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                                 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 811-06106

                          Pioneer Mid Cap Value Fund
               (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:  October 31


Date of reporting period:  November 1, 2011 through April 30, 2012


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 SHAREOWNERS.


                       Pioneer Mid Cap
                       Value Fund
--------------------------------------------------------------------------------
                       Semiannual Report | April 30, 2012
--------------------------------------------------------------------------------

                       Ticker Symbols:
                       Class A   PCGRX
                       Class B   PBCGX
                       Class C   PCCGX
                       Class R   PCMRX
                       Class Y   PYCGX













                       [LOGO] PIONEER
                              Investments(R)







                      visit us: us.pioneerinvestments.com


Table of Contents



                                                                           
Letter to Shareowners                                                          2

Portfolio Management Discussion                                                4

Portfolio Summary                                                              8

Prices and Distributions                                                       9

Performance Update                                                            10

Comparing Ongoing Fund Expenses                                               15

Schedule of Investments                                                       17

Financial Statements                                                          24

Notes to Financial Statements                                                 33

Approval of Investment Advisory Agreement                                     41

Trustees, Officers and Service Providers                                      45



                   Pioneer Mid Cap Value Fund | Semiannual Report | 4/30/12    1


President's Letter

Dear Shareowner,

The U.S. economy continued its recovery through the first quarter of 2012, even
as broader global concerns weighed on investors. The U.S. unemployment rate
fell to 8.1% in April, and some indicators suggest that it may continue to
trend down. The housing market continued to improve, fueled in part by
record-low mortgage rates. The risk of rising oil prices appeared to recede.
The improved outlook helped U.S. equity markets to perform well in the first
quarter, with the Standard & Poor's 500 Index rising by 12%. For bond
investors, the riskier sectors of the bond market fared the best. The broad
bond market, as measured by the Barclays Capital Aggregate Bond Index, rose by
just 0.3%, while the high-yield bond market, as measured by the Bank of America
Merrill Lynch High Yield Master II Index, rose by 5.15%.

We are cautiously optimistic that the U.S. economy will continue to improve.
But we are also closely monitoring macroeconomic concerns that could change the
market's direction, such as the lingering debt woes in Europe, the state of the
Chinese economy, and the U.S. government's fiscal situation. Clouds have
continued to hover over Europe, as the exit of Greece from the Euro-zone
remains a possibility. Meanwhile, China continues to face a potential slowdown
in economic growth. In the U.S., tax increases and spending cuts scheduled to
take effect at year-end should, unless fiscal policy changes, sharply reduce
the budget deficit -- which would be very good for the country in the longer
run -- but also could potentially stall U.S. economic growth in 2013. All of
these considerations may lead to further market volatility.

At Pioneer, we have long advocated the benefits of staying diversified and
investing for the long term. The strategy has generally performed well for many
investors. Our advice, as always, is to work closely with a trusted financial
advisor to discuss your goals and work together to develop an investment
strategy that meets your individual needs. There is no single best strategy
that works for every investor.

Pioneer's investment professionals focus on finding good opportunities to
invest in both equity and bond markets using the same disciplined investment
approach we have used since 1928. Our strategy is to identify undervalued
individual securities with the greatest potential for success, carefully
weighing risk against reward. Our teams of investment professionals continually



2    Pioneer Mid Cap Value Fund | Semiannual Report | 4/30/12


monitor and analyze the relative valuations of different sectors and securities
globally to help build portfolios that we believe can help you achieve your
investment goals.

We invite you to learn more about Pioneer and our time-tested approach to
investing by consulting with your financial advisor or visiting us online at
us.pioneerinvestments.com. We greatly appreciate your trust in us, and we thank
you for investing with Pioneer.

Sincerely,


/s/ Daniel K. Kingsbury


Daniel K. Kingsbury
President and CEO
Pioneer Investment Management USA, Inc.


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. These statements should
not be relied upon for any other purposes. Past performance is no guarantee of
future results, and there is no guarantee that market forecasts discussed will
be realized.


