UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM N-CSR CERTIFIED SHAREHOLDER REPORT OF REGISTERED MANAGEMENT INVESTMENT COMPANIES 		Investment Company Act file number 811-01835 Pioneer Series Trust XI (Exact name of registrant as specified in charter) 60 State Street, Boston, MA 02109 (Address of principal executive offices) (ZIP code) Terrence J. Cullen, Pioneer Investment Management, Inc., 60 State Street, Boston, MA 02109 (Name and address of agent for service) Registrant's telephone number, including area code: (617) 742-7825 Date of fiscal year end: December 31 Date of reporting period: January 1, 2017 through JUne 30, 2017 Form N-CSR is to be used by management investment companies to file reports with the Commission not later than 10 days after the transmission to stockholders of any report that is required to be transmitted to stockholders under Rule 30e-1 under the Investment Company Act of 1940 (17 CFR 270.30e-1). The Commission may use the information provided on Form N-CSR in its regulatory, disclosure review, inspection, and policymaking roles. A registrant is required to disclose the information specified by Form N-CSR, and the Commission will make this information public. A registrant is not required to respond to the collection of information contained in Form N-CSR unless the Form displays a currently valid Office of Management and Budget ("OMB") control number. Please direct comments concerning the accuracy of the information collection burden estimate and any suggestions for reducing the burden to Secretary, Securities and Exchange Commission, 450 Fifth Street, NW, Washington, DC 20549-0609. The OMB has reviewed this collection of information under the clearance requirements of 44 U.S.C. ss. 3507. ITEM 1. REPORTS TO STOCKHOLDERS. Pioneer Core Equity Fund -------------------------------------------------------------------------------- Semiannual Report | June 30, 2017 -------------------------------------------------------------------------------- Ticker Symbols: Class A PIOTX Class C PCOTX Class Y PVFYX [LOGO] Amundi Pioneer ============== ASSET MANAGEMENT visit us: amundipioneer.com Table of Contents President's Letter 2 Portfolio Management Discussion 4 Portfolio Summary 10 Prices and Distributions 11 Performance Update 12 Comparing Ongoing Fund Expenses 15 Schedule of Investments 17 Financial Statements 22 Notes to Financial Statements 29 Additional Information 38 Approval of New and Interim Management Agreements 40 Trustees, Officers and Service Providers 48 Pioneer Core Equity Fund | Semiannual Report | 6/30/17 1 President's Letter U.S. markets have continued to generate positive returns during the first several months of 2017, with so-called "risk" assets, such as equities and credit-sensitive bonds, posting solid gains. U.S. equities, as measured by the Standard & Poor's 500 Index, returned slightly more than 6% in the first calendar quarter of the year and more than 3% for the second quarter. Meanwhile, high-yield securities have dominated bond market performance thus far in 2017. The post-election market momentum we witnessed in the U.S. during the final weeks of the fourth quarter of 2016 slowed only when oil prices slumped in March, due to both higher-than-expected inventories and concerns over whether OPEC (Organization of Petroleum Exporting Countries) would continue its supply cuts. Not even the Federal Reserve System's (the Fed's) two rate hikes since March, nor Britain's trigger of Article 50 to begin the "Brexit" process caused any dramatic sell-off of risk assets. In fact, we are encouraged by the more hawkish stance of the Fed with regard to interest rates, in light of our view that current U.S. bond yields do not fairly reflect the prospective levels of economic activity and inflation. We expect the Fed to continue to tighten monetary policy, with at least one more rate hike likely to occur before the end of 2017. While U.S. gross domestic product (GDP) did slow in the first quarter, ending up at 1.4% after revisions, the expectation is for GDP growth to pick-up in the second quarter, with a solid consumer leading the way. It is our view that the U.S. economy may lead all developed nations in 2017, with GDP growth in excess of 2% for the full year, even if proposed tax and regulatory reforms are not passed into law in the near future. We also believe solid domestic employment figures should continue to support consumption and the housing market, and that stronger corporate profits and increased government spending may contribute to economic growth in 2018 and beyond. In addition, as we monitor global Purchasing Manager Indices (PMIs), we note that their numbers are increasing, which suggests that growth in global economies is also improving. (PMIs are used to measure the economic health of the manufacturing sector.) There are, as always, some risks to our outlook. First, the market already has priced in a good deal of the Trump economic reform platform, and that could lead to near-term disappointment if Congressional follow-through does not happen this year. The future of the Affordable Care Act (ACA) is another potential concern, as Congressional leaders have, thus far, failed to generate 2 Pioneer Core Equity Fund | Semiannual Report | 6/30/17 enough support to get new health care legislation approved by both houses. However, if a bill is eventually passed that either eliminates or significantly alters the ACA, the new law will undoubtedly have an effect on the health care sector, one of the largest segments of the U.S. economy. Geopolitical risks, of course, remain a potential headwind, given ongoing strife in the Middle East and renewed tensions on the Korean Peninsula. While our current outlook is generally optimistic, conditions can and often do change, and while passive investment strategies may have a place in one's overall portfolio, it is our view that all investment decisions are active choices. Throughout our history, we have believed in the importance of active management. The active decisions to invest in equities or fixed-income securities are made by a team of experienced investment professionals focusing on identifying value across global markets using proprietary research, careful risk management, and a long-term perspective. We believe our shareowners can benefit from the experience and tenure of our investment teams as well as the insights generated from our extensive research process. As always, and particularly during times of market uncertainty, we encourage you to work with your financial advisor to develop an overall investment plan that addresses both your short- and long-term goals, and to implement such a plan in a disciplined manner. We greatly appreciate the trust you have placed in us and look forward to continuing to serve you in the future. Sincerely, /s/ Lisa M. Jones Lisa M. Jones Head of the Americas, President and CEO of US Amundi Pioneer Asset Management USA, Inc. June 30, 2017 Any information in this shareowner report regarding market or economic trends or the factors influencing the Fund's historical or future performance are statements of opinion as of the date of this report. Past performance is no guarantee of future results. Pioneer Core Equity Fund | Semiannual Report | 6/30/17 3 Portfolio Management Discussion | 6/30/17 Important Note: On July 3, 2017, Amundi acquired Pioneer Investments, a group of asset management companies located throughout the world. Amundi, one of the world's largest asset managers, is headquartered in Paris, France. As a result of the transaction, Pioneer Investment Management, Inc., the Fund's investment adviser, became an indirect wholly owned subsidiary of Amundi and Amundi's wholly owned subsidiary, Amundi USA, Inc. Prior to July 3, 2017, Pioneer Investments was owned by Pioneer Global Asset Management S.p.A., a wholly owned subsidiary of UniCredit S.p.A. In connection with the transaction, the names of the Fund's investment adviser and principal underwriter changed. Effective July 3, 2017, the name of Pioneer Investment Management, Inc. changed to Amundi Pioneer Asset Management, Inc. and the name of Pioneer Funds Distributor, Inc. changed to Amundi Pioneer Distributor, Inc. This transaction does not impact your existing relationship with Pioneer Investments, your advisor, or the methods you use to communicate with us, as the investor contact telephone numbers and services you expect will remain the same. We are excited, however, to be launching a new website representing the combined company. Come visit us at: www.amundipioneer.com Domestic stocks generated solid performance over the first half of 2017. In the following interview, Craig D. Sterling discusses the market environment and the factors that influenced the performance of Pioneer Core Equity Fund during the six-month period ended June 30, 2017. Mr. Sterling, Head of Equity Research, U.S., a senior vice president, and a portfolio manager at Amundi Pioneer Asset Management, Inc. ("Amundi Pioneer"), is responsible for day-to-day management of the Fund's investment portfolio, along with John Peckham, a senior vice president and a portfolio manager at Amundi Pioneer. Q How did the Fund perform during the six-month period ended June 30, 2017? A Pioneer Core Equity Fund's Class A shares returned 10.94% at net asset value during the six-month period ended June 30, 2017, while the Fund's benchmark, the Standard & Poor's 500 Index (the S&P 500), returned 9.33%. During the same period, the average return of the 869 mutual funds in Lipper's Large-Cap Core Funds category was 8.72%, and the average return of the 1,459 mutual funds in Morningstar's Large Blend Funds category was 8.65%. Q How would you describe the investment environment for equities during the six-month period ended June 30, 2017? A The equity market moved higher overall and produced healthy returns during the period, although at the start of the year, we saw the cyclical rally that began before the November 2016 elections start to fade. That rally once again picked-up velocity after the victories of Donald J. Trump and the 4 Pioneer Core Equity Fund | Semiannual Report | 6/30/17 Congressional Republicans in the November elections. We believe cyclical stocks moved too far, too fast, however, as equity valuations in early 2017 implied meaningful corporate profit increases while anticipating certain levels of accelerating economic growth. In addition, the stock market surge assumed that President Trump and the Republican-controlled Congress could reach accords on certain key legislative measures, with health care reform (the repeal or replacement of the Affordable Care Act) as well as pro-growth fiscal policies such as corporate and income tax cuts and regulatory reform near the top of the agenda. Some of the biggest sectors and market segments that were post-election winners, like energy, banks, and cyclical industrial stocks, soon began to lag as economic and legislative realities as well as moderating equity valuations set in. For banks, that materialized into a flatter yield curve and slower loan growth, while for energy producers, lower oil prices, with corporate profits directly affected in each case. On the other side of the valuation spectrum, at the start of the period in early 2017, the share prices of companies considered secular winners within the information technology and consumer sectors (commonly referred to as "FAANG" stocks -- Facebook, Apple, Amazon.com, Netflix, and Google) did not fully reflect the powerful profit growth, high returns on capital, and competitive advantages of those firms, and they ended up leading the market over the full six months. Additionally, the fits and starts characterizing the Affordable Care Act repeal-and-replace effort by the Republicans had a positive effect on stock prices within the health care sector, which rebounded with an 18% return during the six-month period, the second-best sector performance after information technology. The traditionally stable, high-dividend paying* sectors - consumer staples and utilities - performed well during the period as the "Trump trade" unwound, but gave up most of their outperformance in late May and into June as healthy global economic growth became obvious and central banks increasingly signaled a commitment to tapering their post-financial-crisis monetary stimulus. Combined with historically expensive equity valuations, those factors made potentially higher-yielding stocks less attractive. Moreover, the announcement of Amazon's acquisition of retail grocer Whole Foods stimulated market conjecture about what changes might emerge if Amazon were to become an even larger presence in the retail sales and distribution area, thus creating a potentially new secular threat to consumer staples companies. Telecom services was also a poor-performing sector during the period, significantly lagging the S&P 500, as the competitive dynamics of the wireless industry has become increasingly value-destructive. * Dividends are not guaranteed. Pioneer Core Equity Fund | Semiannual Report | 6/30/17 5 Q What were the principal factors driving the Fund's outperformance of the S&P 500 Index during the six-month period ended June 30, 2017? A Our decision to deeply underweight the portfolio in energy stocks, which we thought had reached unattractively high valuations in 2016, was the biggest single factor driving the Fund's outperformance of its benchmark during the period. Early in the 2017 calendar year, the Fund had almost no energy exposure, as we believed then-current stock valuations were too dependent on expectations of very high future oil prices. The underweighted position turned into a big advantage for the Fund when energy stocks underperformed over the six months. Late in the period, we did add ExxonMobil back into the portfolio, as it is probably the most conservative stock in the energy sector. Nevertheless, we continue to be cautious with regard to adding too much exposure to energy companies. Excellent stock selection results in the industrials sector also contributed significantly to the Fund's benchmark-relative returns, led by strong performance from holdings such as CSX and Masco. CSX is an under- earning railroad operator that attracted an activist investor, which in turn led to the appointment of a new CEO who is a noted turnaround expert in the railroad industry. Masco is a manufacturer of architectural coatings and household fixtures, with brands that include Behr Paints and Delta Faucets. In addition, our decision to avoid owning shares of General Electric aided the Fund's benchmark-relative performance, as the stock underperformed due to continued disappointing financial results and business-model execution. An overweight to and positive security selection results within information technology also contributed positively to the Fund's benchmark-relative results during the period, with Apple once again turning in excellent performance as the market continues to anticipate its next-generation iPhone and as the company's services business continues to grow at a rapid pace. The Fund also had significant positions in banking institutions, which we favored because of their improving prospects in a rising-interest-rate environment and the likelihood of some regulatory relief coming from the Federal government under the new administration. JPMorgan Chase and PNC Financial Services were two of the most notable contributors to the Fund's performance among the portfolio's banking holdings. Among other individual positions, a large contributor to the Fund's benchmark-relative results was Cooper Companies, one of the world's largest manufacturers of daily-wear contact lenses. The stock rallied during the period as the competitive landscape continued to favor a few dominant companies, including Cooper. 6 Pioneer Core Equity Fund | Semiannual Report | 6/30/17 Q What investment decisions or individual holdings detracted from the Fund's benchmark-relative performance during the six-month period ended June 30, 2017? A The biggest factor holding back benchmark-relative performance during the period was the Fund's positioning in the consumer discretionary sector, especially in auto parts retailers such as O'Reilly Automotive and Advance Auto Parts, both of which operate national store chains. The two stocks underperformed as each company experienced unanticipated negative effects from relatively mild winter weather and delayed tax refunds. The companies also faced the perception of increased competitive challenges from e-commerce players, led by Amazon. We retained the Fund's position in O'Reilly Automotive, but sold Advance Auto Parts from the portfolio. One of the other big detractors from the Fund's benchmark-relative results during the period was Synchrony Financial, which had been a positive contributor to the Fund's performance in 2016. Synchrony, which is the nation's largest provider of private-label credit cards, including store- branded cards, underperformed after announcing it was setting aside higher reserves for credit losses. We liquidated the Fund's position before the end of the period. However, we have retained a portfolio position in another underperformer, Sealed Air, which produces specialized packaging materials for a variety of industries. Sealed Air disappointed investors during the period when it made a sloppy divestiture of an underperforming business unit. Nevertheless, we like the prospects for the company's remaining business units. Despite the recent setback, we believe Sealed Air remains a stable leader and innovator in its two remaining business segments -- protein (food) and product-care packaging. Q Did the Fund have any investments in derivative securities during the six- month period ended June 30, 2017? A No, the Fund held no investments in any derivatives during the period. Q What is your investment outlook and how have you positioned the Fund's portfolio heading into the second half of 2017? A We remain optimistic about stocks, as we think valuations should continue to be supported by improving corporate profits, which tend to reduce pressure on the market's equity risk premium and valuation multiples. Domestic equities, in our opinion, are reasonably priced, especially relative to the prices of alternative asset classes, and we do not believe they face any imminent threats of a recession, excessive inflation, or rapidly rising interest rates. Nonetheless, the inflation outlook, the potential for increased levels of global conflict, and political dysfunction in Washington continue to be factors that warrant focus with regard to both the Fund's positioning and our overall views. Pioneer Core Equity Fund | Semiannual Report | 6/30/17 7 We believe stock prices of some companies that, in general, do not face direct, massive threats from Amazon, have been overly beaten down by investors who underestimated the durability of those companies' business models. Specifically, those would be: 1) retailers that have unique relationships with professionals (for example, auto repair shops, professional painters, and contractors), in which time-to-delivery can be more important than price, and where complex supply chains are already built out; 2) off-price retailers such as TJX and eBay, which have extensive business models that are difficult to replicate; or 3) dollar stores that cater to low-income consumers, as it is not clear that even Amazon can profitably cater to customers whose average shopping trips total $15 or less. Nearly 10% of the Fund's total investment portfolio is allocated to that theme. We like the long-term housing/repair and remodel theme and trend, which we believe has a runway for an extended cycle. Birthrates among women more than 25 years old have accelerated, and children have always been a catalyst for single-family living. Home affordability relative to income remains attractive and credit availability is improving. Home-price inflation, too, is healthy and a major driver of home improvement spending. We have allocated approximately seven percent of the Fund's total investment portfolio towards that theme, through positions in Home Depot, Sherwin-Williams, and Masco. In health care, we believe that managed care is part of any solution to the industry's lingering issues in the U.S., and we consider Medicare and Medicaid providers to be secular winners. As a result, over three percent of the Fund's total investment portfolio is allocated to that segment of the health care sector. Moreover, we continue to find value in pharmaceutical and biotechnology firms, as we think the market is overly discounting drug-development pipelines and undervaluing the sustainability of profits from existing drugs. We also continue to find opportunities in banks, as valuations within the group remain compelling. We believe that interest rates will head higher as inflation picks up and global economic growth increases, and the pendulum appears to have shifted towards fewer regulations affecting near-term profitability. Moreover, we believe the improvement to banks' profitability from fewer branches and emerging "fintech" developments is not well understood by the market. (Fintech represents computer programs and other technology used to support or enable banking and financial services). Finally, while we saw value in 2016 in many capital goods and equipment companies, we see less value in 2017 and have cut back the portfolio's exposure, moving to an underweight position. 