the issuing company.

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.

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.

Debt securities risk. Factors that could contribute to a decline in the market value of debt securities in the fund include rising interest rates, if the issuer or other obligor of a security held by the fund fails to pay principal and/or interest, otherwise defaults or has its credit rating downgraded or is perceived to be less creditworthy or the credit quality or value of any underlying assets declines. Junk bonds involve greater risk of loss, are subject to greater price volatility and are less liquid, especially during periods of economic uncertainty or change, than higher quality debt

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securities; they may also be more difficult to value. Junk bonds have a higher risk of default or are already in default and are considered speculative.

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 stock index futures and options 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. New regulations are changing the derivatives markets. The regulations may make using derivatives more costly, may limit their availability, or may otherwise adversely affect their value or performance. For derivatives that are required to be traded through a clearinghouse or exchange, the fund also will be exposed to the credit risk of the clearinghouse and the broker that submits trades for the fund. It is possible that certain derivatives that are required to be cleared, such as certain swap contracts, will not be accepted for clearing. In addition, regulated trading facilities for swap contracts are relatively new; they may not function as intended, which could impair the ability to enter into swap contracts. The extent and impact of the new regulations are not yet fully known and may not be for some time.

Risks of initial public offerings. Companies involved in initial public offerings (IPOs) generally have limited operating histories, and prospects for future profitability are uncertain. Information about the companies may be available for very limited periods. The market for IPO issuers has been volatile, and share prices of newly public companies have fluctuated significantly over short periods of time. Further, stocks of newly-public

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Summary Prospectus

companies may decline shortly after the IPO. There is no assurance that the fund will have access to IPOs. The purchase of IPO shares may involve high transaction costs.

Portfolio turnover risk. If the fund does a lot of trading, it may incur additional operating expenses, which would reduce performance. A higher level of portfolio turnover may also cause shareholders to incur a higher level of taxable income or capital gains.

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, such as ETFs, that have embedded leverage. 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, 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.

Risks of investment in other funds. Investing in other investment companies, including exchange-traded funds (ETFs), subjects the fund to the risks of investing in the underlying securities or assets held by those funds. When investing in another fund, the fund will bear a pro rata portion of the underlying fund’s expenses, in addition to its own expenses.

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

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returns for each class of the fund over time and compares these returns to the returns of the Morgan Stanley Capital International (MSCI) Europe, Australasia and Far East (EAFE) ND 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.

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Summary Prospectus

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 25.10% (04/01/2009 to 06/30/2009).
The lowest calendar quarterly return was –21.25% (10/01/2008 to 12/31/2008).

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Average annual total return (%)

(for periods ended December 31, 2013)

	1 Year	5 Years	10 Years	Since Inception	Inception Date
Class A					3/25/93
Return before taxes	12.97	8.98	4.67	4.36
Return after taxes on distributions	11.91	8.58	4.54	3.51
Return after taxes on distributions and sale of shares	7.34	7.01	3.80	3.21
Class B	14.79	9.30	4.32	1.83	4/4/94
Class C†	18.83	9.29	4.35	1.36	1/31/96
Class Y	20.33	N/A	N/A	12.84	4/15/09
Morgan Stanley Capital International (MSCI) Europe, Australasia and Far East (EAFE) ND Index (reflects no deduction for fees, expenses or taxes)*	22.78	12.44	6.91	6.33	3/31/93**

†	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.
*	Index values are calculated using net returns. Net returns approximate the minimum possible dividend reinvestment—the dividend is reinvested after deduction of withholding tax, applying the highest rate applicable to non-resident institutional investors who do not benefit from double taxation treaties.
**	Index comparison begins on March 31, 1993

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 B, Class C and Class Y shares will vary.

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Summary Prospectus

Management

Investment adviser	Pioneer Investment Management, Inc.
Portfolio management	Marco Pirondini, head of equities, U.S. and executive vice president of Pioneer (portfolio manager of the fund since 2010); Andrea Salvatori, head of global emerging markets & Latin American equities and senior vice president at Pioneer (portfolio manager of the fund since 2008); and Madelynn M. Matlock 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’s transfer agent in writing or by telephone (Pioneer Investment Management Shareholder Services, Inc., P.O. Box 55014, Boston, MA 02205-5014, tel. [phone]).

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. Effective December 31, 2009, Class B shares are no longer offered to new or existing shareholders, except for reinvestment of dividends and/or capital gains distributions and exchanges for Class B shares of other Pioneer funds.

Tax information

The fund intends to make distributions that may be taxed as ordinary income, qualified dividend 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.

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Notes

    

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23456-03-0414