                   Pioneer Mid Cap Value Fund | Semiannual Report | 4/30/12    3


Portfolio Management Discussion | 4/30/12

Equities produced generally solid results over the six-month period ended April
30, 2012, as investors grew more confident that the domestic economy would
continue to expand and not fall back into recession. In the following
interview, Rod Wright and Timothy Horan discuss the factors that affected the
performance of Pioneer Mid Cap Value Fund during the six-month period. Mr.
Wright, senior vice president and portfolio manager at Pioneer, has been
portfolio manager of the Fund since 1997. Mr. Horan, vice president and
portfolio manager at Pioneer, became co-portfolio manager of the Fund in
October 2011, after four years (2007-2011) as assistant portfolio manager. Mr.
Wright and Mr. Horan are responsible for the day-to-day management of the Fund.

Q How did the Fund perform during the six months ended April 30, 2012?

A Pioneer Mid Cap Value Fund Class A shares returned 10.47% at net asset value
  during the six months ended April 30, 2012, while the Fund's benchmark, the
  Russell Midcap Value Index (the Russell Index), returned 11.48%. During the
  same six-month period, the average return of the 311 mutual funds in Lipper's
  Multi-Cap Value Funds category was 10.51%.

Q How would you describe the investment environment during the six months ended
  April 30, 2012. Also, how did you manage the Fund in that environment, and
  what factors most affected the Fund's performance?

A The domestic equity market began to recover after hitting a low point in early
  October of 2011. During most of the six-month period ended April 30, 2012,
  stocks generally rose amid confidence that the domestic economy was continuing
  to recover, although at a relatively slow pace. After worrying about the
  possibility of a "double-dip" recession in the late summer and early fall of
  2011, the capital markets were relieved to see sustained growth. The nation's
  employment market, which had been slow to show signs of recovery, began
  improving, while corporate profits, industrial output and consumer spending
  all were on the rise. However, the rising market trends suffered some setbacks
  in April of 2012, the final month of the period, as the sovereign-debt
  problems in Greece and some other European nations again flared up. In
  addition, legal challenges to the new federal health care law created
  uncertainty in the market.

  Over the six-month period, we managed the Fund in accordance with its
  long-term investment strategy, emphasizing mid-cap companies with reasonable
  stock valuations. In managing the Fund, we focus on fundamental stock
  research, selecting companies that we believe have solid financial positions,
  good managements, and effective business plans that realistically could drive
  future earnings growth. Our strategy is to focus on stock selection rather
  than on sector bets, concentrating the Fund's assets in


4    Pioneer Mid Cap Value Fund | Semiannual Report | 4/30/12


  quality companies that we believe have the potential to produce solid returns
  over the long term, regardless of short-term market and economic trends.

  During the six months ended April 30, 2012, we kept the Fund's portfolio well
  diversified*, while slightly reducing the number of holdings from
  approximately 85 companies to fewer than 80.

  The Fund's performance, both in absolute terms and relative to the benchmark
  Russell Index, improved substantially during the six-month period ended April
  30, 2012, although performance still slightly lagged that of the benchmark.
  The Fund's stock holdings outperformed the benchmark's performance in five of
  10 sectors during the period. The main source of the Fund's improved
  benchmark-relative performance during the period was stock selection in the
  financials, telecom services, consumer staples, health care and utilities
  sectors. Stock selection in consumer discretionary, materials, industrials,
  energy and information technology underperformed those sectors in the Russell
  Index.

Q What individual investments had the biggest impact on the Fund's performance
  during the six months ended April 30, 2012?

A The top-contributing investment in the Fund's portfolio during the period was
  Wyndham Worldwide, a global hospitality firm involved in three businesses:
  hotel franchising, vacation exchanges, and timeshare sales. The company, led
  by a successful management team, successfully executed its business plan
  during the period, aided by a stable cash flow from its three core businesses.
  Another standout holding for the Fund during the period was SPX, a diversified
  industrial corporation that saw significant improvement in its earnings. SPX's
  businesses include process control systems and equipment, electrical
  components, and transformers. Other holdings that provided significant support
  to Fund results during the period included Toll Brothers, a national
  residential community developer and homebuilder, which saw its business begin
  to improve as the housing market showed signs of bottoming and stabilizing
  after a protracted slump; Allstate Insurance, a property/casualty company that
  repaired some underwriting problems that had caused profits to lag; and Watson
  Pharmaceuticals, a specialty pharmaceutical company with a healthy pipeline of
  developing products. We eventually sold the Fund's position in Toll Brothers.