8 Pioneer Core Equity Fund | Semiannual Report | 6/30/17 In selecting securities for the portfolio, we continue to rely on the combination of our experienced team of fundamental analysts and a proprietary corporate performance and valuation framework grounded in business-model economics. We believe those two key components of our investment process are critical to the success of the Fund, given the ever- evolving secular shifts taking place in nearly every industry. Please refer to the Schedule of Investments on pages 17-21 for a full listing of Fund securities. All investments are subject to risk, including the possible loss of principal. In the past several years, financial markets have experienced increased volatility, depressed valuations, decreased liquidity and heightened uncertainty. These conditions may continue, recur, worsen or spread. At times, the Fund's investments may represent industries or industry sectors that are interrelated or have common risks, making it more susceptible to any economic, political, or regulatory developments or other risks affecting those industries and sectors. Investing in foreign and/or emerging markets securities involves risks relating to interest rates, currency exchange rates, economic, and political conditions. These risks may increase share price volatility. Before investing, consider the product's investment objectives, risks, charges and expenses. Contact your advisor or Amundi Pioneer Asset Management, Inc., for a prospectus or summary prospectus containing this information. Read it carefully. Any information in this shareholder report regarding market or economic trends or the factors influencing the Fund's historical or future performance are statements of opinion as of the date of this report. Past performance is no guarantee of future results. Pioneer Core Equity Fund | Semiannual Report | 6/30/17 9 Portfolio Summary | 6/30/17 Portfolio Diversification -------------------------------------------------------------------------------- (As a percentage of total investment portfolio) [THE FOLLOWING DATA WAS REPRESENTED AS A PIE CHART IN THE PRINTED MATERIAL] U.S. Common Stocks 95.4% International Common Stocks 3.0% Depository Receipts for International Stocks 1.1% U.S. Government Securities 0.5% Sector Distribution -------------------------------------------------------------------------------- (As a percentage of equity holdings) [THE FOLLOWING DATA WAS REPRESENTED AS A PIE CHART IN THE PRINTED MATERIAL] Information Technology 23.6% Consumer Discretionary 16.7% Financials 15.1% Health Care 13.5% Industrials 9.6% Energy 6.5% Consumer Staples 5.4% Materials 4.8% Utilities 3.2% Telecommunication Services 1.6% 10 Largest Holdings -------------------------------------------------------------------------------- (As a percentage of equity holdings)* 1. Apple, Inc. 4.69% -------------------------------------------------------------------------------- 2. Exxon Mobil Corp. 4.64 -------------------------------------------------------------------------------- 3. Microsoft Corp. 3.61 -------------------------------------------------------------------------------- 4. JPMorgan Chase & Co. 3.47 -------------------------------------------------------------------------------- 5. Comcast Corp. 3.39 -------------------------------------------------------------------------------- 6. Citigroup, Inc. 3.35 -------------------------------------------------------------------------------- 7. American Electric Power Co, Inc. 3.25 -------------------------------------------------------------------------------- 8. Alphabet, Inc. 3.18 -------------------------------------------------------------------------------- 9. Visa, Inc. 2.97 -------------------------------------------------------------------------------- 10. The Home Depot, Inc. 2.94 -------------------------------------------------------------------------------- * This list excludes temporary cash investments. The Fund is actively managed, and current holdings may be different. The holdings listed should not be considered recommendations to buy or sell any securities listed. 10 Pioneer Core Equity Fund | Semiannual Report | 6/30/17 Prices and Distributions | 6/30/17 Net Asset Value per Share -------------------------------------------------------------------------------- -------------------------------------------------------------------------------- Class 6/30/17 12/31/16 -------------------------------------------------------------------------------- A $ 19.98 $ 18.01 -------------------------------------------------------------------------------- C $ 17.86 $ 16.17 -------------------------------------------------------------------------------- Y $ 20.19 $ 18.18 -------------------------------------------------------------------------------- Distributions per Share: 1/1/17 - 6/30/17 -------------------------------------------------------------------------------- -------------------------------------------------------------------------------- Net Investment Short-Term Long-Term Class Income Capital Gains Capital Gains -------------------------------------------------------------------------------- A $ -- $ -- $ -- -------------------------------------------------------------------------------- C $ -- $ -- $ -- -------------------------------------------------------------------------------- Y $ -- $ -- $ -- -------------------------------------------------------------------------------- Index Definition -------------------------------------------------------------------------------- The Standard & Poor's 500 Index is an unmanaged, commonly used measure of the broad U.S. stock market. Index returns are calculated monthly, assume reinvestment of dividends and, unlike Fund returns, do not reflect any fees, expenses or sales charges. It is not possible to invest directly in an index. The index defined here pertains to the "Value of $10,000 Investment" and "Value of $5 Million Investment" charts on pages 12-14. Pioneer Core Equity Fund | Semiannual Report | 6/30/17 11 Performance Update | 6/30/17 Class A Shares Investment Returns -------------------------------------------------------------------------------- The mountain chart on the right shows the change in value of a $10,000 investment made in Class A shares of Pioneer Core Equity Fund at public offering price during the periods shown, compared to that of the Standard & Poor's 500 Index. Average Annual Total Returns (As of June 30, 2017) -------------------------------------------------------------------------------- Net Public Asset Offering S&P Value Price 500 Period (NAV) (POP) Index -------------------------------------------------------------------------------- 10 years 6.49% 5.86% 7.18% 5 years 12.47 11.14 14.62 1 year 21.12 14.14 17.88 -------------------------------------------------------------------------------- Expense Ratio (Per prospectus dated May 1, 2017) -------------------------------------------------------------------------------- Gross -------------------------------------------------------------------------------- 0.94% -------------------------------------------------------------------------------- [THE FOLLOWING DATA WAS REPRESENTED AS A MOUNTAIN CHART IN THE PRINTED MATERIAL] Value of $10,000 Investment Pioneer Core S&P 500 Index Equity Fund 6/07 $ 9,425 $10,000 6/08 $ 8,295 $ 8,689 6/09 $ 6,293 $ 6,413 6/10 $ 7,097 $ 7,338 6/11 $ 9,439 $ 9,589 6/12 $ 9,824 $10,109 6/13 $11,528 $12,190 6/14 $14,269 $15,187 6/15 $15,001 $16,313 6/16 $14,596 $16,963 6/17 $17,678 $19,996 Call 1-800-225-6292 or visit www.amundipioneer.com for the most recent month-end performance results. Current performance may be lower or higher than the performance data quoted. The performance data quoted represents past performance, which is no guarantee of future results. Investment return and principal value will fluctuate, and shares, when redeemed, may be worth more or less than their original cost. NAV results represent the percent change in net asset value per share. Returns would have been lower had sales charges been reflected. POP returns reflect deduction of maximum 5.75% sales charge. All results are historical and assume the reinvestment of dividends and capital gains. Other share classes are available for which performance and expenses will differ. Performance results reflect any applicable expense waivers in effect during the periods shown. Without such waivers Fund performance would be lower. Waivers may not be in effect for all funds. Certain fee waivers are contractual through a specified period. Otherwise, fee waivers can be rescinded at any time. See the prospectus and financial statements for more information. The performance table and graph do not reflect the deduction of fees and taxes that a shareowner would pay on Fund distributions or the redemption of Fund shares. The Fund acquired the assets and liabilities of Pioneer Research Fund ("the predecessor fund") on June 7, 2013. As a result of the reorganization, the predecessor fund's performance and financial history became the performance and financial history of the Fund. The performance of Class A shares of the Fund is the performance of Class A shares of the predecessor fund for periods prior to the reorganization, and has not been restated to reflect any differences in expenses. Please refer to the financial highlights for a more current expense ratio. 12 Pioneer Core Equity Fund | Semiannual Report | 6/30/17 Performance Update | 6/30/17 Class C Shares Investment Returns -------------------------------------------------------------------------------- The mountain chart on the right shows the change in value of a $10,000 investment made in Class C shares of Pioneer Core Equity Fund for the periods shown, compared to that of the Standard & Poor's 500 Index. Average Annual Total Returns (As of June 30, 2017) -------------------------------------------------------------------------------- S&P If If 500 Period Held Redeemed Index -------------------------------------------------------------------------------- 10 years 5.56% 5.56% 7.18% 5 years 11.49 11.49 14.62 1 year 20.09 20.09 17.88 -------------------------------------------------------------------------------- Expense Ratio (Per prospectus dated May 1, 2017) -------------------------------------------------------------------------------- Gross -------------------------------------------------------------------------------- 1.76% -------------------------------------------------------------------------------- [THE FOLLOWING DATA WAS REPRESENTED AS A MOUNTAIN CHART IN THE PRINTED MATERIAL] Value of $10,000 Investment Pioneer Core S&P 500 Index Equity Fund 6/07 $10,000 $10,000 6/08 $ 8,740 $ 8,689 6/09 $ 6,569 $ 6,413 6/10 $ 7,339 $ 7,338 6/11 $ 9,667 $ 9,589 6/12 $ 9,973 $10,109 6/13 $11,585 $12,190 6/14 $14,215 $15,187 6/15 $14,816 $16,313 6/16 $14,307 $16,963 6/17 $17,182 $19,996 Call 1-800-225-6292 or visit www.amundipioneer.com for the most recent month-end performance results. Current performance may be lower or higher than the performance data quoted. The performance data quoted represents past performance, which is no guarantee of future results. Investment return and principal value will fluctuate, and shares, when redeemed, may be worth more or less than their original cost. Class C shares held for less than one year are also subject to a 1% contingent deferred sales charge (CDSC). If you paid a 1% sales charge, your returns would be lower than those shown above. "If Held" results represent the percent change in net asset value per share. Returns would have been lower had sales charges been reflected. All results are historical and assume the reinvestment of dividends and capital gains. Other share classes are available for which performance and expenses will differ. Performance results reflect any applicable expense waivers in effect during the periods shown. Without such waivers Fund performance would be lower. Waivers may not be in effect for all funds. Certain fee waivers are contractual through a specified period. Otherwise, fee waivers can be rescinded at any time. See the prospectus and financial statements for more information. The performance table and graph do not reflect the deduction of fees and taxes that a shareowner would pay on Fund distributions or the redemption of Fund shares. The Fund acquired the assets and liabilities of Pioneer Research Fund ("the predecessor fund") on June 7, 2013. As a result of the reorganization, the predecessor fund's performance and financial history became the performance and financial history of the Fund. The performance of Class C shares of the Fund is the performance of Class C shares of the predecessor fund for periods prior to the reorganization, and has not been restated to reflect any differences in expenses. Please refer to the financial highlights for a more current expense ratio. Pioneer Core Equity Fund | Semiannual Report | 6/30/17 13 Performance Update | 6/30/17 Class Y Shares Investment Returns -------------------------------------------------------------------------------- The mountain chart on the right shows the change in value of a $5 million investment made in Class Y shares of Pioneer Core Equity Fund during the periods shown, compared to that of the Standard & Poor's 500 Index. Average Annual Total Returns (As of June 30, 2017) -------------------------------------------------------------------------------- Net Asset S&P Value 500 Period (NAV) Index -------------------------------------------------------------------------------- 10 years 6.81% 7.18% 5 years 12.80 14.62 1 year 21.40 17.88 -------------------------------------------------------------------------------- Expense Ratio (Per prospectus dated May 1, 2017) -------------------------------------------------------------------------------- Gross -------------------------------------------------------------------------------- 0.63% -------------------------------------------------------------------------------- [THE FOLLOWING DATA WAS REPRESENTED AS A MOUNTAIN CHART IN THE PRINTED MATERIAL] Value of $5 Million Investment Pioneer Core S&P 500 Index Equity Fund 6/07 $5,000,000 $5,000,000 6/08 $4,419,093 $4,344,346 6/09 $3,367,781 $3,206,268 6/10 $3,806,288 $3,668,890 6/11 $5,073,608 $4,794,496 6/12 $5,290,960 $5,054,739 6/13 $6,224,310 $6,095,190 6/14 $7,729,171 $7,593,575 6/15 $8,151,232 $8,156,631 6/16 $7,959,099 $8,481,654 6/17 $9,662,377 $9,998,237 Call 1-800-225-6292 or visit www.amundipioneer.com for the most recent month-end performance results. Current performance may be lower or higher than the performance data quoted. The performance data quoted represents past performance, which is no guarantee of future results. Investment return and principal value will fluctuate, and shares, when redeemed, may be worth more or less than their original cost. The Fund acquired the assets and liabilities of Pioneer Research Fund ("the predecessor fund") on June 7, 2013. As a result of the reorganization, the predecessor fund's performance and financial history became the performance and financial history of the Fund. The performance of Class Y shares of the Fund is the performance of Class Y shares of the predecessor fund for periods prior to the reorganization, and has not been restated to reflect any differences in expenses. Class Y shares are not subject to sales charges and are available for limited groups of eligible investors, including institutional investors. All results are historical and assume the reinvestment of dividends and capital gains. Other share classes are available for which performance and expenses will differ. Performance results reflect any applicable expense waivers in effect during the periods shown. Without such waivers Fund performance would be lower. Waivers may not be in effect for all funds. Certain fee waivers are contractual through a specified period. Otherwise, fee waivers can be rescinded at any time. See the prospectus and financial statements for more information. The performance table and graph do not reflect the deduction of fees and taxes that a shareowner would pay on Fund distributions or the redemption of Fund shares. Please refer to the financial highlights for a more current expense ratio. 14 Pioneer Core Equity Fund | Semiannual Report | 6/30/17 Comparing Ongoing Fund Expenses As a shareowner in the Fund, you incur two types of costs: (1) ongoing costs, including management fees, distribution and/or service (12b-1) fees, and other Fund expenses; and (2) transaction costs, including sales charges (loads) on purchase payments. This example is intended to help you understand your ongoing expenses (in dollars) of investing in the Fund and to compare these costs with the ongoing costs of investing in other mutual funds. The example is based on an investment of $1,000 at the beginning of the Fund's latest six-month period and held throughout the six months. Using the Tables -------------------------------------------------------------------------------- Actual Expenses The first table below provides information about actual account values and actual expenses. You may use the information in this table, together with the amount you invested, to estimate the expenses that you paid over the period as follows: (1) Divide your account value by $1,000 Example: an $8,600 account value (divided by) $1,000 = 8.6 (2) Multiply the result in (1) above by the corresponding share class's number in the third row under the heading entitled "Expenses Paid During Period" to estimate the expenses you paid on your account during this period. Expenses Paid on a $1,000 Investment in Pioneer Core Equity Fund Based on actual returns from January 1, 2017, through June 30, 2017. -------------------------------------------------------------------------------- Share Class A C Y -------------------------------------------------------------------------------- Beginning Account Value $1,000.00 $1,000.00 $1,000.00 on 1/1/17 -------------------------------------------------------------------------------- Ending Account Value $1,109.40 $1,104.50 $1,110.60 on 6/30/17 -------------------------------------------------------------------------------- Expenses Paid $ 4.65 $ 8.97 $ 3.30 During Period* -------------------------------------------------------------------------------- * Expenses are equal to the Fund's annualized net expense ratio of 0.89%, 1.72% and 0.63% for Class A, Class C and Class Y shares, respectively, multiplied by the average account value over the period, multiplied by 181/365 (to reflect the one-half year period). Pioneer Core Equity Fund | Semiannual Report | 6/30/17 15 Hypothetical Example for Comparison Purposes The table below provides information about hypothetical account values and hypothetical expenses based on the Fund's actual expense ratio and an assumed rate of return of 5% per year before expenses, which is not the Fund's actual return. The hypothetical account values and expenses may not be used to estimate the actual ending account balance or expenses you paid for the period. You may use this information to compare the ongoing costs of investing in the Fund and other funds. To do so, compare this 5% hypothetical example with the 5% hypothetical examples that appear in the shareholder reports of the other funds. Please note that the expenses shown in the tables are meant to highlight your ongoing costs only and do not reflect any transaction costs, such as sales charges (loads) that are charged at the time of the transaction. Therefore, the table below is useful in comparing ongoing costs only and will not help you determine the relative total costs of owning different funds. In addition, if these transaction costs were included, your costs would have been higher. Expenses Paid on a $1,000 Investment in Pioneer Core Equity Fund Based on a hypothetical 5% per year return before expenses, reflecting the period from January 1, 2017, through June 30, 2017. -------------------------------------------------------------------------------- Share Class A C Y -------------------------------------------------------------------------------- Beginning Account Value $1,000.00 $1,000.00 $1,000.00 on 1/1/17 -------------------------------------------------------------------------------- Ending Account Value $1,020.38 $1,016.27 $1,021.67 on 6/30/17 -------------------------------------------------------------------------------- Expenses Paid $ 4.46 $ 8.60 $ 3.16 During Period* -------------------------------------------------------------------------------- * Expenses are equal to the Fund's annualized net expense ratio of 0.89%, 1.72% and 0.63% for Class A, Class C and Class Y shares, respectively, multiplied by the average account value over the period, multiplied by 181/365 (to reflect the one-half year period). 