0001174520 2011-12-13 2012-12-12 0001174520 pstx5:S000004137Member 2011-12-13 2012-12-12 0001174520 pstx5:S000004137Member pstx5:C000011600Member 2011-12-13 2012-12-12 0001174520 pstx5:S000004137Member pstx5:C000011601Member 2011-12-13 2012-12-12 0001174520 pstx5:S000004137Member pstx5:C000011602Member 2011-12-13 2012-12-12 0001174520 pstx5:S000004137Member pstx5:C000121111Member 2011-12-13 2012-12-12 0001174520 pstx5:S000004137Member pstx5:C000115405Member 2011-12-13 2012-12-12 0001174520 pstx5:S000004137Member pstx5:C000075918Member 2011-12-13 2012-12-12 0001174520 pstx5:S000004137Member pstx5:C000115406Member 2011-12-13 2012-12-12 0001174520 pstx5:S000004137Member rr:AfterTaxesOnDistributionsMember pstx5:C000011600Member 2011-12-13 2012-12-12 0001174520 pstx5:S000004137Member rr:AfterTaxesOnDistributionsAndSalesMember pstx5:C000011600Member 2011-12-13 2012-12-12 0001174520 pstx5:S000004137Member pstx5:RussellThousandGrowthIndexMember 2011-12-13 2012-12-12 pure iso4217:USD Other 2012-03-31 PIONEER SERIES TRUST X 0001174520 false 2012-12-12 2012-12-12 2012-12-12 PIONEER FUNDAMENTAL GROWTH FUND<br/><br/>Fund summary 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.<br/><br/>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 &#8220;Sales charges&#8221; section of the prospectus beginning on page 31 and the &#8220;Sales charges&#8221; section of the statement of additional information beginning on page 51. SHAREOWNER FEES<br/>(fees paid directly from your investment) ANNUAL FUND OPERATING EXPENSES<br/> (expenses that you pay each year as a percentage of the value of your investment) EXAMPLE IF YOU DO NOT REDEEM YOUR SHARES<br/>NUMBER OF YEARS YOU OWN YOUR SHARES IF YOU REDEEM YOUR SHARES<br/>NUMBER OF YEARS YOU OWN YOUR SHARES PORTFOLIO TURNOVER The fund pays transaction costs, such as commissions, when it buys and sells securities (or &#8220;turns over&#8221; 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&#8217;s performance. During the most recent fiscal year, the fund&#8217;s portfolio turnover rate was 16% 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 equity securities of large companies, that is, companies similar in size to issuers included in the Russell 1000 Growth Index. The Russell 1000 Growth Index (the &#8220;index&#8221;) is a large capitalization index that measures the performance of those companies in the Russell 1000 Index with higher price-to-book ratios and higher forecasted growth values. On June 30, 2012, securities in the index had market capitalizations of approximately $1.3 billion or greater. The size of the companies in the index changes constantly as a result of market conditions and the composition of the index. The fund&#8217;s investments will not be confined to securities issued by companies included in the index.<br/><br/> For purposes of the fund&#8217;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, warrants, rights, equity interests in real estate investment trusts (REITs) and preferred stocks.<br/><br/> The fund primarily invests in securities of U.S. issuers. The fund may invest in securities of issuers in any industry or market sector. The fund may invest up to 20% of its total assets in equity and debt securities of non-U.S. issuers. The fund will not invest more than 10% of its total assets in the securities of emerging markets issuers.<br/><br/> The fund may also invest in investment grade and below investment grade debt securities (known as &#8220;junk bonds&#8221;), including below investment grade convertible debt securities and securities of issuers that are in default.<br/><br/> The fund may, but is not required to, use derivatives. The fund may use derivatives 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&#8217;s return as a non-hedging strategy that may be considered speculative. 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 also hold cash or other short-term investments.<br/><br/> The fund&#8217;s investment adviser uses a &#8220;growth&#8221; style of management and seeks to invest in securities of issuers with above average potential for earnings and revenue growth. To select growth stocks, the adviser employs quantitative analysis, fundamental research, and an evaluation of the issuer based on its financial statements and operations, utilizing a bottom-up analytic style. The adviser relies on the knowledge, experience and judgment of its staff and the staff of its affiliates who have access to a wide variety of research. The adviser focuses on the quality and price of individual issuers, not on economic sector or market-timing strategies.<br/><br/> The adviser generally sells a portfolio security when it believes that the issuer no longer offers the potential for above average earnings and revenue growth. 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.<br/><br/> 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 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 financial crisis that began in 2008 has caused a significant decline in the value and liquidity of many securities of issuers worldwide. Some governmental and non-governmental issuers (notably in Europe) 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. The 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 the value and liquidity of certain securities. 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&#8217;s investments may be negatively affected by the countries experiencing these difficulties. In addition, legislation recently enacted in the U.S. is changing many aspects of financial regulation. The impact of the legislation 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.<br/><br/> GROWTH STYLE RISK. The fund&#8217;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.<br/><br/> PORTFOLIO SELECTION RISK. The adviser&#8217;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.<br/><br/> RISKS OF NON-U.S. INVESTMENTS. Investing in non-U.S. issuers or issuers with 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&#8217;s return. Non-U.S. issuers may be located in parts of the world that have historically been prone to natural disasters.