  Among other holdings that contributed strongly to the Fund's performance
  during the period were Spirit AeroSystems, a commercial aerospace equipment
  company; Discover Financial, the credit card firm; specialty

  * Diversification does not assure a profit or protect against loss in a
    declining market.


                   Pioneer Mid Cap Value Fund | Semiannual Report | 4/30/12    5


  pharmaceutical firm Salix Pharmaceuticals; regional banking firm PNC
  Financial; and Capital One Financial, a banking and credit card corporation.

  On the down side, the Fund did own some companies that posted disappointing
  returns during the six-month period. The single biggest detractor was a
  position in QEP Resources, an energy corporation heavily involved in natural
  gas exploration and production. The company's share price declined as the
  price of natural gas fell. We continue to hold the position in the Fund's
  portfolio. We also have retained the Fund's investment in another notable
  detractor, telecom equipment company Juniper Networks. The company's telecom
  services customers reduced spending on some parts of their networks, which
  held back Juniper's profit growth. We expect network spending to pick up
  again, however, and we think that Juniper is well positioned with new
  products. Another underperforming holding that we retained in the portfolio
  was department store chain Kohl's. The company's stock price was hurt by an
  increase in cotton costs as well as a difficult competitive environment during
  the fall of 2011. We've kept the stock in the Fund's portfolio because we've
  seen the company embark on a series of operational and marketing improvements.
  Combined with declining cotton prices, we think the changes Kohl's has made
  will help to increase revenues and improve profit margins. Another holding in
  the retail space that did not help the Fund's performance during the period
  was Guess?, the global casual clothing retailer aimed at appealing to younger
  women shoppers. While the company continued to grow in the United States and
  in Asia, sales in Europe softened as economic conditions on the Continent
  deteriorated.

Q What is your investment outlook?

A We are enthusiastic about many of the individual stock-buying opportunities
  that we have seen, and we intend to remain focused on finding companies with
  appealing stock prices and bright longer-term prospects that also are
  fundamentally strong. We cannot control shifts in overall economic trends, nor
  can we predict when such shifts may occur, especially given that the potential
  effects of the financial problems in Europe have become a major concern in the
  United States. We do know that we have been identifying many healthy companies
  with excellent business plans, expert management teams and healthy balance
  sheets. We intend to keep the Fund fully invested in the stocks of what we
  believe are such fundamentally solid companies, with particular focus on
  companies with earnings that appear not to be overly sensitive to the problems
  in Europe.


Please refer to the Schedule of Investments on pages 17-23 for a full listing
of Fund securities.


6    Pioneer Mid Cap Value Fund | Semiannual Report | 4/30/12


Investments in mid-sized companies may offer the potential for higher returns,
but are also subject to greater short-term price fluctuations than larger, more
established companies.

Investing in foreign and/or emerging markets securities involves risks relating
to interest rates, currency exchange rates, economic, and political conditions.

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.

These risks may increase share price volatility.

Past performance is no guarantee of future results, and there is no guarantee
that market forecasts discussed will be realized.

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. These opinions should not
be relied upon for any other purposes.


                   Pioneer Mid Cap Value Fund | Semiannual Report | 4/30/12    7


Portfolio Summary | 4/30/12

Portfolio Diversification
--------------------------------------------------------------------------------
(As a percentage of total investment portfolio)

[THE DATA BELOW IS REPRESENTED AS A PIE CHART IN THE PRINTED MATERIAL.]


                                                                        
U.S. Common Stocks                                                         91.9%
International Common Stocks                                                 4.1%
Depositary Receipts for International Stocks                                3.1%
Temporary Cash Investment                                                   0.9%



Sector Distribution
--------------------------------------------------------------------------------
(As a percentage of equity holdings)

[THE DATA BELOW IS REPRESENTED AS A PIE CHART IN THE PRINTED MATERIAL.]