16 Pioneer Core Equity Fund | Semiannual Report | 6/30/17 Schedule of Investments | 6/30/17 (unaudited) ---------------------------------------------------------------------------------------- Shares Value ---------------------------------------------------------------------------------------- COMMON STOCKS -- 98.3% ENERGY -- 6.5% Integrated Oil & Gas -- 4.6% 896,372 Exxon Mobil Corp. $ 72,364,112 ---------------------------------------------------------------------------------------- Oil & Gas Exploration & Production -- 1.9% 436,391 Cabot Oil & Gas Corp. $ 10,944,686 213,038 EOG Resources, Inc. 19,284,200 -------------- $ 30,228,886 -------------- Total Energy $ 102,592,998 ---------------------------------------------------------------------------------------- MATERIALS -- 4.8% Fertilizers & Agricultural Chemicals -- 1.4% 155,923 Agrium, Inc. $ 14,109,472 269,854 CF Industries Holdings, Inc. 7,545,118 -------------- $ 21,654,590 ---------------------------------------------------------------------------------------- Specialty Chemicals -- 1.8% 80,648 The Sherwin-Williams Co. $ 28,304,222 ---------------------------------------------------------------------------------------- Paper Packaging -- 1.6% 573,834 Sealed Air Corp. $ 25,684,810 -------------- Total Materials $ 75,643,622 ---------------------------------------------------------------------------------------- CAPITAL GOODS -- 6.6% Aerospace & Defense -- 2.3% 224,973 Raytheon Co. $ 36,328,640 ---------------------------------------------------------------------------------------- Building Products -- 2.2% 916,875 Masco Corp. $ 35,033,794 ---------------------------------------------------------------------------------------- Industrial Conglomerates -- 1.0% 156,352 Carlisle Companies, Inc. $ 14,915,981 ---------------------------------------------------------------------------------------- Trading Companies & Distributors -- 1.1% 159,138 United Rentals, Inc.* $ 17,936,444 -------------- Total Capital Goods $ 104,214,859 ---------------------------------------------------------------------------------------- TRANSPORTATION -- 2.9% Air Freight & Logistics -- 1.9% 271,502 United Parcel Service, Inc. (Class B) $ 30,025,406 ---------------------------------------------------------------------------------------- Trucking -- 1.0% 177,504 JB Hunt Transport Services, Inc. $ 16,220,316 -------------- Total Transportation $ 46,245,722 ---------------------------------------------------------------------------------------- AUTOMOBILES & COMPONENTS -- 1.1% Auto Parts & Equipment -- 1.1% 198,609 Delphi Automotive Plc $ 17,408,079 -------------- Total Automobiles & Components $ 17,408,079 ---------------------------------------------------------------------------------------- The accompanying notes are an integral part of these financial statements. Pioneer Core Equity Fund | Semiannual Report | 6/30/17 17 Schedule of Investments | 6/30/17 (unaudited) (continued) ---------------------------------------------------------------------------------------- Shares Value ---------------------------------------------------------------------------------------- CONSUMER DURABLES & APPAREL -- 1.4% Footwear -- 1.4% 379,651 NIKE, Inc. (Class B) $ 22,399,409 -------------- Total Consumer Durables & Apparel $ 22,399,409 ---------------------------------------------------------------------------------------- CONSUMER SERVICES -- 2.8% Restaurants -- 2.8% 750,580 Starbucks Corp. $ 43,766,320 -------------- Total Consumer Services $ 43,766,320 ---------------------------------------------------------------------------------------- MEDIA -- 3.3% Cable & Satellite -- 3.3% 1,359,156 Comcast Corp. $ 52,898,352 -------------- Total Media $ 52,898,352 ---------------------------------------------------------------------------------------- RETAILING -- 7.9% General Merchandise Stores -- 2.1% 457,605 Dollar General Corp.* $ 32,988,744 ---------------------------------------------------------------------------------------- Apparel Retail -- 1.1% 242,821 The TJX Companies, Inc. $ 17,524,392 ---------------------------------------------------------------------------------------- Home Improvement Retail -- 2.9% 299,245 The Home Depot, Inc. $ 45,904,183 ---------------------------------------------------------------------------------------- Automotive Retail -- 1.8% 129,959 O'Reilly Automotive, Inc.* $ 28,427,232 -------------- Total Retailing $ 124,844,551 ---------------------------------------------------------------------------------------- FOOD & STAPLES RETAILING -- 1.4% Drug Retail -- 1.4% 283,355 CVS Health Corp. $ 22,798,743 -------------- Total Food & Staples Retailing $ 22,798,743 ---------------------------------------------------------------------------------------- FOOD, BEVERAGE & TOBACCO -- 3.9% Packaged Foods & Meats -- 3.9% 233,744 McCormick & Co., Inc. $ 22,792,377 367,608 The Hershey Co. 39,470,071 -------------- $ 62,262,448 -------------- Total Food, Beverage & Tobacco $ 62,262,448 ---------------------------------------------------------------------------------------- HEALTH CARE EQUIPMENT & SERVICES -- 5.1% Health Care Supplies -- 2.0% 132,220 The Cooper Companies, Inc. $ 31,656,112 ---------------------------------------------------------------------------------------- The accompanying notes are an integral part of these financial statements. 18 Pioneer Core Equity Fund | Semiannual Report | 6/30/17 ---------------------------------------------------------------------------------------- Shares Value ---------------------------------------------------------------------------------------- Managed Health Care -- 3.1% 336,795 Centene Corp.* $ 26,903,185 94,109 Humana, Inc. 22,644,508 -------------- $ 49,547,693 -------------- Total Health Care Equipment & Services $ 81,203,805 ---------------------------------------------------------------------------------------- PHARMACEUTICALS, BIOTECHNOLOGY & LIFE SCIENCES -- 8.3% Biotechnology -- 4.4% 196,549 Celgene Corp.* $ 25,525,819 434,755 Gilead Sciences, Inc.* 30,771,959 100,974 Vertex Pharmaceuticals, Inc.* 13,012,519 -------------- $ 69,310,297 ---------------------------------------------------------------------------------------- Pharmaceuticals -- 3.9% 100,943 Jazz Pharmaceuticals Plc* $ 15,696,636 1,349,681 Pfizer, Inc. 45,335,785 -------------- $ 61,032,421 -------------- Total Pharmaceuticals, Biotechnology & Life Sciences $ 130,342,718 ---------------------------------------------------------------------------------------- BANKS -- 9.2% Diversified Banks -- 6.8% 780,844 Citigroup, Inc. $ 52,222,847 592,097 JPMorgan Chase & Co. 54,117,666 -------------- $ 106,340,513 ---------------------------------------------------------------------------------------- Regional Banks -- 2.4% 307,349 The PNC Financial Services Group, Inc. $ 38,378,670 -------------- Total Banks $ 144,719,183 ---------------------------------------------------------------------------------------- DIVERSIFIED FINANCIALS -- 3.7% Specialized Finance -- 1.2% 280,844 Intercontinental Exchange, Inc. $ 18,513,236 ---------------------------------------------------------------------------------------- Asset Management & Custody Banks -- 1.2% 46,593 BlackRock, Inc. $ 19,681,349 ---------------------------------------------------------------------------------------- Investment Banking & Brokerage -- 1.3% 463,941 The Charles Schwab Corp. $ 19,930,905 -------------- Total Diversified Financials $ 58,125,490 ---------------------------------------------------------------------------------------- INSURANCE -- 1.8% Insurance Brokers -- 1.8% 356,740 Marsh & McLennan Companies, Inc. $ 27,811,450 -------------- Total Insurance $ 27,811,450 ---------------------------------------------------------------------------------------- The accompanying notes are an integral part of these financial statements. Pioneer Core Equity Fund | Semiannual Report | 6/30/17 19 Schedule of Investments | 6/30/17 (unaudited) (continued) ---------------------------------------------------------------------------------------- Shares Value ---------------------------------------------------------------------------------------- SOFTWARE & SERVICES -- 13.1% Internet Software & Services -- 5.3% 53,283 Alphabet, Inc. (Class A) $ 49,536,139 7,147 Alphabet, Inc. (Class C) 6,494,693 784,725 eBay, Inc.* 27,402,597 -------------- $ 83,433,429 ---------------------------------------------------------------------------------------- IT Consulting & Other Services -- 1.3% 313,878 Cognizant Technology Solutions Corp.* $ 20,841,499 ---------------------------------------------------------------------------------------- Data Processing & Outsourced Services -- 2.9% 494,483 Visa, Inc. $ 46,372,616 ---------------------------------------------------------------------------------------- Systems Software -- 3.6% 816,859 Microsoft Corp. $ 56,306,091 -------------- Total Software & Services $ 206,953,635 ---------------------------------------------------------------------------------------- TECHNOLOGY HARDWARE & EQUIPMENT -- 8.0% Communications Equipment -- 2.2% 1,125,941 Cisco Systems, Inc. $ 35,241,953 ---------------------------------------------------------------------------------------- Computer Storage & Peripherals -- 4.6% 508,376 Apple, Inc. $ 73,216,312 ---------------------------------------------------------------------------------------- Technology Distributors -- 1.2% 293,533 CDW Corp./DE* $ 18,354,618 -------------- Total Technology Hardware & Equipment $ 126,812,883 ---------------------------------------------------------------------------------------- SEMICONDUCTORS & SEMICONDUCTOR EQUIPMENT -- 2.3% Semiconductors -- 2.3% 622,084 Micron Technology, Inc.* $ 18,575,428 493,260 Taiwan Semiconductor Manufacturing Co., Ltd. (A.D.R.) 17,244,370 -------------- $ 35,819,798 -------------- Total Semiconductors & Semiconductor Equipment $ 35,819,798 ---------------------------------------------------------------------------------------- TELECOMMUNICATION SERVICES -- 1.0% Integrated Telecommunication Services -- 1.0% 678,693 CenturyLink, Inc. $ 16,207,189 -------------- Total Telecommunication Services $ 16,207,189 ---------------------------------------------------------------------------------------- UTILITIES -- 3.2% Electric Utilities -- 3.2% 730,706 American Electric Power Co., Inc. $ 50,762,145 -------------- Total Utilities $ 50,762,145 ---------------------------------------------------------------------------------------- TOTAL COMMON STOCKS (Cost $1,330,476,807) $1,553,833,399 ---------------------------------------------------------------------------------------- The accompanying notes are an integral part of these financial statements. 20 Pioneer Core Equity Fund | Semiannual Report | 6/30/17 ---------------------------------------------------------------------------------------- Principal Amount ($) Value ---------------------------------------------------------------------------------------- U.S. GOVERNMENT AND AGENCY OBLIGATION -- 0.4% 5,930,000 U.S. Treasury Bill 7/6/17 (b) $ 5,929,626 ---------------------------------------------------------------------------------------- TOTAL U.S. GOVERNMENT AND AGENCY OBLIGATION (Cost $5,929,321) $ 5,929,626 ---------------------------------------------------------------------------------------- TOTAL INVESTMENT IN SECURITIES -- 98.7% (Cost $1,336,406,128) (a) $1,559,763,025 ---------------------------------------------------------------------------------------- OTHER ASSETS & LIABILITIES -- 1.3% $ 19,931,524 ---------------------------------------------------------------------------------------- TOTAL NET ASSETS -- 100.0% $1,579,694,549 ======================================================================================== * Non-income producing security. (A.D.R.) American Depositary Receipts. (a) At June 30, 2017, the net unrealized appreciation on investments based on cost for federal income tax purposes of $1,338,219,578 was as follows: Aggregate gross unrealized appreciation for all investments in which there is an excess of value over tax cost $ 231,684,073 Aggregate gross unrealized depreciation for all investments in which there is an excess of tax cost over value (10,140,626) ------------- Net unrealized appreciation $ 221,543,447 ============= Purchases and sales of securities (excluding temporary cash investments) for the six months ended June 30, 2017, aggregated $758,787,717 and $814,709,715, respectively. The Fund is permitted to engage in purchase and sale transactions ("cross trades") with certain Funds and accounts for which Amundi Pioneer Asset Management, Inc., (Amundi Pioneer) formerly Pioneer Investment Management, Inc. (PIM), serves as the Fund's investment adviser, as set forth in Rule 17a-7 under the Investment Company Act of 1940, pursuant to procedures adopted by the Board of Trustees. Under these procedures, cross trades are effected at current market prices. During the six months ended June 30, 2017, the Fund did not engage in cross trade activity. Various inputs are used in determining the value of the Fund's investments. These inputs are summarized in the three broad levels listed below. Level 1 - quoted prices in active markets for identical securities. Level 2 - other significant observable inputs (including quoted prices for similar securities, interest rates, prepayment speeds, credit risk, etc.) See Notes to Financial Statements -- Note 1A. Level 3 - significant unobservable inputs (including the Fund's own assumptions in determining fair value of investments) See Notes to Financial Statements -- Note 1A. The following is a summary of the inputs used as of June 30, 2017, in valuing the Fund's investments: ------------------------------------------------------------------------------------------------- Level 1 Level 2 Level 3 Total ------------------------------------------------------------------------------------------------- Common Stocks $ 1,553,833,399 $ -- $ -- $1,553,833,399 U.S. Government and Agency Obligation -- 5,929,626 -- 5,929,626 ------------------------------------------------------------------------------------------------- Total $ 1,553,833,399 $5,929,626 $ -- $1,559,763,025 ================================================================================================= During the six months ended June 30, 2017, there were no transfers between Levels 1, 2 and 3. The accompanying notes are an integral part of these financial statements. Pioneer Core Equity Fund | Semiannual Report | 6/30/17 21 Statement of Assets and Liabilities | 6/30/17 (unaudited) ASSETS: Investment in securities (cost $1,336,406,128) $ 1,559,763,025 Cash 4,337,776 Receivables -- Investment securities sold 42,613,152 Fund shares sold 214,531 Dividends 1,078,473 -------------------------------------------------------------------------------------------- Total assets $ 1,608,006,957 ============================================================================================ LIABILITIES: Payables -- Investment securities purchased $ 26,280,192 Fund shares repurchased 1,233,208 Distributions 67,918 Trustee fees 2,525 Due to affiliates 335,022 Accrued expenses 393,543 -------------------------------------------------------------------------------------------- Total liabilities $ 28,312,408 ============================================================================================ NET ASSETS: Paid-in capital $ 1,277,576,531 Undistributed net investment income 7,065,944 Accumulated net realized gain on investments and futures contracts 71,695,177 Net unrealized appreciation on investments 223,356,897 -------------------------------------------------------------------------------------------- Net assets $ 1,579,694,549 ============================================================================================ NET ASSET VALUE PER SHARE: (No par value, unlimited number of shares authorized) Class A (based on $1,518,225,825/75,997,229 shares) $ 19.98 Class C (based on $13,491,815/755,596 shares) $ 17.86 Class Y (based on $47,976,909/2,376,316 shares) $ 20.19 MAXIMUM OFFERING PRICE: Class A ($19.98 (divided by) 94.25%) $ 21.20 ============================================================================================ The accompanying notes are an integral part of these financial statements. 22 Pioneer Core Equity Fund | Semiannual Report | 6/30/17 Statement of Operations (unaudited) For the Six Months Ended 6/30/17 INVESTMENT INCOME: Dividends (net of withholding tax of $155,470) $ 13,547,994 Interest 84,515 ----------------------------------------------------------------------------------------------- Total investment income $ 13,632,509 ----------------------------------------------------------------------------------------------- EXPENSES: Management fees $ 3,867,523 Transfer agent fees Class A 469,702 Class C 8,431 Class Y 15,989 Distribution fees Class A 1,857,891 Class C 68,971 Shareholder communications expense 117,354 Administrative expense 308,128 Custodian fees 15,947 Registration fees 27,508 Professional fees 33,381 Printing expense 14,047 Fees and expenses of nonaffiliated Trustees 39,528 Miscellaneous 44,066 ----------------------------------------------------------------------------------------------- Total expenses $ 6,888,466 ----------------------------------------------------------------------------------------------- Net investment income $ 6,744,043 ----------------------------------------------------------------------------------------------- REALIZED AND UNREALIZED GAIN (LOSS) ON INVESTMENTS AND FUTURES CONTRACTS: Net realized gain (loss) on: Investments $111,627,089 Futures contracts (99,315) $111,527,774 ----------------------------------------------------------------------------------------------- Change in net unrealized appreciation (depreciation) on investments $ 41,826,433 ----------------------------------------------------------------------------------------------- Net realized and unrealized gain (loss) on investments and futures contracts $153,354,207 ----------------------------------------------------------------------------------------------- Net increase in net assets resulting from operations $160,098,250 =============================================================================================== The accompanying notes are an integral part of these financial statements. Pioneer Core Equity Fund | Semiannual Report | 6/30/17 23 Statements of Changes in Net Assets ---------------------------------------------------------------------------------------------------- Six Months Ended 6/30/17 Year Ended (unaudited) 12/31/16 ---------------------------------------------------------------------------------------------------- FROM OPERATIONS: Net investment income (loss) $ 6,744,043 $ 16,856,119 Net realized gain (loss) on investments and futures contracts 111,527,774 47,430,069 Change in net unrealized appreciation (depreciation) on investments 41,826,433 53,203,971 ---------------------------------------------------------------------------------------------------- Net increase (decrease) in net assets resulting from operations $ 160,098,250 $ 117,490,159 ---------------------------------------------------------------------------------------------------- DISTRIBUTIONS TO SHAREOWNERS: Net investment income: Class A ($0.00 and $0.20 per share, respectively) $ -- $ (16,068,920) Class C ($0.00 and $0.09 per share, respectively) -- (69,203) Class Y ($0.00 and $0.25 per share, respectively) -- (623,537) ---------------------------------------------------------------------------------------------------- Total distributions to shareowners $ -- $ (16,761,660) ---------------------------------------------------------------------------------------------------- FROM FUND SHARE TRANSACTIONS: Net proceeds from sale of shares $ 17,849,385 $ 25,299,938 Reinvestment of distributions -- 15,467,606 Cost of shares repurchased (92,391,981) (174,484,709) ---------------------------------------------------------------------------------------------------- Net decrease in net assets resulting from Fund share transactions $ (74,542,596) $ (133,717,165) ---------------------------------------------------------------------------------------------------- Net increase (decrease) in net assets $ 85,555,654 $ (32,988,666) NET ASSETS: Beginning of period $ 1,494,138,895 $ 1,527,127,561 ---------------------------------------------------------------------------------------------------- End of period $ 1,579,694,549 $ 1,494,138,895 ==================================================================================================== Undistributed net investment income $ 7,065,944 $ 321,901 ==================================================================================================== The accompanying notes are an integral part of these financial statements. 