<br/><br/> 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.<br/><br/> 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.<br/><br/> DERIVATIVES RISK. Using 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&#8217;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&#8217;s initial investment. Changes in a derivative&#8217;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 fully known and may not be 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.<br/><br/> 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&#8217;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.<br/><br/> EXPENSE RISK. Your actual costs of investing in the fund may be higher than the expenses shown in &#8220;Annual fund operating expenses&#8221; 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.<br/><br/> Please note that there are many other factors that could adversely affect your investment and that could prevent the fund from achieving its goals.<br/><br/>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&#8217;S PAST PERFORMANCE ANNUAL RETURN CLASS A SHARES (%)<br/>(Year ended December 31) 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&#8217;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 1000 Growth Index, a broad-based measure of market performance that has characteristics relevant to the fund&#8217;s investment strategies. You can obtain updated performance information by visiting https://us.pioneerinvestments.com/performance or by calling 1-800-225-6292.<br/><br/>The fund&#8217;s past performance (before and after taxes) does not necessarily indicate how it will perform in the future.<br/><br/>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. For the period covered by the bar chart:<br/> THE HIGHEST CALENDAR QUARTERLY RETURN WAS 14.05% (10/01/2004 TO 12/31/2004).<br/> THE LOWEST CALENDAR QUARTERLY RETURN WAS -19.50% (10/01/2008 TO 12/31/2008).<br/><br/>At September 30, 2012, the year-to-date return was 17.00%. No performance information is presented for Class K, Class R or Class Z shares in the table because Class K, Class R or Class Z shares do not have annual returns for at least one calendar year. The returns for Class K, Class R and Class Z shares would differ from those of Class A, Class B, Class C and Class Y shares because they have different expenses. AVERAGE ANNUAL TOTAL RETURN (%)<br/>(for periods ended December 31, 2011) 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&#8217;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.<br/><br/> After-tax returns are shown only for Class A shares. After-tax returns for Class B, Class C, Class K, Class R, Class Y and Class Z shares shares will vary. August 1, 2014 0.16 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. 50000 Other expenses for Class K, Class R and Class Z shares are based on estimated amounts for the current fiscal year. You could lose money on your investment in the fund. An investment in the fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other 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 Russell 1000 Growth Index, a broad-based measure of market performance that has characteristics relevant to the fund's investment strategies. 1-800-225-6292 https://us.pioneerinvestments.com/performance The fund&#8217;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. 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. 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 K, Class R, Class Y and Class Z shares shares will vary. 0.0575 0 0 0 0 0 0 0 0 0 0 0 0.04 0.01 0.0065 0.0065 0.0065 0.0065 0.0065 0.0065 0.0065 0.0025 0.01 0.01 0 0.005 0 0 0.0029 0.0064 0.0031 0.0006 0.0035 0.0013 0.003 0.0119 0.0229 0.0196 0.0071 0.015 0.0078 0.0095 -0.001 -0.0014 0 -0.0005 0 -0.001 0 0.0109 0.0215 0.0196 0.0071 0.014 0.0078 0.009 680 618 299 73 143 80 92 922 1002 615 227 464 249 298 1183 1312 1057 395 809 433 521 1927 2338 883 2285 1782 966 1162 680 218 199 73 143 80 92 922 702 615 227 464 249 298 1212 1057 395 1183 809 433 521 1927 2338 2285 883 1782 966 1162 0.3215 0.0848 0.0435 0.0873 0.0978 -0.3106 0.3398 0.1053 0.0632 THE HIGHEST CALENDAR QUARTERLY RETURN 2004-12-31 0.1405 THE LOWEST CALENDAR QUARTERLY RETURN 2008-12-31 -0.195 year-to-date return 2012-09-30 0.17 0.002 -0.0029 0.0062 0.0133 0.0539 0.067 0.0264 0.0235 0.0189 0.0191 0.0263 0.0274 0.025 0.0544 0.0462 0.0447 0.0311 0.032 0.1795 0.053 2002-08-22 2002-08-22 2002-08-22 2005-12-15 2005-12-15 2009-04-08 2002-08-22 <div style="display:none">~ http://www.pioneerinvestments.com/role/ScheduleShareholderFeesPioneerFundamentalGrowthFund column period compact * ~</div> <div style="display:none">~ http://www.pioneerinvestments.com/role/ScheduleAnnualFundOperatingExpensesPioneerFundamentalGrowthFund column period compact * ~</div> <div style="display:none">~ http://www.pioneerinvestments.com/role/ScheduleExpenseExampleTransposedPioneerFundamentalGrowthFund column period compact * ~</div> <div style="display:none">~ http://www.pioneerinvestments.com/role/ScheduleExpenseExampleNoRedemptionTransposedPioneerFundamentalGrowthFund column period compact * ~</div> <div style="display:none">~ http://www.pioneerinvestments.com/role/ScheduleAnnualTotalReturnsPioneerFundamentalGrowthFundBarChart column period compact * ~</div> <div style="display:none">~ http://www.pioneerinvestments.com/role/ScheduleAverageAnnualTotalReturnsTransposedPioneerFundamentalGrowthFund column period compact * ~</div> 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: Other expenses for Class K, Class R and Class Z shares are based on estimated amounts for the current fiscal year. 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 and brokerage commissions) to the extent required to reduce fund expenses to 1.09%, 2.15%, 1.40% and 0.90% of the average daily net assets attributable to Class A, Class B, Class R and Class Z shares, respectively. These expense limitations are in effect through August 1, 2014. There can be no assurance that the adviser will extend the expense limitations beyond such time. While in effect, the arrangement may be terminated for a class only by agreement of the adviser and the Board of Trustees.