                                                                        
Financials                                                                 29.6%
Industrials                                                                14.5%
Health Care                                                                10.2%
Consumer Discretionary                                                      9.9%
Information Technology                                                      9.4%
Utilities                                                                   7.9%
Energy                                                                      7.0%
Consumer Staples                                                            5.1%
Materials                                                                   4.9%
Telecommunication Services                                                  1.5%



10 Largest Holdings
--------------------------------------------------------------------------------
(As a percentage of equity holdings)*


                                                                     
    1.    Capital One Financial Corp.                                      2.14%
--------------------------------------------------------------------------------
    2.    CIT Group, Inc.                                                  2.03
--------------------------------------------------------------------------------
    3.    Spirit Aerosystems Holdings, Inc.                                1.99
--------------------------------------------------------------------------------
    4.    Teva Pharmaceutical Industries, Ltd. (A.D.R.)                    1.79
--------------------------------------------------------------------------------
    5.    Aon Plc                                                          1.79
--------------------------------------------------------------------------------
    6.    The Allstate Corp.                                               1.79
--------------------------------------------------------------------------------
    7.    Hanesbrands, Inc.                                                1.78
--------------------------------------------------------------------------------
    8.    Fluor Corp.                                                      1.77
--------------------------------------------------------------------------------
    9.    SPX Corp.                                                        1.76
--------------------------------------------------------------------------------
   10.    Noble Energy, Inc.                                               1.71
--------------------------------------------------------------------------------


* This list excludes temporary cash investments and derivative instruments. The
  portfolio is actively managed, and current holdings may be different. The
  holdings listed should not be considered recommendations to buy or sell any
  security listed.


8    Pioneer Mid Cap Value Fund | Semiannual Report | 4/30/12


Prices and Distributions | 4/30/12

Net Asset Value per Share
--------------------------------------------------------------------------------



--------------------------------------------------------------------------------
     Class                  4/30/12                    10/31/11
--------------------------------------------------------------------------------
                                                  
       A                    $21.79                      $19.92
--------------------------------------------------------------------------------
       B                    $17.98                      $16.38
--------------------------------------------------------------------------------
       C                    $17.86                      $16.29
--------------------------------------------------------------------------------
       R                    $21.47                      $19.58
--------------------------------------------------------------------------------
       Y                    $22.79                      $20.87
--------------------------------------------------------------------------------


Distributions per Share: 11/1/11-4/30/12
--------------------------------------------------------------------------------



--------------------------------------------------------------------------------
                   Net
                Investment             Short-Term              Long-Term
     Class        Income             Capital Gains           Capital Gains
--------------------------------------------------------------------------------
                                                        
       A         $0.1959                 $--                     $--
--------------------------------------------------------------------------------
       B         $    --                 $--                     $--
--------------------------------------------------------------------------------
       C         $0.0491                 $--                     $--
--------------------------------------------------------------------------------
       R         $0.1175                 $--                     $--
--------------------------------------------------------------------------------
       Y         $0.2775                 $--                     $--
--------------------------------------------------------------------------------


The Russell Midcap Value Index measures the performance of U.S. mid-cap value
stocks. Index returns 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 10-14.


                   Pioneer Mid Cap Value Fund | Semiannual Report | 4/30/12    9


Performance Update | 4/30/12                                      Class A Shares

Investment Returns
--------------------------------------------------------------------------------
The mountain chart on the right shows the change in value of a $10,000
investment made in Pioneer Mid Cap Value Fund at public offering price,
compared to that of the Russell Midcap Value Index.



 Average Annual Total Returns
 (As of April 30, 2012)
--------------------------------------------------------------------------------
                                      Net Asset     Public Offering
 Period                               Value (NAV)   Price (POP)
--------------------------------------------------------------------------------
                                              
 10 Years                              6.03%          5.41%
 5 Years                              -0.62          -1.79
 1 Year                               -4.58         -10.07
--------------------------------------------------------------------------------


 Expense Ratio
 (Per prospectus dated March 1, 2012)
--------------------------------------------------------------------------------
 Gross
--------------------------------------------------------------------------------

 1.12%
--------------------------------------------------------------------------------


[THE DATA BELOW IS REPRESENTED AS A MOUNTAIN CHART IN THE PRINTED MATERIAL.]