24 Pioneer Core Equity Fund | Semiannual Report | 6/30/17 --------------------------------------------------------------------------------------------- Six Months Six Months Ended Ended 6/30/17 6/30/17 Year Ended Year Ended Shares Amount 12/31/16 12/31/16 (unaudited) (unaudited) Shares Amount --------------------------------------------------------------------------------------------- Class A Shares sold 530,526 $ 10,234,729 976,643 $ 16,421,975 Reinvestment of distributions -- -- 835,056 15,256,426 Less shares repurchased (4,265,753) (82,018,269) (8,452,628) (142,378,598) --------------------------------------------------------------------------------------------- Net decrease (3,735,227) $(71,783,540) (6,640,929) $(110,700,197) ============================================================================================= Class C Shares sold 95,178 $ 1,623,458 163,251 $ 2,510,542 Reinvestment of distributions -- -- 3,831 62,819 Less shares repurchased (144,721) (2,519,931) (295,427) (4,379,785) --------------------------------------------------------------------------------------------- Net decrease (49,543) $ (896,473) (128,345) $ (1,806,424) ============================================================================================= Class Y Shares sold 307,957 $ 5,991,198 368,360 $ 6,367,421 Reinvestment of distributions -- -- 8,046 148,361 Less shares repurchased (402,107) (7,853,781) (1,576,444) (27,726,326) --------------------------------------------------------------------------------------------- Net decrease (94,150) $ (1,862,583) (1,200,038) $ (21,210,544) ============================================================================================= The accompanying notes are an integral part of these financial statements. Pioneer Core Equity Fund | Semiannual Report | 6/30/17 25 Financial Highlights ---------------------------------------------------------------------------------------------------------------------------------- Six Months Ended Year Year Year Year Year 6/30/17 Ended Ended Ended Ended Ended (unaudited) 12/31/16 12/31/15 12/31/14 12/31/13(a) 12/31/12(a) ---------------------------------------------------------------------------------------------------------------------------------- Class A Net asset value, beginning of period $ 18.01 $ 16.80 $ 17.18 $ 15.70 $ 12.06 $ 10.61 ---------------------------------------------------------------------------------------------------------------------------------- Increase (decrease) from investment operations: Net investment income (loss) $ 0.08(b) $ 0.19(b) $ 0.13(b) $ 0.18 $ 0.10 $ 0.08 Net realized and unrealized gain (loss) on investments 1.89 1.22 (0.39) 1.46 3.63 1.45 ---------------------------------------------------------------------------------------------------------------------------------- Net increase (decrease) from investment operations $ 1.97 $ 1.41 $ (0.26) $ 1.64 $ 3.73 $ 1.53 ---------------------------------------------------------------------------------------------------------------------------------- Distribution to shareowners: Net investment income $ -- $ (0.20) $ (0.12) $ (0.16) $ (0.09) $ (0.08) ---------------------------------------------------------------------------------------------------------------------------------- Net increase (decrease) in net asset value $ 1.97 $ 1.21 $ (0.38) $ 1.48 $ 3.64 $ 1.45 ---------------------------------------------------------------------------------------------------------------------------------- Net asset value, end of period $ 19.98 $ 18.01 $ 16.80 $ 17.18 $ 15.70 $ 12.06 ================================================================================================================================== Total return* 10.94% 8.39% (1.49)%(d) 10.44% 31.02% 14.51% Ratio of net expenses to average net assets (c) 0.89%** 0.94% 0.93% 0.94% 0.99% 1.25% Ratio of net investment income (loss) to average net assets 0.87%** 1.15% 0.75% 1.03% 0.70% 0.76% Portfolio turnover rate 101%** 80% 100% 57% 67% 59% Net assets, end of period (in thousands) $1,518,226 $1,436,208 $1,450,815 $1,605,301 $1,585,294 $23,907 Ratios with no waiver of fees and assumption of expenses by Amundi Pioneer formerly PIM and no reduction for fees paid indirectly: Total expenses to average net assets (c) 0.89%** 0.94% 0.93% 0.94% 0.99% 1.59% Net investment income (loss) to average net assets 0.87%** 1.15% 0.75% 1.03% 0.70% 0.42% ================================================================================================================================== * Assumes initial investment at net asset value at the beginning of each period, reinvestment of all distributions, the complete redemption of the investment at net asset value at the end of each period and no sales charges. Total return would be reduced if sales charges were taken into account. ** Annualized. (a) The Fund acquired the assets and liabilities of Pioneer Research Fund (the "predecessor fund") on June 7, 2013 (the "reorganization"). As a result of the reorganization, the predecessor fund's performance and financial history became the performance and financial history of the Fund. Historical per-share amounts prior to June 7, 2013 have been adjusted to reflect the conversion ratio used to align the net asset values of the predecessor fund with those of the Fund. (b) The per share data presented above is based on the average shares outstanding for the period presented. (c) Includes interest expense of 0.00%, 0.00%, 0.00%, 0.00%+, 0.00% and 0.00%, respectively. (d) If the Fund had not recognized gains in settlement of class action lawsuits during the year ended December 31, 2015, the total return would have been (1.55)%. + Amount rounds to less than 0.01%. The accompanying notes are an integral part of these financial statements. 26 Pioneer Core Equity Fund | Semiannual Report | 6/30/17 ---------------------------------------------------------------------------------------------------------------------------------- Six Months Ended Year Year Year Year Year 6/30/17 Ended Ended Ended Ended Ended (unaudited) 12/31/16 12/31/15 12/31/14 12/31/13(a) 12/31/12(a) ---------------------------------------------------------------------------------------------------------------------------------- Class C Net asset value, beginning of period $ 16.17 $ 15.11 $ 15.48 $ 14.19 $ 10.93 $ 9.65 ---------------------------------------------------------------------------------------------------------------------------------- Increase (decrease) from investment operations: Net investment income (loss) $ (0.00)(b)(c)(f) $ 0.05(b) $ (0.01)(b)(c) $ 0.02 $ (0.02)(c) $ (0.01)(c) Net realized and unrealized gain (loss) on investments 1.69 1.10 (0.35) 1.33 3.28 1.30 ---------------------------------------------------------------------------------------------------------------------------------- Net increase (decrease) from investment operations $ 1.69 $ 1.15 $ (0.36) $ 1.35 $ 3.26 $ 1.29 ---------------------------------------------------------------------------------------------------------------------------------- Distribution to shareowners: Net investment income $ -- $ (0.09) $ (0.01) $ (0.06) $ -- $ (0.01) ---------------------------------------------------------------------------------------------------------------------------------- Net increase (decrease) in net asset value $ 1.69 $ 1.06 $ (0.37) $ 1.29 $ 3.26 $ 1.28 ---------------------------------------------------------------------------------------------------------------------------------- Net asset value, end of period $ 17.86 $ 16.17 $ 15.11 $ 15.48 $ 14.19 $ 10.93 ================================================================================================================================== Total return* 10.45% 7.58% (2.34)%(e) 9.52% 29.81% 13.37% Ratio of net expenses to average net assets (d) 1.72%** 1.76% 1.74% 1.81% 1.92% 2.15% Ratio of net investment income (loss) to average net assets 0.05%** 0.33% (0.06)% 0.14% (0.17)% (0.14)% Portfolio turnover rate 101%** 80% 100% 57% 67% 59% Net assets, end of period (in thousands) $13,492 $13,016 $14,106 $ 13,848 $11,112 $ 3,695 Ratios with no waiver of fees and assumption of expenses by Amundi Pioneer formerly PIM and no reduction for fees paid indirectly: Total expenses to average net assets (d) 1.72%** 1.76% 1.74% 1.81% 1.92% 2.31% Net investment income (loss) to average net assets 0.05%** 0.33% (0.06)% 0.14% (0.17)% (0.30)% ================================================================================================================================== * Assumes initial investment at net asset value at the beginning of each period, reinvestment of all distributions, the complete redemption of the investment at net asset value at the end of each period and no sales charges. Total return would be reduced if sales charges were taken into account. ** Annualized. (a) The Fund acquired the assets and liabilities of Pioneer Research Fund (the "predecessor fund") on June 7, 2013 (the "reorganization"). As a result of the reorganization, the predecessor fund's performance and financial history became the performance and financial history of the Fund. Historical per-share amounts prior to June 7, 2013 have been adjusted to reflect the conversion ratio used to align the net asset values of the predecessor fund with those of the Fund. (b) The per share data presented above is based on the average shares outstanding for the period presented. (c) The amount shown for a share outstanding does not correspond with the net investment gain on the Statement of Operations for the period due to timing of the sales and repurchase of shares. (d) Includes interest expense of 0.00%, 0.00%, 0.00%, 0.00%+, 0.00% and 0.00%, respectively. (e) If the Fund had not recognized gains in settlement of class action lawsuits during the year ended December 31, 2015, the total return would have been (2.40)%. (f) Amount rounds to less than $0.01 or $(0.01) per share. + Amount rounds to less than 0.01%. The accompanying notes are an integral part of these financial statements. Pioneer Core Equity Fund | Semiannual Report | 6/30/17 27 Financial Highlights (continued) ---------------------------------------------------------------------------------------------------------------------------------- Six Months Ended Year Year Year Year Year 6/30/17 Ended Ended Ended Ended Ended (unaudited) 12/31/16 12/31/15 12/31/14 12/31/13(a) 12/31/12(a) ---------------------------------------------------------------------------------------------------------------------------------- Class Y Net asset value, beginning of period $ 18.18 $ 16.95 $ 17.34 $ 15.85 $ 12.17 $ 10.69 ---------------------------------------------------------------------------------------------------------------------------------- Increase (decrease) from investment operations: Net investment income (loss) $ 0.11(b) $ 0.25(b) $ 0.19(b) $ 0.20 $ 0.14 $ 0.11 Net realized and unrealized gain (loss) on investments 1.90 1.23 (0.40) 1.51 3.68 1.47 ---------------------------------------------------------------------------------------------------------------------------------- Net increase (decrease) from investment operations $ 2.01 $ 1.48 $ (0.21) $ 1.71 $ 3.82 $ 1.58 ---------------------------------------------------------------------------------------------------------------------------------- Distribution to shareowners: Net investment income $ -- $ (0.25) $ (0.18) $ (0.22) $ (0.14) $ (0.10) ---------------------------------------------------------------------------------------------------------------------------------- Net increase (decrease) in net asset value $ 2.01 $ 1.23 $ (0.39) $ 1.49 $ 3.68 $ 1.48 ---------------------------------------------------------------------------------------------------------------------------------- Net asset value, end of period $ 20.19 $ 18.18 $ 16.95 $ 17.34 $ 15.85 $ 12.17 ================================================================================================================================== Total return* 11.06% 8.73% (1.21)%(d) 10.75% 31.49% 14.81% Ratio of net expenses to average net assets (c) 0.63%** 0.63% 0.62% 0.63% 0.75% 1.02% Ratio of net investment income (loss) to average net assets 1.13%** 1.47% 1.07% 1.37% 1.01% 0.97% Portfolio turnover rate 101%** 80% 100% 57% 67% 59% Net assets, end of period (in thousands) $ 47,977 $44,915 $62,206 $66,424 $59,812 $33,875 ================================================================================================================================== * Assumes initial investment at net asset value at the beginning of each period, reinvestment of all distributions and the complete redemption of the investment at net asset value at the end of each period. ** Annualized. (a) The Fund acquired the assets and liabilities of Pioneer Research Fund (the "predecessor fund") on June 7, 2013 (the "reorganization"). As a result of the reorganization, the predecessor fund's performance and financial history became the performance and financial history of the Fund. Historical per-share amounts prior to June 7, 2013 have been adjusted to reflect the conversion ratio used to align the net asset values of the predecessor fund with those of the Fund. (b) The per share data presented above is based on the average shares outstanding for the period presented. (c) Includes interest expense of 0.00%, 0.00%, 0.00%, 0.00%+, 0.00% and 0.00%, respectively. (d) If the Fund had not recognized gains in settlement of class action lawsuits during the year ended December 31, 2015, the total return would have been (1.27)%. + Amount rounds to less than 0.01%. The accompanying notes are an integral part of these financial statements. 28 Pioneer Core Equity Fund | Semiannual Report | 6/30/17 Notes to Financial Statements | 6/30/17 (unaudited) 1. Organization and Significant Accounting Policies Pioneer Core Equity Fund (the Fund) is a diversified series of Pioneer Series Trust XI, a Delaware statutory trust registered under the Investment Company Act of 1940 as an open-end management investment company. The investment objective of the Fund is to seek long-term capital growth. The Fund offers three classes of shares designated as Class A, Class C and Class Y shares. Each class of shares represents an interest in the same portfolio of investments of the Fund and has identical rights (based on relative net asset values) to assets and liquidation proceeds. Share classes can bear different rates of class-specific fees and expenses such as transfer agent and distribution fees. Differences in class-specific fees and expenses will result in differences in net investment income and, therefore, the payment of different dividends from net investment income earned by each class. The Amended and Restated Declaration of Trust of the Fund gives the Board of Trustees the flexibility to specify either per-share voting or dollar-weighted voting when submitting matters for shareholder approval. Under per-share voting, each share of a class of the Fund is entitled to one vote. Under dollar-weighted voting, a shareholder's voting power is determined not by the number of shares owned, but by the dollar value of the shares on the record date. Each share class has exclusive voting rights with respect to matters affecting only that class, including with respect to the distribution plan for that class. There is no distribution plan for Class Y shares. On July 3, 2017, Amundi acquired Pioneer Investments, a group of asset management companies located throughout the world. Amundi, one of the world's largest asset managers, is headquartered in Paris, France. As a result of the transaction, Pioneer Investment Management, Inc., the Fund's investment adviser, became an indirect wholly owned subsidiary of Amundi and Amundi's wholly owned subsidiary, Amundi USA, Inc. Prior to July 3, 2017, Pioneer Investments was owned by Pioneer Global Asset Management S.p.A., a wholly owned subsidiary of UniCredit S.p.A. In connection with the transaction, the names of the Fund's investment adviser and principal underwriter changed. Effective July 3, 2017, the name of Pioneer Investment Management, Inc. changed to Amundi Pioneer Asset Management, Inc. and the name of Pioneer Funds Distributor, Inc. changed to Amundi Pioneer Distributor, Inc. The Fund's financial statements have been prepared in conformity with U.S. generally accepted accounting principles (U.S. GAAP) that require the management of the Fund to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets Pioneer Core Equity Fund | Semiannual Report | 6/30/17 29 and liabilities at the date of the financial statements, and the reported amounts of income, expenses and gain or loss on investments during the reporting period. Actual results could differ from those estimates. The Fund is an investment company and follows investment company accounting and reporting guidance under U.S. GAAP. The following is a summary of significant accounting policies followed by the Fund in the preparation of its financial statements: A. Security Valuation The net asset value of the Fund is computed once daily, on each day the New York Stock Exchange (NYSE) is open, as of the close of regular trading on the NYSE. Equity securities that have traded on an exchange are valued by using the last sale price on the principal exchange where they are traded. Equity securities that have not traded on the date of valuation, or securities for which sale prices are not available, generally are valued using the mean between the last bid and asked prices or, if both last bid and asked prices are not available, at the last quoted bid price. Last sale and bid and asked prices are provided by independent third party pricing services. In the case of equity securities not traded on an exchange, prices are typically determined by independent third party pricing services using a variety of techniques and methods. The value of foreign securities is translated into U.S. dollars based on foreign currency exchange rate quotations supplied by a third party pricing source. Trading in non-U.S. equity securities is substantially completed each day at various times prior to the close of the NYSE. The values of such securities used in computing the net asset value of the Fund's shares are determined as of such times. The Fund may use a fair value model developed by an independent pricing service to value non-U.S. equity securities. Securities for which independent pricing services or broker-dealers are unable to supply prices or for which market prices and/or quotations are not readily available or are considered to be unreliable are valued by a fair valuation team comprised of certain personnel of Amundi Pioneer Asset Management, Inc., (Amundi Pioneer), formerly Pioneer Investment Management, Inc. (PIM), the Fund's investment adviser, pursuant to procedures adopted by the Fund's Board of Trustees. Amundi Pioneer's, formerly PIM's, fair valuation team uses fair value methods approved by the Valuation Committee of the Board of Trustees. Amundi Pioneer's, formerly PIM's, fair valuation team is responsible for monitoring developments that may impact fair valued securities and for discussing and assessing fair values on an ongoing basis, and at least quarterly, with the Valuation Committee of the Board of Trustees. 