Pioneer      Growth    Opportunities    Fund   

Class A Shares (PGOFX)	Class B Shares (GOFBX)	Class C Shares (GOFCX)
Class R Shares (PGRRX)	Class Y Shares (GROYX)

Summary Prospectus May 1, 2011

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. The fund’s current prospectus and statement of additional information, dated May 1, 2011, and the independent registered public accounting firm’s report and financial statements in the fund’s annual report to shareholders dated December 31, 2010, are incorporated by reference into this summary prospectus.

Investment objectiveGrowth of capital.Fees and expenses of the fundThis 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 29 and the “Sales charges” section of the statement of additional information beginning on page 59.

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Summary Prospectus

Shareowner fees
(fees paid directly from your investment)	Class A	Class B	Class C	Class R	Class Y
Maximum sales charge (load) when you buy shares (as a percentage of offering price)	5.75%	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)	None	4%	1%	None	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 R	Class Y
Management Fees	0.65%	0.65%	0.65%	0.65%	0.65%
Distribution and Service (12b-1) Fees	0.25%	1.00%	1.00%	0.50%	0.00%
Other Expenses	0.39%	0.80%	0.61%	0.40%	0.11%
Total Annual Fund Operating Expenses	1.29%	2.45%	2.26%	1.55%	0.76%

ExampleThis 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. 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	$699	$960	$1,242	$2,042	$699	$960	$1,242	$2,042
Class B	648	1,064	1,406	2,499	248	764	1,306	2,499
Class C	329	706	1,210	2,595	229	706	1,210	2,595
Class R	158	490	845	1,845	158	490	845	1,845
Class Y	78	243	422	942	78	243	422	942

Portfolio turnoverThe 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

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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 114% of the average value of its portfolio.Principal investment strategiesThe fund invests primarily in equity securities of companies that the fund’s investment adviser considers to be reasonably priced or undervalued, with above average growth potential. For purposes of the fund’s investment policies, equity securities include common stocks, debt convertible to equity securities 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 stocks.The fund may invest in securities of any market capitalization, although the fund may invest a significant portion of its assets in equity securities of small companies. The fund defines small companies as those within the market capitalization range of the Russell 2000 Growth Index (approximately $1.6 billion to $5.6 billion as of March 31, 2011). The size of the companies in the index changes constantly with market conditions and the composition of the index. The fund may continue to hold a security if its market capitalization changes after investment.The fund may invest up to 20% of its total assets in debt securities of U.S. issuers. Generally the fund acquires debt securities that are investment grade, but the fund may invest up to 5% of its net assets in below investment grade debt securities (known as “junk bonds”), and below investment grade convertible debt securities.The fund may invest up to 20% of its total assets in securities of non-U.S. issuers, including up to 5% of its total assets in securities of emerging markets issuers.The fund may use derivatives for a variety of purposes, including: as a hedge against adverse changes in the market prices 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 hold cash or other short-term investments.

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Summary Prospectus The fund may lend securities in its portfolio to earn additional income. The fund may lend up to 33^⅓% of its total assets. Any income realized through securities lending may help fund performance.The fund uses a “growth at a reasonable price” style of management and seeks to invest in securities of issuers with above average potential for earnings and revenue growth that are also trading at attractive market valuations. To select stocks, the fund’s investment adviser employs fundamental research and an evaluation of the issuer based on its financial statements and operations, utilizing a bottom-up analytic style which focuses on specific securities rather than industries. The adviser may also use quantitative analysis. 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 issuer no longer offers the potential for growth at a reasonable price or if any of the factors used to select an investment have deteriorated. The adviser makes that determination based upon the same criteria it uses to select portfolio securities.Principal risks of investing in the fundYou 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 stock market may perform poorly relative to other investments (this risk may be greater in the short term). 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,

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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.Growth style risk. The fund’s investments may not have the growth potential originally expected. Growth 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-size companies risk. Compared to large companies, small-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.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 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.Risks of non-U.S. investments. Investing in non-U.S. issuers 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, currency risks, changes in economic, political, regulatory and social conditions, sustained economic downturns, tax burdens, and investment and repatriation restrictions. Non-U.S. issuers may be located in parts of the world that have historically been prone to natural disasters.

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Summary Prospectus 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. 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.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 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.Portfolio turnover risk. If the fund does a lot of trading, it may incur additional operating expenses, which would reduce performance, and could cause shareowners to incur a higher level of taxable income or capital gains.Securities lending risk. When lending securities in its portfolio, the fund will continue to have market risk and other risks associated with owning the securities on loan, as well as the risks associated with the investment of the cash collateral received in connection with the loan. Securities lending is also subject to the risk that the borrower fails to return a loaned security, and/or there is a shortfall on the collateral to be returned to the borrower, and the risk that the fund is unable to recall a security in time to exercise voting rights or sell the security.

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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 fund’s past performanceThe 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 Russell 2000 Growth 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 acquired the assets and liabilities of Safeco Growth Opportunities Fund (the predecessor fund) on December 10, 2004.The performance of Class A, Class B and Class C shares of the fund includes the net asset value performance of the predecessor fund’s Class A, Class B and Class C shares prior to the reorganization, which has been restated to reflect differences in any applicable sales charges (but not differences in expenses). If all the expenses of the Pioneer fund were reflected, the performance would be lower. Prior to August 2, 2004, Safeco Asset Management, Inc. served as the predecessor fund’s investment adviser.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.

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Summary Prospectus Annual return Class A shares (%)(Year ended December 31)

For the period covered by the bar chart:The highest calendar quarterly return was 34.38% (04/01/2001 to 06/30/2001)The lowest calendar quarterly return was –26.86% (07/01/2002 to 09/30/2002)Average annual total return (%)(for periods ended December 31, 2010)

	1 Year	5 Years	10 Years	Since Inception	Inception Date
Class A					9/30/96
Return before taxes	12.73	0.96	3.96	6.69
Return after taxes on distributions	12.73	0.26	3.60	6.06
Return after taxes on distributions and sale of shares	8.27	0.74	3.41	5.69
Class B	14.21	0.87	3.50	6.10	9/30/96
Class C	18.48	1.04	3.62	2.56	4/30/00
Class R	19.30	N/A	N/A	22.40	8/3/09
Class Y	20.26	2.72	N/A	3.02	9/23/05
Russell 2000 Growth Index (reflects no deduction for fees, expenses or taxes)	29.09	5.30	3.78	4.39	9/30/96

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

Investment adviser	Pioneer Investment Management, Inc.
Portfolio management	Mr. Brian E. Stack, senior vice president of Pioneer (portfolio manager of the fund since 2008).

Purchase and sale of fund sharesYou 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. There is no minimum investment amount for Class R 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 informationYou normally will have to pay income taxes on the dividends and capital gain distributions you receive from the fund, unless you are investing through a tax-deferred account, such as a 401(k) plan or individual retirement account.

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Summary Prospectus Payments to broker-dealers and other financial intermediariesIf 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.

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Notes


23449-00-0511