Value of $10,000 Investment



           Pioneer Mid Cap         Russell Midcap
             Value Fund              Value Index
                                 
4/02          $ 9,425                  $10,000
4/03            8,083                    8,651
4/04           11,056                   11,673
4/05           12,822                   14,043
4/06           14,903                   17,518
4/07           17,466                   20,961
4/08           15,851                   18,518
4/09           10,989                   11,710
4/10           15,353                   18,080
4/11           17,742                   21,666
4/12           16,931                   21,491


Call 1-800-225-6292 or visit us.pioneerinvestments.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.


10    Pioneer Mid Cap Value Fund | Semiannual Report | 4/30/12


Performance Update | 4/30/12                                      Class B Shares

Investment Returns
--------------------------------------------------------------------------------
The mountain chart on the right shows the change in value of a $10,000
investment made in Pioneer Mid Cap Value Fund, compared to that of the Russell
Midcap Value Index.




 Average Annual Total Returns
 (As of April 30, 2012)
--------------------------------------------------------------------------------
                                        If           If
 Period                                 Held         Redeemed
--------------------------------------------------------------------------------
                                               
 10 Years                                5.01%        5.01%
 5 Years                                -1.65        -1.65
 1 Year                                 -5.67        -9.44
--------------------------------------------------------------------------------


 Expense Ratio
 (Per prospectus dated March 1, 2012)
--------------------------------------------------------------------------------
 Gross
--------------------------------------------------------------------------------

 2.18%
--------------------------------------------------------------------------------



[THE DATA BELOW IS REPRESENTED AS A MOUNTAIN CHART IN THE PRINTED MATERIAL.]

Value of $10,000 Investment



           Pioneer Mid Cap         Russell Midcap
             Value Fund              Value Index
                                 
4/02          $10,000                  $10,000
4/03            8,506                   8,651
4/04           11,531                  11,673
4/05           13,248                  14,043
4/06           15,252                  17,518
4/07           17,717                  20,961
4/08           15,921                  18,518
4/09           10,928                  11,710
4/10           15,108                  18,080
4/11           17,285                  21,666
4/12           16,305                  21,491


Call 1-800-225-6292 or visit us.pioneerinvestments.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.

"If Held" results represent the percent change in net asset value per share.
Returns would have been lower had sales charges been reflected. "If Redeemed"
returns reflect the deduction of applicable contingent deferred sales charge
(CDSC). Effective December 1, 2004, the period during which a CDSC is applied
to withdrawals was shortened to 5 years. The maximum CDSC for Class B shares is
4% and declines over five years. For more complete information, please see the
prospectus. Note: Shares purchased prior to December 1, 2004, remain subject to
the CDSC in effect at the time you purchased those shares. For performance
information for shares purchased prior to December 1, 2004, please visit
us.pioneerinvestments.com. 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 taxes that a
shareowner would pay on Fund distributions or the redemption of Fund shares.


                  Pioneer Mid Cap Value Fund | Semiannual Report | 4/30/12    11


Performance Update | 4/30/12                                      Class C Shares

Investment Returns
--------------------------------------------------------------------------------
The mountain chart on the right shows the change in value of a $10,000
investment made in Pioneer Mid Cap Value Fund, compared to that of the Russell
Midcap Value Index.



 Average Annual Total Returns
 (As of April 30, 2012)
--------------------------------------------------------------------------------
                                        If           If
 Period                                 Held         Redeemed
--------------------------------------------------------------------------------
                                               
 10 Years                                5.12%        5.12%
 5 Years                                -1.49        -1.49
 1 Year                                 -5.42        -5.42
--------------------------------------------------------------------------------

 Expense Ratio
 (Per prospectus dated March 1, 2012)
--------------------------------------------------------------------------------
 Gross
--------------------------------------------------------------------------------
 1.98%
--------------------------------------------------------------------------------



[THE DATA BELOW IS REPRESENTED AS A MOUNTAIN CHART IN THE PRINTED MATERIAL.]