30 Pioneer Core Equity Fund | Semiannual Report | 6/30/17 Inputs used when applying fair value methods to value a security may include credit ratings, the financial condition of the company, current market conditions and comparable securities. The Fund may use fair value methods if it is determined that a significant event has occurred after the close of the exchange or market on which the security trades and prior to the determination of the Fund's net asset value. Examples of a significant event might include political or economic news, corporate restructurings, natural disasters, terrorist activity or trading halts. Thus, the valuation of the Fund's securities may differ significantly from exchange prices and such differences could be material. At June 30, 2017, there were no securities valued using fair value methods (other than securities valued using prices supplied by independent pricing services). B. Investment Income and Transactions Dividend income is recorded on the ex-dividend date, except that certain dividends from foreign securities where the ex-dividend date may have passed are recorded as soon as the Fund becomes aware of the ex-dividend data in the exercise of reasonable diligence. Interest income, including interest on income bearing cash accounts, is recorded on the accrual basis. Dividend and interest income are reported net of unrecoverable foreign taxes withheld at the applicable country rates. Security transactions are recorded as of trade date. Gains and losses on sales of investments are calculated on the identified cost method for both financial reporting and federal income tax purposes. C. Foreign Currency Translation The books and records of the Fund are maintained in U.S. dollars. Amounts denominated in foreign currencies are translated into U.S. dollars using current exchange rates. Net realized gains and losses on foreign currency transactions, if any, represent, among other things, the net realized gains and losses on foreign currency contracts, disposition of foreign currencies and the difference between the amount of income accrued and the U.S. dollars actually received. Further, the effects of changes in foreign currency exchange rates on investments are not segregated in the Statement of Operations from the effects of changes in the market prices of those securities, but are included with the net realized and unrealized gain or loss on investments. Pioneer Core Equity Fund | Semiannual Report | 6/30/17 31 D. Federal Income Taxes It is the Fund's policy to comply with the requirements of the Internal Revenue Code applicable to regulated investment companies and to distribute all of its net taxable income and net realized capital gains, if any, to its shareowners. Therefore, no provision for federal income taxes is required. As of December 31, 2016, the Fund did not accrue any interest or penalties with respect to uncertain tax positions, which, if applicable, would be recorded as an income tax expense in the Statement of Operations. Tax returns filed within the prior three years remain subject to examination by Federal and State tax authorities. The amount and character of income and capital gain distributions to shareowners are determined in accordance with federal income tax rules, which may differ from U.S. GAAP. Distributions in excess of net investment income or net realized gains are temporary overdistributions for financial statement purposes resulting from differences in the recognition or classification of income or distributions for financial statement and tax purposes. Capital accounts within the financial statements are adjusted for permanent book/tax differences to reflect tax character, but are not adjusted for temporary differences. The tax character of current year distributions payable will be determined at the end of the current taxable year. The tax character of distributions paid during the year ended December 31, 2016 was as follows: ---------------------------------------------------------------------------- 2016 ---------------------------------------------------------------------------- Distributions paid from: Ordinary income $ 16,761,660 ---------------------------------------------------------------------------- Total $ 16,761,660 ============================================================================ The following shows components of distributable earnings on a federal income tax basis at December 31, 2016: ---------------------------------------------------------------------------- 2016 ---------------------------------------------------------------------------- Distributable earnings: Undistributed ordinary income $ 321,901 Capital loss carryforward (38,019,147) Net unrealized appreciation 179,717,014 ---------------------------------------------------------------------------- Total $142,019,768 ============================================================================ The difference between book-basis and tax-basis net unrealized appreciation is attributable to the tax deferral of losses on wash sales. 32 Pioneer Core Equity Fund | Semiannual Report | 6/30/17 E. Fund Shares The Fund records sales and repurchases of its shares as of trade date. Amundi Pioneer Distributor, Inc., formerly Pioneer Funds Distributor, Inc. (PFD), the principal underwriter for the Fund and a wholly owned indirect subsidiary of UniCredit, earned $28,669 in underwriting commissions on the sale of Class A shares during the six months ended June 30, 2017. F. Class Allocations Income, common expenses and realized and unrealized gains and losses are calculated at the Fund level and allocated daily to each class of shares based on its respective percentage of adjusted net assets at the beginning of the day. Distribution fees are calculated based on the average daily net asset value attributable to Class A and Class C shares of the Fund, respectively (see Note 4). Class Y shares do not pay distribution fees. All expenses and fees paid to the Fund's transfer agent for its services are allocated among the classes of shares based on the number of accounts in each class and the ratable allocation of related out-of-pocket expenses (see Note 3). Distributions to shareowners are recorded as of the ex-dividend date. Distributions paid by the Fund with respect to each class of shares are calculated in the same manner and at the same time, except that net investment income dividends to Class A, Class C and Class Y shares can reflect different transfer agent and distribution expense rates. G. Risks All investments are subject to risk, including the possible loss of principal. In the past several years, financial markets have experienced increased volatility, depressed valuations, decreased liquidity and heightened uncertainty. These conditions may continue, recur, worsen or spread. At times, the Fund's investments may represent industries or industry sectors that are interrelated or have common risks, making the Fund more susceptible to any economic, political, or regulatory developments or other risks affecting those industries and sectors. The Fund's prospectus contains unaudited information regarding the Fund's principal risks. Please refer to that document when considering the Fund's principal risks. H. Futures Contracts The Fund may enter into futures transactions in order to attempt to hedge against changes in interest rates, securities prices and currency exchange rates or to seek to increase total return. Futures contracts are types of derivatives. All futures contracts entered into by the Fund are traded on a futures exchange. Upon entering into a futures contract, the Fund is required to deposit with a broker an amount of cash or securities equal to the minimum Pioneer Core Equity Fund | Semiannual Report | 6/30/17 33 "initial margin" requirements of the associated futures exchange. Subsequent payments for futures contracts ("variation margin") are paid or received by the Fund, depending on the daily fluctuation in the value of the contracts, and are recorded by the Fund as unrealized appreciation or depreciation. When the contract is closed, the Fund realizes a gain or loss equal to the difference between the opening and closing value of the contract as well as any fluctuation in foreign currency exchange rates where applicable. Futures contracts are subject to market risk, interest rate risk and currency exchange rate risk. Changes in value of the contracts may not directly correlate to the changes in value of the underlying securities. The average value of contracts open during the six months ended June 30, 2017 was $7,443,544. There were no open futures contracts at June 30, 2017. 2. Management Agreement Amundi Pioneer, formerly PIM manages the Fund's portfolio. Management fees are calculated daily at the annual rate of 0.50% of the Fund's average daily net assets. For the six months ended June 30, 2017, the net management fee (excluding waivers and/or assumption of expenses) was equivalent to 0.50% of the Fund's average daily net assets. In addition, under the management and administration agreements, certain other services and costs, including accounting, regulatory reporting and insurance premiums, are paid by the Fund as administrative reimbursements. Included in "Due to affiliates" reflected on the Statement of Assets and Liabilities is $226,863 in management fees, administrative costs and certain other reimbursements payable to Amundi Pioneer, formerly PIM at June 30, 2017. 3. Transfer Agent Boston Financial Data Services, Inc. serves as the transfer agent to the Fund at negotiated rates. Transfer agent fees and payables shown on the Statement of Operations and the Statement of Assets and Liabilities, respectively, include sub-transfer agent expenses incurred through the Fund's omnibus relationship contracts. In addition, the Fund reimbursed the transfer agent for out-of-pocket expenses incurred by the transfer agent related to shareholder communications activities such as proxy and statement mailings and outgoing phone calls. For the six months ended June 30, 2017, such out-of-pocket expenses by class of shares were as follows: -------------------------------------------------------------------------------- Shareholder Communications: -------------------------------------------------------------------------------- Class A $ 114,675 Class C 2,419 Class Y 260 -------------------------------------------------------------------------------- Total $ 117,354 ================================================================================ 34 Pioneer Core Equity Fund | Semiannual Report | 6/30/17 4. Distribution Plan The Fund has adopted a distribution plan (the Plan) pursuant to Rule 12b-1 of the Investment Company Act of 1940 with respect to its Class A and Class C shares. Pursuant to the Plan, the Fund pays Amundi Pioneer Distributor, Inc., formerly PFD 0.25% of the average daily net assets attributable to Class A shares as compensation for personal services and/or account maintenance services or distribution services with regard to Class A shares. Pursuant to the Plan, the Fund also pays Amundi Pioneer Distributor, Inc., formerly PFD 1.00% of the average daily net assets attributable to Class C shares. The fee for Class C shares consists of a 0.25% service fee and a 0.75% distribution fee paid as compensation for personal services and/or account maintenance services or distribution services with regard to Class C shares. Included in "Due to affiliates" reflected on the Statement of Assets and Liabilities is $108,159 in distribution fees payable to Amundi Pioneer Distributor, Inc., formerly PFD at June 30, 2017. In addition, redemptions of each class of shares (except Class Y shares) may be subject to a contingent deferred sales charge (CDSC). A CDSC of 1.00% may be imposed on redemptions of certain net asset value purchases of Class A shares within 12 months of purchase. Redemptions of Class C shares within 12 months of purchase are subject to a CDSC of 1.00%, based on the lower of cost or market value of shares being redeemed. Shares purchased as part of an exchange remain subject to any CDSC that applied to the original purchase of those shares. There is no CDSC for Class Y shares. Proceeds from the CDSC are paid to Amundi Pioneer Distributor, Inc., formerly PFD. For the six months ended June 30, 2017, CDSC in the amount of $664 were paid to Amundi Pioneer Distributor, Inc., formerly PFD. 5. Line of Credit Facility The Fund, along with certain other funds in the Pioneer Family of Funds (the Funds), participates in a committed, unsecured revolving line of credit facility. Borrowings are used solely for temporary or emergency purposes. The Fund may borrow up to the lesser of the amount available under the facility or the limits set for borrowing by the Fund's prospectus and the 1940 Act. The credit facility in which the Fund participated until February 9, 2016 was in the amount of $240 million. The credit facility in which the Fund participated until February 7, 2017, was in the amount of $220 million. Effective February 8, 2017, the Fund participated in a facility that is in the amount of $195 million. Under such facility, depending on the type of loan, interest on borrowings is payable at the London Interbank Offered Rate (LIBOR) plus 0.85% on an annualized basis, or the Alternate Base Rate, which is the greater of (a) the facility's administrative agent's daily announced prime rate on the borrowing date, (b) 2% plus the Federal Funds Rate on the borrowing date and (c) 2% plus the overnight Eurodollar rate on the borrowing date. The Funds Pioneer Core Equity Fund | Semiannual Report | 6/30/17 35 pay an annual commitment fee to participate in a credit facility. The commitment fee is allocated among participating Funds based on an allocation schedule set forth in the credit agreement. For the six months ended June 30, 2017, the Fund had no borrowings under the credit facility. 6. Additional Disclosures about Derivative Instruments and Hedging Activities The Fund's use of derivatives subjects it to the following risks: Interest rate risk relates to the fluctuations in the value of interest-bearing securities due to changes in the prevailing levels of market interest rates. Credit risk relates to the ability of the issuer of a financial instrument to make further principal or interest payments on an obligation or commitment that it has to the Fund. Foreign exchange rate risk relates to fluctuations in the value of an asset or liability due to changes in currency exchange rates. Equity risk relates to the fluctuations in the value of financial instruments as a result of changes in market prices (other than those arising from interest rate risk or foreign exchange risk), whether caused by factors specific to an individual investment, its issuer, or all factors affecting all instruments traded in a market or market segment. Commodity risk relates to the risk that the value of a commodity or commodity index will fluctuate based on increases or decreases in the commodities market and factors specific to a particular industry or commodity. The effect of derivative instruments (not considered to be hedging instruments for accounting disclosure purposes) on the Statement of Operations by risk exposure at June 30, 2017 was as follows: --------------------------------------------------------------------------------- Statement of Operations Foreign Interest Credit Exchange Equity Commodity Rate Risk Risk Rate Risk Risk Risk --------------------------------------------------------------------------------- Net realized gain (loss) on Futures contracts $ -- $ -- $ -- $ (99,315) $ -- --------------------------------------------------------------------------------- Total Value $ -- $ -- $ -- $ (99,315) $ -- ================================================================================= 36 Pioneer Core Equity Fund | Semiannual Report | 6/30/17 7. Results of Shareholder Meeting At a special meeting held on June 13, 2017, shareholders of the Fund were asked to consider the proposals described below. A report of the total votes cast by the Fund's shareholders follows: -------------------------------------------------------------------------------------------------- For Against Abstain Broker Non-Votes -------------------------------------------------------------------------------------------------- Proposal 1 - To approve 38,548,938.917 1,533,432.598 2,574,093.433 4,260,114.000 a New Management Agreement with the Adviser ------------------------------------------------------------------------------------------- For Withhold ------------------------------------------------------------------------------------------- Proposal 2 - To elect Trustees ------------------------------------------------------------------------------------------- David R. Bock 44,984,657.790 1,931,921.158 ------------------------------------------------------------------------------------------- Benjamin M. Friedman 44,825,729.502 2,090,849.446 ------------------------------------------------------------------------------------------- Margaret B.W. Graham 44,923,396.418 1,993,182.530 ------------------------------------------------------------------------------------------- Lisa M. Jones 45,019,721.835 1,896,857.113 ------------------------------------------------------------------------------------------- Lorraine H. Monchak 44,863,646.305 2,052,932.643 ------------------------------------------------------------------------------------------- Thomas J. Perna 44,946,949.575 1,969,629.373 ------------------------------------------------------------------------------------------- Marguerite A. Piret 44,682,444.149 2,234,134.799 ------------------------------------------------------------------------------------------- Fred J. Ricciardi 44,784,799.755 2,131,779.193 ------------------------------------------------------------------------------------------- Kenneth J. Taubes 44,961,541.535 1,955,037.413 ------------------------------------------------------------------------------------------- ------------------------------------------------------------------------------------------------ For Against Abstain Broker Non-Votes ------------------------------------------------------------------------------------------------ Proposal 3 - To convert 33,230,899.784 4,381,650.955 5,043,910.209 4,260,118.000 investment objective(s) from fundamental to non-fundamental Pioneer Core Equity Fund | Semiannual Report | 6/30/17 37 Additional Information Change in Independent Registered Public Accounting Firm Prior to July 3, 2017 Pioneer Investment Management, Inc. (the "Adviser"), the Fund's investment adviser, was an indirect, wholly owned subsidiary of UniCredit S.p.A. ("UniCredit"). On that date, UniCredit completed the sale of its Pioneer Investments business, which includes the Adviser, to Amundi (the "Transaction"). As a result of the Transaction, the Adviser became an indirect, wholly-owned subsidiary of Amundi. Amundi is controlled by Credit Agricole S.A. Amundi is headquartered in Paris, France, and, as of September 30, 2016, had more than $1.1 trillion in assets under management worldwide. Deloitte & Touche LLP ("D&T"), the