Value of $10,000 Investment



           Pioneer Mid Cap         Russell Midcap
             Value Fund              Value Index
                                 
4/02          $10,000                  $10,000
4/03            8,502                    8,651
4/04           11,519                   11,673
4/05           13,248                   14,043
4/06           15,270                   17,518
4/07           17,750                   20,961
4/08           15,971                   18,518
4/09           10,979                   11,710
4/10           15,196                   18,080
4/11           17,412                   21,666
4/12           16,468                   21,491


Call 1-800-225-6292 or visit us.pioneerinvestments.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). The performance of Class C shares does not
reflect the 1% front-end sales charge in effect prior to February 1, 2004. If
you paid a 1% sales charge, your returns would be lower than those shown above.
"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.


12    Pioneer Mid Cap Value Fund | Semiannual Report | 4/30/12


Performance Update | 4/30/12                                      Class R Shares

Investment Returns
--------------------------------------------------------------------------------
The mountain chart on the right shows the change in value of a $10,000
investment made in Pioneer Mid Cap Value Fund, compared to that of the Russell
Midcap Value Index.




 Average Annual Total Returns
 (As of April 30, 2012)
--------------------------------------------------------------------------------
                                        If           If
 Period                                 Held         Redeemed
--------------------------------------------------------------------------------
                                               
 10 Years                                5.77%        5.77%
 5 Years                                -0.90        -0.90
 1 Year                                 -4.94        -4.94
--------------------------------------------------------------------------------


 Expense Ratio
 (Per prospectus dated March 1, 2012)
--------------------------------------------------------------------------------
 Gross
--------------------------------------------------------------------------------

 1.42%
--------------------------------------------------------------------------------


[THE DATA BELOW IS REPRESENTED AS A MOUNTAIN CHART IN THE PRINTED MATERIAL.]

Value of $10,000 Investment



           Pioneer Mid Cap         Russell Midcap
             Value Fund              Value Index
                                 
4/02          $10,000                  $10,000
4/03            8,538                    8,651
4/04           11,670                   11,673
4/05           13,521                   14,043
4/06           15,670                   17,518
4/07           18,330                   20,961
4/08           16,581                   18,518
4/09           11,463                   11,710
4/10           15,980                   18,080
4/11           18,432                   21,666
4/12           17,523                   21,491


Call 1-800-225-6292 or visit us.pioneerinvestments.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 performance shown for Class R shares for the period prior to the
commencement of operations of Class R shares on April 1, 2003, is based on the
performance of Class A shares, reduced to reflect the higher distribution and
service fees of Class R shares. For the period beginning on April 1, 2003, the
actual performance of Class R shares is reflected. Class R 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.


                  Pioneer Mid Cap Value Fund | Semiannual Report | 4/30/12    13


Performance Update | 4/30/12                                      Class Y Shares

Investment Returns
--------------------------------------------------------------------------------
The mountain chart on the right shows the change in value of a $5 million
investment made in Pioneer Mid Cap Value Fund, compared to that of the Russell
Midcap Value Index.



 Average Annual Total Returns
 (As of April 30, 2012)
--------------------------------------------------------------------------------
                                        If           If
 Period                                 Held         Redeemed
--------------------------------------------------------------------------------
                                               
 10 Years                                6.52%        6.52%
 5 Years                                -0.20        -0.20
 1 Year                                 -4.17        -4.17
--------------------------------------------------------------------------------


 Expense Ratio
 (Per prospectus dated March 1, 2012)
--------------------------------------------------------------------------------
 Gross
--------------------------------------------------------------------------------

 0.73%
--------------------------------------------------------------------------------


[THE DATA BELOW IS REPRESENTED AS A MOUNTAIN CHART IN THE PRINTED MATERIAL.]