Fund's previous independent registered public accounting firm, informed the Audit Committee and the Board that it would no longer be independent with respect to the Fund upon the completion of the Transaction as a result of certain services being provided to Amundi and Credit Agricole, and, accordingly, that it intended to resign as the Fund's independent registered public accounting firm upon the completion of the Transaction. D&T's resignation was effective on July 3, 2017, when the Transaction was completed. During the periods as to which D&T has served as the Fund's independent registered public accounting firm, including the Fund's two most recent fiscal years preceding the fiscal year ended December 31, 2017, D&T's reports on the Fund's financial statements have not contained an adverse opinion or disclaimer of opinion and have not been qualified or modified as to uncertainty, audit scope or accounting principles. Further, there have been no disagreements with D&T on any matter of accounting principles or practices, financial statement disclosure, or auditing scope or procedure, which, if not resolved to the satisfaction of D&T, would have caused D&T to make reference to the subject matter of the disagreement in connection with its report on the financial statements. In addition, there have been no reportable events of the kind described in Item 304(a)(1)(v) of Regulation S-K under the Securities Exchange Act of 1934. Effective immediately following the completion of the Transaction on July 3, 2017, the Board, acting upon the recommendation of the Audit Committee, engaged a new independent registered public accounting firm, Ernst & Young LLP ("EY"), for the Fund's fiscal year ended December 31, 2017. Prior to its engagement, EY had advised the Fund's Audit Committee that EY had identified the following matters, in each case relating to services rendered by other member firms of Ernst & Young Global Limited, all of which are located outside the United States, to UniCredit and certain of its subsidiaries during the period commencing July 1, 2016, that it determined to be inconsistent with the auditor independence rules set forth by the Securities 38 Pioneer Core Equity Fund | Semiannual Report | 6/30/17 and Exchange Commission ("SEC"): (a) project management support services to UniCredit in the Czech Republic, Germany, Italy, Serbia and Slovenia in relation to twenty-two projects, that were determined to be inconsistent with Rule 2-01(c)(4)(vi) of Regulation S-X (management functions); (b) two engagements for UniCredit in Italy where fees were contingent/success based and that were determined to be inconsistent with Rule 2-01(c)(5) of Regulation S-X (contingent fees); (c) four engagements where legal and expert services were provided to UniCredit in the Czech Republic and Germany, and twenty engagements where the legal advisory services were provided to UniCredit in Austria, Czech Republic, Italy and Poland, that were determined to be inconsistent with Rule 2-01(c)(4)(ix) and (x) of Regulation S-X (legal and expert services); and (d) two engagements for UniCredit in Italy involving assistance in the sale of certain assets, that were determined to be inconsistent with Rule 2-01(c)(4)(viii) of Regulation S-X (broker-dealer, investment advisor or investment banking services). None of the foregoing services involved the Fund, any of the other Funds in the Pioneer Family of Funds or any other Pioneer entity sold by UniCredit in the Transaction. EY advised the Audit Committee that it had considered the matters described above and had concluded that such matters would not impair EY's ability to exercise objective and impartial judgment in connection with the audits of the financial statements of the Fund under the SEC and Public Company Accounting Oversight Board independence rules, and that a reasonable investor with knowledge of all relevant facts and circumstances would reach the same conclusion. Management and the Audit Committee considered these matters and discussed the matters with EY and, based upon EY's description of the matters and statements made by EY, Management and the Audit Committee believe that EY will be capable of exercising objective and impartial judgment in connection with the audits of the financial statements of the Fund, and Management further believes that a reasonable investor with knowledge of all relevant facts and circumstances would reach the same conclusion. Pioneer Core Equity Fund | Semiannual Report | 6/30/17 39 Approval of New and Interim Management Agreements Amundi Pioneer Asset Management, Inc. (Amundi Pioneer), formerly Pioneer Investment Management, Inc. (PIM), serves as the investment adviser to Pioneer Core Equity Fund (the Fund) pursuant to an investment management agreement between Amundi Pioneer and the Fund. On July 3, 2017, Amundi acquired Pioneer Investments, a group of asset management companies located throughout the world (the "Transaction"). As a result of the Transaction, Amundi Pioneer became an indirect wholly-owned subsidiary of Amundi and Amundi's wholly-owned subsidiary, Amundi USA, Inc. Prior to July 3, 2017, Pioneer Investments was owned by Pioneer Global Asset Management S.p.A. ("PGAM"), a wholly-owned subsidiary of UniCredit S.p.A. ("UniCredit"). Under the Investment Company Act of 1940, the Fund's investment management agreement with PIM (the "Current Management Agreement") terminated automatically upon the consummation of the Transaction. In order for Amundi Pioneer to continue to manage the Fund after the consummation of the Transaction, the Trustees and shareholders of the Fund were required to approve a new investment management agreement for the Fund (the "New Management Agreement"). As discussed below, the Board of Trustees of the Fund approved the New Management Agreement at a meeting held on March 6-7, 2017. The New Management Agreement was approved by the shareholders of the Fund at a meeting held on June 13, 2017. The Board of Trustees of the Fund also approved an interim investment management agreement between Amundi Pioneer and the Fund (the "Interim Management Agreement") at the March 6-7, 2017 meeting. The Interim Management Agreement would have taken effect upon the closing of the Transaction in the event that the shareholders of the Fund did not approve the New Management Agreement. Board Evaluation of the New and Interim Management Agreements The Board evaluated the Transaction and the New Management Agreement and Interim Management Agreement for the Fund. In connection with their evaluation of the Transaction and the New Management Agreement for the Fund, the Trustees requested such information as they deemed reasonably necessary, including: (a) the structure of the Transaction and the strategy underlying the Transaction; (b) the anticipated benefits of the Transaction to the Fund and its shareholders; (c) the post-Transaction plans for Amundi Pioneer, including Amundi's plans for integration of Pioneer Investments and Amundi Pioneer with its existing asset management businesses and plans for the future development of Amundi Pioneer; (d) the effect of the Transaction on the ongoing services provided to the Fund, including the need to select a new independent registered public accounting firm for the Fund, and any plans to modify the operations of the Fund; (e) the stability and continuity of Amundi Pioneer's management and 40 Pioneer Core Equity Fund | Semiannual Report | 6/30/17 key employees, including compensation and benefits to Amundi Pioneer's key employees, and retention plans and incentive plan structure; (f) the post- Transaction indebtedness and financial resources of Amundi Pioneer; (g) Amundi's legal and operational structure, its principal shareholders and senior management, its investment management, risk management, administrative, legal and compliance functions; (h) certain regulatory matters relating to Amundi's affiliates; and (i) Amundi's commitment to the United States, including the role of Amundi Pioneer in the larger Amundi business. The Trustees also requested and obtained the following information in connection with their evaluation of the Transaction and the New Management Agreement for the Fund: (i) memoranda provided by Fund counsel that summarized the legal standards and other considerations that are relevant to the Trustees in their deliberations regarding the New Management Agreement; (ii) the qualifications of the investment management teams for the Fund, as well as the level of investment by the Fund's portfolio managers in the Fund; (iii) the Fund's management fees and total expense ratios, the financial statements of Amundi Pioneer and its pre- and post-Transaction parent companies, profitability analyses from Amundi Pioneer, and analyses from Amundi Pioneer as to possible economies of scale; (iv) the profitability of the institutional business of Amundi Pioneer and Amundi Pioneer's affiliate, Amundi Pioneer Institutional Asset Management, Inc. ("Amundi Pioneer Institutional") as compared to that of Amundi Pioneer's fund management business; and (v) the differences between the fees and expenses of the Fund and the fees and expenses of Amundi Pioneer's and Amundi Pioneer Institutional's institutional accounts, as well as the different services provided by Adviser to the Fund and by Amundi Pioneer and Amundi Pioneer Institutional to the institutional accounts. In addition, the Trustees considered the information provided at regularly scheduled meetings throughout the year regarding the Fund's performance and risk attributes, including through meetings with investment management personnel, and took into account other information related to the Fund provided to the Trustees at regularly scheduled meetings. The Trustees also considered information they had received in their review of the continuance of the Current Management Agreement for the Fund in September 2016. At meetings held on January 9, 2017 and January 10, 2017, the Trustees met with representatives of Amundi and PGAM, including separate meetings of the Trustees who are not "interested persons" of the Fund Complex ("Independent Trustees") and counsel with representatives of Amundi and PGAM, and subsequently with representatives of Amundi. In those meetings, they received an extensive presentation from the representatives of Amundi, including the chief executive officer of Amundi, describing Amundi's background and history, its global asset management activities, the growth of its business, and its status as the largest asset management firm in Europe and one of the largest globally; its capital structure and financial resources, including information as to the financing of the Pioneer Core Equity Fund | Semiannual Report | 6/30/17 41 Transaction; its principal investors, including its majority investor Credit Agricole S.A., and Credit Agricole's long-term commitment to the asset management business; the philosophy and strategy underlying the Transaction and the complementarity of Amundi's and Pioneer Investments' respective asset management businesses; Amundi's various operating and investment committees and how they would likely interact with Amundi Pioneer; the proposed integration process, including the progress to date and the establishment of various integration work streams; Amundi's plans for management of Amundi Pioneer; Amundi's philosophy as to compensation of key employees and its general intentions with respect to incentive plans for key employees of Amundi Pioneer; Amundi's preliminary plans to achieve cost and other synergies; and opportunities to further develop the business of Amundi Pioneer and Amundi Pioneer Institutional, including in the area of institutional asset management, and how that would benefit shareholders of the Pioneer Funds. In those meetings, the representatives of Amundi confirmed their intention that the Chief Executive Officer and Chief Investment Officer of Amundi Pioneer would remain in their current positions, and confirmed that they do not currently foresee major changes in the day-to-day investment management operations of Amundi Pioneer with respect to the Fund as a direct result of the Transaction. They discussed incentive arrangements for key personnel that would continue after the closing of the Transaction and their plans to establish a new long-term incentive plan following the closing. They also generally discussed ways in which Amundi Pioneer could potentially draw on the expanded global resources of Amundi post-Transaction. At those meetings, the Independent Trustees identified certain areas to which they requested further information, including as to trading and execution of securities transactions, research and portfolio management and potential changes in investment process, particularly where asset classes managed by Amundi Pioneer would overlap with asset classes managed by Amundi, the continued availability of resources currently at Pioneer Investments or elsewhere within Amundi to assist in management of certain Funds, and any anticipated significant changes in operations. The Independent Trustees considered the uncertainty as to whether the Fund's independent registered public accounting firm could continue to act in that capacity after the closing of the Transaction. The Independent Trustees also met with counsel to review the information they had received to date and to discuss next steps. Subsequently, the Trustees received further information from Amundi, including written responses to questions raised by the Independent Trustees, and received from Amundi Pioneer the information requested of it. The Independent Trustees reviewed the information provided with counsel at telephonic meetings held on February 16, 2017 and February 27, 2017. The Trustees held a special in-person Board meeting on March 6-7, 2017 for further consideration of the New Management Agreements, the Interim Management Agreements and the Transaction. The Trustees met again with senior executives of Amundi at the March 6-7, 2017 meeting. 42 Pioneer Core Equity Fund | Semiannual Report | 6/30/17 At the March 6-7, 2017 meeting, based on their evaluation of the information provided by Amundi Pioneer and Amundi, the Trustees including the Independent Trustees voting separately, approved the New Management Agreement and the Interim Management Agreement for the Fund. In considering the New Management Agreement for the Fund, the Trustees considered various factors that they determined were relevant, including the factors described below. The Trustees did not identify any single factor as the controlling factor in their determinations. The Trustees considered the same factors with respect to the Interim Management Agreement for the Fund. Nature, Extent and Quality of Services The Trustees considered the nature, extent and quality of the services that had been provided by Amundi Pioneer to the Fund and that are expected to be provided by Amundi Pioneer to the Fund following the consummation of the Transaction. The Trustees reviewed the terms of the New Management Agreement, and noted that such terms are substantially similar to the terms of the Current Management Agreement, except for different execution dates, effective dates and termination dates. The Trustees reviewed Amundi Pioneer's investment approach for the Fund and its research process. The Trustees considered the resources of Amundi Pioneer and the personnel of Amundi Pioneer who provide investment management services to the Fund. They also reviewed the amount of non-investment resources and personnel of Amundi Pioneer that are involved in Amundi Pioneer's services to the Fund, including Amundi Pioneer's compliance and legal resources and personnel. The Trustees noted the substantial attention and high priority given by Amundi Pioneer's senior management to the Pioneer Fund complex. The Trustees considered that Amundi Pioneer supervises and monitors the performance of the Fund's service providers and provides the Fund with personnel (including Fund officers) and other resources that are necessary for the Fund's business management and operations and that Amundi Pioneer would continue to provide those investment management and research services and resources to the Fund following the consummation of the Transaction. The Trustees also considered that, as administrator, Amundi Pioneer would continue to be responsible for the administration of the Fund's business and other affairs. The Trustees considered the fees to be paid to Amundi Pioneer for the provision of administration services. The Trustees considered that Deloitte & Touche LLP informed the Board that it would no longer be independent with respect to the Fund upon the completion of the Transaction and, accordingly, that it would be necessary for the Board to engage a new independent registered public accounting firm for the Fund. Pioneer Core Equity Fund | Semiannual Report | 6/30/17 43 The Trustees considered that the Transaction was not expected to have a material adverse impact on the nature, scope and overall quality of services provided to the Fund and its shareholders, including investment management, risk management, administrative, compliance, legal and other services, as a result of the Transaction. In that regard, the Trustees considered that Amundi is one of the largest asset managers globally, and that Amundi Pioneer may have access to additional research and portfolio management capabilities as a result of the Transaction and that Amundi Pioneer, as part of Amundi, is expected to have an enhanced global presence that may contribute to an increase in the overall scale and resources of Amundi Pioneer. Furthermore, in considering whether the Transaction would be expected to have a material adverse impact on the nature, scope and overall quality of services provided to the Fund and its shareholders, the Trustees considered the statements by representatives of Amundi that they expect the Chief Executive Officer and Chief Investment Officer of Amundi Pioneer to remain in their current positions and that they do not currently foresee major changes in the day-to-day investment management operations of Amundi Pioneer as a direct result of the Transaction, or the risk management, legal or compliance services provided by Amundi Pioneer, with respect to the Fund. They further considered the current incentive arrangements for key personnel of Amundi Pioneer that would continue after the closing of the Transaction. They also noted Amundi's stated intention to establish a new long-term incentive plan following the closing. The Trustees also took into account their experience in evaluating the proposed combination of Pioneer Investments and Santander Asset Management, which was announced in September, 2014 and abandoned in July, 2016. In light of, among other things, this experience, the Trustees determined that they were not able to identify any realistic alternatives to approving the New Management Agreement that would provide the level of services to the Fund and its shareholders that are expected to be provided by Amundi Pioneer after the closing of the Transaction. Based on these considerations, the Trustees concluded that the nature, extent and quality of services that Amundi Pioneer would continue to provide to the Fund under the New Management Agreement would be satisfactory and consistent with the terms of the New Management Agreement. Performance of the Fund In considering the Fund's performance, the Trustees regularly reviewed and discussed throughout the year data prepared by Amundi Pioneer and information comparing the Fund's performance with the performance of its peer group of funds, as classified by each of Morningstar, Inc. (Morningstar) and Lipper, and the performance of the Fund's benchmark index. They also discussed the Fund's performance with Amundi Pioneer on a regular basis. 44 Pioneer Core Equity Fund | Semiannual Report | 6/30/17 The Trustees discussed the Fund's performance with Amundi Pioneer on a more frequent basis in light of the Fund's unfavorable performance compared to its benchmark index and peers over certain periods. The Trustees noted Amundi Pioneer's explanation for the Fund's relative performance and the steps taken by Amundi Pioneer to address the Fund's performance, including enhancing the investment process used for the Fund. It also was noted that Craig Sterling, a Senior Vice President and Head of Equity Research, U.S., became a portfolio manager of the Fund in May, 2015. The Trustees' regular reviews and discussions, including the steps taken by Amundi Pioneer to address the Fund's performance, were factored into the Trustees' deliberations concerning the approval of the New Management Agreement. Management Fee and Expenses The Trustees noted that the stated management fees to be paid by the Fund are identical under the Current Management Agreement and the New Management Agreement. The Trustees considered information showing the fees and expenses of the Fund in comparison to the management fees and expense ratios of its peer group of funds as classified by Morningstar and also to the expense ratios of a peer group of funds selected on the basis of criteria determined by the Independent Trustees for this purpose using data provided by Strategic Insight Mutual Fund Research and Consulting, LLC (Strategic Insight), an independent third party. In all quintile rankings referred to below, first quintile is most favorable to the Fund's shareowners. To the extent applicable, the Trustees also considered the impact of transfer agency, sub-transfer agency, and other non- management fee expenses on the expense ratios of the Fund. The Trustees noted that they separately review the Fund's transfer agency, sub-transfer agency and intermediary arrangements and that the results of the most recent such review were considered in the consideration of the Fund's expense ratio. The Trustees considered that the Fund's management fee as of September 30, 2016 was in the first quintile relative to the management fees paid by other funds in its Morningstar category for the comparable period. The Trustees considered that the expense ratio of the Fund's Class A shares as of September 30, 2016 was in the first quintile relative to its Morningstar category and in the first quintile relative to its Strategic Insight peer group, in each case for the comparable period. The Trustees reviewed management fees charged by Amundi Pioneer and Amundi Pioneer Institutional to institutional and other clients, including publicly offered European funds sponsored by Amundi Pioneer's affiliates, unaffiliated U.S. registered investment companies (in a sub-advisory capacity), and unaffiliated foreign and domestic separate accounts. The Trustees also considered Amundi Pioneer's costs in providing services to the Fund and Amundi Pioneer's and Amundi Pioneer Institutional's costs in providing services to the other clients and considered the differences in management fees and profit margins for fund and Pioneer Core Equity Fund | Semiannual Report | 6/30/17 45 non-fund services. In evaluating the fees associated with Amundi Pioneer's and Amundi Pioneer Institutional's client accounts, the Trustees took into account the respective demands, resources and complexity associated with the Fund and other client accounts. The Trustees noted that in some instances the fee rates for those clients were lower than the management fee for the Fund and considered that, under both the Current Management Agreement and the New Management Agreement, Amundi Pioneer would perform additional services for the Fund that it does not provide to those other clients or services that are broader in scope, including oversight of the Fund's other service providers and activities related to compliance and the extensive regulatory and tax regimes to which the Fund is subject. The Trustees also considered the different risks associated with Amundi Pioneer's management of the Fund and Amundi Pioneer's and Amundi Pioneer Institutional's management of the other client accounts. The Trustees concluded that the management fee payable by the Fund to Amundi Pioneer was reasonable in relation to the nature and quality of the services to be provided by Amundi Pioneer. Profitability The Trustees considered information provided by Amundi Pioneer regarding the profitability of Amundi Pioneer with respect to the advisory services provided by Amundi Pioneer to the Fund, including the methodology used by Amundi Pioneer in allocating certain of its costs to the management of the Fund. The Trustees also considered Amundi Pioneer's profit margin in connection with the overall operation of the Fund. They further reviewed the financial results, including the profit margins, realized by Amundi Pioneer and Amundi Pioneer Institutional from non-fund businesses. The Trustees considered Amundi Pioneer's profit margins with respect to the Fund in comparison to the limited industry data available and noted that the profitability of any adviser was affected by numerous factors, including its organizational structure and method for allocating expenses. The Trustees concluded that Amundi Pioneer's profitability with respect to the management of the Fund was not unreasonable. Economies of Scale The Trustees considered Amundi Pioneer's views relating to economies of scale in connection with the Pioneer Funds as fund assets grow and the extent to which any such economies of scale are shared with the Fund and Fund shareholders. The Trustees recognize that economies of scale are difficult to identify and quantify, and that, among other factors that may be relevant, are the following: fee levels, expense subsidization, investment by Amundi Pioneer in research and analytical capabilities and Amundi Pioneer's commitment and resource allocation to the Fund. The Trustees noted that profitability also may be an indicator of the availability of any economies of scale, although profitability may vary for other reasons including due to reductions in expenses. The Trustees concluded that economies of scale, if any, were being appropriately shared with the Fund. 46 Pioneer Core Equity Fund | Semiannual Report | 6/30/17 Other Benefits The Trustees considered the other benefits that Amundi Pioneer enjoys from its relationship with the Fund. The Trustees considered the character and amount of fees paid or to be paid by the Fund, other than under the Current Management Agreement or the New Management Agreement, for services provided by Amundi Pioneer and its affiliates. The Trustees further considered the revenues and profitability of Amundi Pioneer's businesses other than the Fund business. To the extent applicable, the Trustees also considered the benefits to the Fund and to Amundi Pioneer and its affiliates from the use of "soft" commission dollars generated by the Fund to pay for research and brokerage services. The Trustees considered that following the completion of the Transaction, Amundi Pioneer will be the principal U.S. asset management business of Amundi, and that Amundi's worldwide asset management business will manage over $1.38 trillion in assets (including the Pioneer Funds). This may create opportunities for Amundi Pioneer, Amundi Pioneer Institutional and Amundi that derive from Amundi Pioneer's relationships with the Fund, including Amundi's ability to market the services of Amundi Pioneer globally. The Trustees noted that Amundi Pioneer may have access to additional research capabilities as a result of the Transaction and Amundi's enhanced global presence that may contribute to an increase of the overall scale of Amundi Pioneer. The Trustees considered that Amundi Pioneer and the Fund are expected to receive reciprocal intangible benefits from the relationship, including mutual brand recognition and, for the Fund, direct and indirect access to the resources of a large global asset manager. The Trustees concluded that any such benefits received by Amundi Pioneer as a result of its relationship with the Fund were reasonable. Conclusion After consideration of the factors described above as well as other factors, the Trustees, including the Independent Trustees, concluded that the New Management Agreement and the Interim Management Agreement for the Fund, including the fees payable thereunder, were fair and reasonable and voted to approve the New Management Agreement and the Interim Management Agreement, and to recommend that shareholders approve the New Management Agreement. Pioneer Core Equity Fund | Semiannual Report | 6/30/17 47 Trustees, Officers and Service Providers Trustees Officers Thomas J. Perna, Chairman Lisa M. Jones, President and Chief David R. Bock Executive Officer Benjamin M. Friedman Mark E. Bradley, Treasurer and Margaret B.W. Graham Chief Financial Officer Lisa M. Jones Christopher J. Kelley, Secretary and Lorraine H. Monchak Chief Legal Officer Marguerite A. Piret Fred J. Ricciardi Kenneth J. Taubes Investment Adviser and Administrator Amundi Pioneer Asset Management, Inc., formerly Pioneer Investment Management, Inc. Custodian and Sub-Administrator Brown Brothers Harriman & Co. Principal Underwriter Amundi Pioneer Distributor, Inc., formerly Pioneer Funds Distributor, Inc. Legal Counsel Morgan, Lewis & Bockius LLP Shareowner Services and Transfer Agent Boston Financial Data Services, Inc. Proxy Voting Policies and Procedures of the Fund are available without charge, upon request, by calling our toll free number (1-800-225-6292). Information regarding how the Fund voted proxies relating to portfolio securities during the most recent 12-month period ended June 30 is publicly available to shareowners at www.amundipioneer.com. This information is also available on the Securities and Exchange Commission's web site at www.sec.gov. 48 Pioneer Core Equity Fund | Semiannual Report | 6/30/17 This page is for your notes. Pioneer Core Equity Fund | Semiannual Report | 6/30/17 49 This page is for your notes. 50 Pioneer Core Equity Fund | Semiannual Report | 6/30/17 This page is for your notes. Pioneer Core Equity Fund | Semiannual Report | 6/30/17 51 This page is for your notes. 52 Pioneer Core Equity Fund | Semiannual Report | 6/30/17 How to Contact Amundi Pioneer We are pleased to offer a variety of convenient ways for you to contact us for assistance or information. Call us for: -------------------------------------------------------------------------------- Account Information, including existing accounts, new accounts, prospectuses, applications and service forms 1-800-225-6292 FactFone(SM) for automated fund yields, prices, account information and transactions 1-800-225-4321 Retirement plans information 1-800-622-0176 Write to us: -------------------------------------------------------------------------------- Amundi Pioneer P.O. Box 55014 Boston, Massachusetts 02205-5014 Our toll-free fax 1-800-225-4240 Our internet e-mail address ask.amundipioneer@amundipioneer.com (for general questions about Amundi Pioneer only) Visit our web site: www.amundipioneer.com This report must be preceded or accompanied by a prospectus. The Fund files a complete schedule of investments with the Securities and Exchange Commission for the first and third quarters for each fiscal year on Form N-Q. Shareholders may view the filed Form N-Q by visiting the Commission's web site at http://www.sec.gov. The filed form may also be viewed and copied at the Commission's Public Reference Room in Washington, DC. Information regarding the operations of the Public Reference Room may be obtained by calling 1-800-SEC-0330. [LOGO] Amundi Pioneer ============== ASSET MANAGEMENT Amundi Pioneer Asset Management, Inc. 60 State Street Boston, MA 02109 www.amundipioneer.com Securities offered through Amundi Pioneer Distributor, Inc. 60 State Street, Boston, MA 02109 Underwriter of Pioneer Mutual Funds, Member SIPC (C) 2017 Amundi Pioneer Asset Management 19408-11-0817 ITEM 2. CODE OF ETHICS. (a) Disclose whether, as of the end of the period covered by the report, the registrant has adopted a code of ethics that applies to the registrant's principal executive officer, principal financial officer, principal accounting officer or controller, or persons performing similar functions, regardless of whether these individuals are employed by the registrant or a third party. If the registrant has not adopted such a code of ethics, explain why it has not done so. The registrant has adopted, as of the end of the period covered by this report, a code of ethics that applies to the registrant's principal executive officer, principal financial officer, principal accounting officer and controller. (b) For purposes of this Item, the term "code of ethics" means written standards that are reasonably designed to deter wrongdoing and to promote: (1) Honest and ethical conduct, including the ethical handling of actual or apparent conflicts of interest between personal and professional relationships; (2) Full, fair, accurate, timely, and understandable disclosure in reports and documents that a registrant files with, or submits to, the Commission and in other public communications made by the registrant; (3) Compliance with applicable governmental laws, rules, and regulations; (4) The prompt internal reporting of violations of the code to an appropriate person or persons identified in the code; and (5) Accountability for adherence to the code. (c) The registrant must briefly describe the nature of any amendment, during the period covered by the report, to a provision of its code of ethics that applies to the registrant's principal executive officer, principal financial officer, principal accounting officer or controller, or persons performing similar functions, regardless of whether these individuals are employed by the registrant or a third party, and that relates to any element of the code of ethics definition enumerated in paragraph (b) of this Item. The registrant must file a copy of any such amendment as an exhibit pursuant to Item 10(a), unless the registrant has elected to satisfy paragraph (f) of this Item by posting its code of ethics on its website pursuant to paragraph (f)(2) of this Item, or by undertaking to provide its code of ethics to any person without charge, upon request, pursuant to paragraph (f)(3) of this Item. The registrant has made no amendments to the code of ethics during the period covered by this report. (d) If the registrant has, during the period covered by the report, granted a waiver, including an implicit waiver, from a provision of the code of ethics to the registrant's principal executive officer, principal financial officer, principal accounting officer or controller, or persons performing similar functions, regardless of whether these individuals are employed by the registrant or a third party, that relates to one or more of the items set forth in paragraph (b) of this Item, the registrant must briefly describe the nature of the waiver, the name of the person to whom the waiver was granted, and the date of the waiver. Not applicable. (e) If the registrant intends to satisfy the disclosure requirement under paragraph (c) or (d) of this Item regarding an amendment to, or a waiver from, a provision of its code of ethics that applies to the registrant's principal executive officer, principal financial officer, principal accounting officer or controller, or persons performing similar functions and that relates to any element of the code of ethics definition enumerated in paragraph (b) of this Item by posting such information on its Internet website, disclose the registrant's Internet address and such intention. Not applicable. (f) The registrant must: (1) File with the Commission, pursuant to Item 12(a)(1), a copy of its code of ethics that applies to the registrant's principal executive officer,principal financial officer, principal accounting officer or controller, or persons performing similar functions, as an exhibit to its annual report on this Form N-CSR (see attachment); (2) Post the text of such code of ethics on its Internet website and disclose, in its most recent report on this Form N-CSR, its Internet address and the fact that it has posted such code of ethics on its Internet website; or (3) Undertake in its most recent report on this Form N-CSR to provide to any person without charge, upon request, a copy of such code of ethics and explain the manner in which such request may be made. 	See Item 10(2) ITEM 3. AUDIT COMMITTEE FINANCIAL EXPERT. (a) (1) Disclose that the registrant's board of trustees has determined that the registrant either: (i) Has at least one audit committee financial expert serving on its audit committee; or (ii) Does not have an audit committee financial expert serving on its audit committee. The registrant's Board of Trustees has determined that the registrant has at least one audit committee financial expert. (2) If the registrant provides the disclosure required by paragraph (a)(1)(i) of this Item, it must disclose the name of the audit committee financial expert and whether that person is "independent." In order to be considered "independent" for purposes of this Item, a member of an audit committee may not, other than in his or her capacity as a member of the audit committee, the board of trustees, or any other board committee: (i) Accept directly or indirectly any consulting, advisory, or other compensatory fee from the issuer; or (ii) Be an "interested person" of the investment company as defined in Section 2(a)(19) of the Act (15 U.S.C. 80a-2(a)(19)). Ms. Marguerite A. Piret, an independent trustee, is such an audit committee financial expert. (3) If the registrant provides the disclosure required by paragraph (a)(1) (ii) of this Item, it must explain why it does not have an audit committee financial expert. Not applicable. ITEM 4. PRINCIPAL ACCOUNTANT FEES AND SERVICES. (a) Disclose, under the caption AUDIT FEES, the aggregate fees billed for each of the last two fiscal years for professional services rendered by the principal accountant for the audit of the registrant's annual financial statements or services that are normally provided by the accountant in connection with statutory and regulatory filings or engagements for those fiscal years. N/A (b) Disclose, under the caption AUDIT-RELATED FEES, the aggregate fees billed in each of the last two fiscal years for assurance and related services by the principal accountant that are reasonably related to the performance of the audit of the registrant's financial statements and are not reported under paragraph (a) of this Item. Registrants shall describe the nature of the services comprising the fees disclosed under this category. N/A (c) Disclose, under the caption TAX FEES, the aggregate fees billed in each of the last two fiscal years for professional services rendered by the principal accountant for tax compliance, tax advice, and tax planning. Registrants shall describe the nature of the services comprising the fees disclosed under this category. N/A (d) Disclose, under the caption ALL OTHER FEES, the aggregate fees billed in each of the last two fiscal years for products and services provided by the principal accountant, other than the services reported in paragraphs (a) through (c) of this Item. Registrants shall describe the nature of the services comprising the fees disclosed under this category. N/A (e) (1) Disclose the audit committee's pre-approval policies and procedures described in paragraph (c)(7) of Rule 2-01 of Regulation S-X. PIONEER FUNDS APPROVAL OF AUDIT, AUDIT-RELATED, TAX AND OTHER SERVICES PROVIDED BY THE INDEPENDENT AUDITOR SECTION I - POLICY PURPOSE AND APPLICABILITY The Pioneer Funds recognize the importance of maintaining the independence of their outside auditors. Maintaining independence is a shared responsibility involving Pioneer Investment Management, Inc ("PIM"), the audit committee and the independent auditors. The Funds recognize that a Fund's independent auditors: 1) possess knowledge of the Funds, 2) are able to incorporate certain services into the scope of the audit, thereby avoiding redundant work, cost and disruption of Fund personnel and processes, and 3) have expertise that has value to the Funds. As a result, there are situations where it is desirable to use the Fund's independent auditors for services in addition to the annual audit and where the potential for conflicts of interests are minimal. Consequently, this policy, which is intended to comply with Rule 210.2-01(C)(7), sets forth guidelines and procedures to be followed by the Funds when retaining the independent audit firm to perform audit, audit-related tax and other services under those circumstances, while also maintaining independence. Approval of a service in accordance with this policy for a Fund shall also constitute approval for any other Fund whose pre-approval is required pursuant to Rule 210.2-01(c)(7)(ii). In addition to the procedures set forth in this policy, any non-audit services that may be provided consistently with Rule 210.2-01 may be approved by the Audit Committee itself and any pre-approval that may be waived in accordance with Rule 210.2-01(c)(7)(i)(C) is hereby waived. Selection of a Fund's independent auditors and their compensation shall be determined by the Audit Committee and shall not be subject to this policy. SECTION II - POLICY ---------------- -------------------------------- ------------------------------------------------- SERVICE SERVICE CATEGORY DESCRIPTION SPECIFIC PRE-APPROVED SERVICE SUBCATEGORIES CATEGORY ---------------- -------------------------------- ------------------------------------------------- I. AUDIT Services that are directly o Accounting research assistance SERVICES related to performing the o SEC consultation, registration independent audit of the Funds statements, and reporting o Tax accrual related matters o Implementation of new accounting standards o Compliance letters (e.g. rating agency letters) o Regulatory reviews and assistance regarding financial matters o Semi-annual reviews (if requested) o Comfort letters for closed end offerings ---------------- -------------------------------- ------------------------------------------------- II. Services which are not o AICPA attest and agreed-upon procedures AUDIT-RELATED prohibited under Rule o Technology control assessments SERVICES 210.2-01(C)(4) (the "Rule") o Financial reporting control assessments and are related extensions of o Enterprise security architecture the audit services support the assessment audit, or use the knowledge/expertise gained from the audit procedures as a foundation to complete the project. In most cases, if the Audit-Related Services are not performed by the Audit firm, the scope of the Audit Services would likely increase. The Services are typically well-defined and governed by accounting professional standards (AICPA, SEC, etc.) ---------------- -------------------------------- ------------------------------------------------- ------------------------------------- ------------------------------------ AUDIT COMMITTEE APPROVAL POLICY AUDIT COMMITTEE REPORTING POLICY ------------------------------------- ------------------------------------ o "One-time" pre-approval o A summary of all such for the audit period for all services and related fees pre-approved specific service reported at each regularly subcategories. Approval of the scheduled Audit Committee independent auditors as meeting. auditors for a Fund shall constitute pre approval for these services. ------------------------------------- ------------------------------------ o "One-time" pre-approval o A summary of all such for the fund fiscal year within services and related fees a specified dollar limit (including comparison to for all pre-approved specified dollar limits) specific service subcategories reported quarterly. o Specific approval is needed to exceed the pre-approved dollar limit for these services (see general Audit Committee approval policy below for details on obtaining specific approvals) o Specific approval is needed to use the Fund's auditors for Audit-Related Services not denoted as "pre-approved", or to add a specific service subcategory as "pre-approved" ------------------------------------- ------------------------------------ SECTION III - POLICY DETAIL, CONTINUED ----------------------- --------------------------- ----------------------------------------------- SERVICE CATEGORY SERVICE CATEGORY SPECIFIC PRE-APPROVED SERVICE SUBCATEGORIES DESCRIPTION ----------------------- --------------------------- ----------------------------------------------- III. TAX SERVICES Services which are not o Tax planning and support prohibited by the Rule, o Tax controversy assistance if an officer of the Fund o Tax compliance, tax returns, excise determines that using the tax returns and support Fund's auditor to provide o Tax opinions these services creates significant synergy in the form of efficiency, minimized disruption, or the ability to maintain a desired level of confidentiality. ----------------------- --------------------------- ----------------------------------------------- ------------------------------------- ------------------------- AUDIT COMMITTEE APPROVAL POLICY AUDIT COMMITTEE REPORTING POLICY ------------------------------------- ------------------------- ------------------------------------- ------------------------- o "One-time" pre-approval o A summary of for the fund fiscal year all such services and within a specified dollar limit related fees 				 (including comparison 			 to specified dollar 			 limits) reported 			 quarterly. o Specific approval is needed to exceed the pre-approved dollar limits for these services (see general Audit Committee approval policy below for details on obtaining specific approvals) o Specific approval is needed to use the Fund's auditors for tax services not denoted as pre-approved, or to add a specific service subcategory as "pre-approved" ------------------------------------- ------------------------- SECTION III - POLICY DETAIL, CONTINUED ----------------------- --------------------------- ----------------------------------------------- SERVICE CATEGORY SERVICE CATEGORY SPECIFIC PRE-APPROVED SERVICE SUBCATEGORIES DESCRIPTION ----------------------- --------------------------- ----------------------------------------------- IV. OTHER SERVICES Services which are not o Business Risk Management support prohibited by the Rule, o Other control and regulatory A. SYNERGISTIC, if an officer of the Fund compliance projects UNIQUE QUALIFICATIONS determines that using the Fund's auditor to provide these services creates significant synergy in the form of efficiency, minimized disruption, the ability to maintain a desired level of confidentiality, or where the Fund's auditors posses unique or superior qualifications to provide these services, resulting in superior value and results for the Fund. ----------------------- --------------------------- ----------------------------------------------- --------------------------------------- ------------------------ AUDIT COMMITTEE APPROVAL POLICY AUDIT COMMITTEE REPORTING POLICY ------------------------------------- -------------------------- o "One-time" pre-approval o A summary of for the fund fiscal year within all such services and a specified dollar limit related fees 			 (including comparison 			 to specified dollar 				 limits) reported quarterly. o Specific approval is needed to exceed the pre-approved dollar limits for these services (see general Audit Committee approval policy below for details on obtaining specific approvals) o Specific approval is needed to use the Fund's auditors for "Synergistic" or "Unique Qualifications" Other Services not denoted as pre-approved to the left, or to add a specific service subcategory as "pre-approved" ------------------------------------- -------------------------- SECTION III - POLICY DETAIL, CONTINUED ----------------------- ------------------------- ----------------------------------------------- SERVICE CATEGORY SERVICE CATEGORY SPECIFIC PROHIBITED SERVICE SUBCATEGORIES DESCRIPTION ----------------------- ------------------------- ----------------------------------------------- PROHIBITED SERVICES Services which result 1. Bookkeeping or other services in the auditors losing related to the accounting records or independence status financial statements of the audit under the Rule. client* 2. Financial information systems design and implementation* 3. Appraisal or valuation services, fairness* opinions, or contribution-in-kind reports 4. Actuarial services (i.e., setting actuarial reserves versus actuarial audit work)* 5. Internal audit outsourcing services* 6. Management functions or human resources 7. Broker or dealer, investment advisor, or investment banking services 8. Legal services and expert services unrelated to the audit 9. Any other service that the Public Company Accounting Oversight Board determines, by regulation, is impermissible ----------------------- ------------------------- ----------------------------------------------- ------------------------------------------- ------------------------------ AUDIT COMMITTEE APPROVAL POLICY AUDIT COMMITTEE REPORTING POLICY ------------------------------------------- ------------------------------ o These services are not to be o A summary of all performed with the exception of the(*) services and related services that may be permitted fees reported at each if they would not be subject to audit regularly scheduled procedures at the audit client (as Audit Committee meeting defined in rule 2-01(f)(4)) level will serve as continual the firm providing the service. confirmation that has 				 not provided any restricted services. ------------------------------------------- ------------------------------ -------------------------------------------------------------------------------- GENERAL AUDIT COMMITTEE APPROVAL POLICY: o For all projects, the officers of the Funds and the Fund's auditors will each make an assessment to determine that any proposed projects will not impair independence. o Potential services will be classified into the four non-restricted service categories and the "Approval of Audit, Audit-Related, Tax and Other Services" Policy above will be applied. Any services outside the specific pre-approved service subcategories set forth above must be specifically approved by the Audit Committee. o At least quarterly, the Audit Committee shall review a report summarizing the services by service category, including fees, provided by the Audit firm as set forth in the above policy. -------------------------------------------------------------------------------- (2) Disclose the percentage of services described in each of paragraphs (b) through (d) of this Item that were approved by the audit committee pursuant to paragraph (c)(7)(i)(C) of Rule 2-01 of Regulation S-X. N/A (f) If greater than 50 percent, disclose the percentage of hours expended on the principal accountants engagement to audit the registrant's financial statements for the most recent fiscal year that were attributed to work performed by persons other than the principal accountant's full-time, permanent employees. N/A (g) Disclose the aggregate non-audit fees billed by the registrants accountant for services rendered to the registrant, and rendered to the registrants investment adviser (not including any sub-adviser whose role is primarily portfolio management and is subcontracted with or overseen by another investment adviser), and any entity controlling, controlled by, or under common control with the adviser that provides ongoing services to the registrant for each of the last two fiscal years of the registrant. N/A (h) Disclose whether the registrants audit committee of the board of trustees has considered whether the provision of non-audit services that were rendered to the registrants investment adviser (not including any subadviser whose role is primarily portfolio management and is subcontracted with or overseen by another investment adviser), and any entity controlling, controlled by, or under common control with the investment adviser that provides ongoing services to the registrant that were not pre-approved pursuant to paragraph (c)(7)(ii) of Rule 2-01 of Regulation S-X is compatible with maintaining the principal accountant's independence. The Fund's audit committee of the Board of Trustees has considered whether the provision of non-audit services that were rendered to the Affiliates (as defined) that were not pre- approved pursuant to paragraph (c)(7)(ii) of Rule 2-01 of Regulation S-X is compatible with maintaining the principal accountant's independence. ITEM 5. AUDIT COMMITTEE OF LISTED REGISTRANTS (a) If the registrant is a listed issuer as defined in Rule 10A-3 under the Exchange Act (17 CFR 240.10A-3), state whether or not the registrant has a separately-designated standing audit committee established in accordance with Section 3(a)(58)(A) of the Exchange Act (15 U.S.C. 78c(a)(58)(A)). If the registrant has such a committee, however designated, identify each committee member. If the entire board of directors is acting as the registrant's audit committee as specified in Section 3(a)(58)(B) of the Exchange Act (15 U.S.C. 78c(a)(58)(B)), so state. N/A (b) If applicable, provide the disclosure required by Rule 10A-3(d) under the Exchange Act (17 CFR 240.10A-3(d)) regarding an exemption from the listing standards for audit committees. N/A ITEM 6. SCHEDULE OF INVESTMENTS. File Schedule of Investments in securities of unaffiliated issuers as of the close of the reporting period as set forth in 210.1212 of Regulation S-X [17 CFR 210.12-12], unless the schedule is included as part of the report to shareholders filed under Item 1 of this Form. Included in Item 1 ITEM 7. DISCLOSURE OF PROXY VOTING POLICIES AND PROCEDURES FOR CLOSED-END MANAGEMENT INVESTMENT COMPANIES. A closed-end management investment company that is filing an annual report on this Form N-CSR must, unless it invests exclusively in non-voting securities, describe the policies and procedures that it uses to determine how to vote proxies relating to portfolio securities, including the procedures that the company uses when a vote presents a conflict between the interests of its shareholders, on the one hand, and those of the company's investment adviser; principal underwriter; or any affiliated person (as defined in Section 2(a)(3) of the Investment Company Act of 1940 (15 U.S.C. 80a-2(a)(3)) and the rules thereunder) of the company, its investment adviser, or its principal underwriter, on the other. Include any policies and procedures of the company's investment adviser, or any other third party, that the company uses, or that are used on the company's behalf, to determine how to vote proxies relating to portfolio securities. Not applicable to open-end management investment companies. ITEM 8. PORTFOLIO MANAGERS OF CLOSED-END MANAGEMENT INVESTMENT COMPANIES. (a) If the registrant is a closed-end management investment company that is filing an annual report on this Form N-CSR,provide the following information: (1) State the name, title, and length of service of the person or persons employed by or associated with the registrant or an investment adviser of the registrant who are primarily responsible for the day-to-day management of the registrant's portfolio ("Portfolio Manager"). Also state each Portfolio Manager's business experience during the past 5 years. Not applicable to open-end management investment companies. ITEM 9. PURCHASES OF EQUITY SECURITIES BY CLOSED-END MANAGEMENT INVESTMENT COMPANY AND AFFILIATED PURCHASERS. (a) If the registrant is a closed-end management investment company, in the following tabular format, provide the information specified in paragraph (b) of this Item with respect to any purchase made by or on behalf of the registrant or any affiliated purchaser, as defined in Rule 10b-18(a)(3) under the Exchange Act (17 CFR 240.10b-18(a)(3)), of shares or other units of any class of the registrant's equity securities that is registered by the registrant pursuant to Section 12 of the Exchange Act (15 U.S.C. 781). Not applicable to open-end management investment companies. ITEM 10. SUBMISSION OF MATTERS TO A VOTE OF SECURITY HOLDERS. Describe any material changes to the procedures by which shareholders may recommend nominees to the registrant's board of directors, where those changes were implemented after the registrant last provided disclosure in response to the requirements of Item 407(c)(2)(iv) of Regulation S-R(17 CFR 229.407)(as required by Item 22(b)(15)) of Schedule 14A (17 CFR 240.14a-101), or this Item. There have been no material changes to the procedures by which the shareholders may recommend nominees to the registrant's board of directors since the registrant last provided disclosure in response to the requirements of Item 407(c)(2)(iv) of Regulation S-R of Schedule 14(A) in its definitive proxy statement, or this item. ITEM 11. CONTROLS AND PROCEDURES. (a) Disclose the conclusions of the registrant's principal executive and principal financials officers, or persons performing similar functions, regarding the effectiveness of the registrant's disclosure controls and procedures (as defined in Rule 30a-3(c) under the Act (17 CFR 270.30a-3(c))) as of a date within 90 days of the filing date of the report that includes the disclosure required by this paragraph, based on the evaluation of these controls and procedures required by Rule 30a-3(b) under the Act (17 CFR 270.30(a)-3(b) and Rules 13a-15(b) or 15d-15(b) under the Exchange Act (17 CFR 240.13a-15(b) or 240.15d-15(b)). The registrant's principal executive officer and principal financial officer have concluded that the registrant's disclosure controls and procedures are effective based on the evaluation of these controls and procedures as of a date within 90 days of the filing date of this report. (b) Disclose any change in the registrant's internal control over financial reporting (as defined in Rule 30a-3(d) under the Act (17CFR 270.30a-3(d)) that occured during the second fiscal quarter of the period covered by this report that has materially affected, or is reasonably likely to materially affect, the registrant's internal control over financial reporting. There were no significant changes in the registrant's internal control over financial reporting that occurred during the second fiscal quarter of the period covered by this report that have materially affected, or are reasonably likely to materially affect, the registrant's internal control over financial reporting. The registrant's principal executive officer and principal financial officer, however, voluntarily are reporting the following information: In August of 2006 the registrant's investment adviser enhanced its internal procedures for reporting performance information required to be included in prospectuses. Those enhancements involved additional internal controls over the appropriateness of performance data generated for this purpose. Such enhancements were made following an internal review which identified prospectuses relating to certain classes of shares of a limited number of registrants where, inadvertently, performance information not reflecting the deduction of applicable sales charges was included. Those prospectuses were revised, and the revised prospectuses were distributed to shareholders. ITEM 12. EXHIBITS. (a) File the exhibits listed below as part of this Form. Letter or number the exhibits in the sequence indicated. (1) Any code of ethics, or amendment thereto, that is the subject of the disclosure required by Item 2, to the extent that the registrant intends to satisfy the Item 2 requirements through filing of an exhibit. (2) A separate certification for each principal executive officer and principal financial officer of the registrant as required by Rule 30a-2(a) under the Act (17 CFR 270.30a-2(a)) , exactly as set forth below: Filed herewith. SIGNATURES [See General Instruction F] Pursuant to the requirements of the Securities Exchange Act of 1934 and the Investment Company Act of 1940, the registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized. (Registrant) Pioneer Series Trust XI By (Signature and Title)* /s/ Lisa M. Jones Lisa M. Jones, President & Chief Executive Officer Date August 29, 2017 Pursuant to the requirements of the Securities Exchange Act of 1934 and the Investment Company Act of 1940, this report has been signed below by the following persons on behalf of the registrant and in the capacities and on the dates indicated. By (Signature and Title)* /s/ Lisa M. Jones Lisa M. Jones, President & Chief Executive Officer Date August 29, 2017 By (Signature and Title)* /s/ Mark E. Bradley Mark E. Bradley, Treasurer & Chief Accounting & Financial Officer Date August 29, 2017 * Print the name and title of each signing officer under his or her signature.