Value of $5 Million Investment



           Pioneer Mid Cap         Russell Midcap
             Value Fund              Value Index
                               
4/02         $5,000,000              $ 5,000,000
4/03          4,310,509                4,325,608
4/04          5,925,263                5,836,289
4/05          6,914,594                7,021,341
4/06          8,069,677                8,758,940
4/07          9,495,395               10,480,575
4/08          8,648,634                9,259,144
4/09          6,026,638                5,855,226
4/10          8,454,856                9,039,924
4/11          9,808,974               10,833,229
4/12          9,400,019               10,745,385



Call 1-800-225-6292 or visit us.pioneerinvestments.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 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.


14    Pioneer Mid Cap Value Fund | Semiannual Report | 4/30/12


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 Mid Cap Value Fund

Based on actual returns from November 1, 2011 through April 30, 2012.



-------------------------------------------------------------------------------------------
 Share Class                          A           B           C           R           Y
-------------------------------------------------------------------------------------------
                                                                   
 Beginning Account Value          $1,000.00   $1,000.00   $1,000.00   $1,000.00   $1,000.00
 on 11/1/11
-------------------------------------------------------------------------------------------
 Ending Account Value             $1,104.70   $1,097.70   $1,099.70   $1,103.10   $1,106.60
 (after expenses) on 4/30/12
-------------------------------------------------------------------------------------------
 Expenses Paid                        $5.76      $11.84      $10.18       $7.53       $3.67
 During Period*
-------------------------------------------------------------------------------------------


* Expenses are equal to the Fund's annualized expense ratio of 1.10%, 2.27%,
  1.95%, 1.44%, and 0.70% for Class A, Class B, Class C, Class R and Class Y
  shares, respectively, multiplied by the average account value over the
  period, multiplied by 182/366 (to reflect the one-half year period).


                  Pioneer Mid Cap Value Fund | Semiannual Report | 4/30/12    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 Mid Cap Value Fund

Based on a hypothetical 5% per year return before expenses, reflecting the
period from November 1, 2011 through April 30, 2012.



-------------------------------------------------------------------------------------------
 Share Class                          A           B           C           R           Y
-------------------------------------------------------------------------------------------
                                                                   
 Beginning Account Value          $1,000.00   $1,000.00   $1,000.00   $1,000.00   $1,000.00
 on 11/1/11
-------------------------------------------------------------------------------------------
 Ending Account Value (after      $1,019.39   $1,013.58   $1,015.17   $1,017.70   $1,021.38
 expenses) on 4/30/12
-------------------------------------------------------------------------------------------
 Expenses Paid                        $5.52      $11.36       $9.77       $7.22       $3.52
 During Period*
-------------------------------------------------------------------------------------------


* Expenses are equal to the Fund's annualized expense ratio of 1.10%, 2.27%,
  1.95%, 1.44%, and 0.70% for Class A, Class B, Class C, Class R and Class Y
  shares, respectively, multiplied by the average account value over the
  period, multiplied by 182/366 (to reflect the one-half year period).


16    Pioneer Mid Cap Value Fund | Semiannual Report | 4/30/12


Schedule of Investments | 4/30/12 (unaudited)



--------------------------------------------------------------------------------------
 Shares                                                                 Value
--------------------------------------------------------------------------------------
                                                                  
               COMMON STOCKS -- 99.1%
               ENERGY -- 7.0%
               Oil & Gas Drilling -- 1.3%
   306,900     Ensco Plc (A.D.R.)                                       $   16,772,085
--------------------------------------------------------------------------------------
               Oil & Gas Equipment & Services -- 1.0%
   161,400     National Oilwell Varco, Inc.                             $   12,227,664
--------------------------------------------------------------------------------------
               Integrated Oil & Gas -- 1.4%
   563,100     QEP Resources, Inc.                                      $   17,349,111
--------------------------------------------------------------------------------------
               Oil & Gas Exploration & Production -- 2.2%
    59,100     Concho Resources, Inc.*                                  $    6,334,338
   212,600     Noble Energy, Inc.                                           21,115,432
                                                                        --------------
                                                                        $   27,449,770
--------------------------------------------------------------------------------------
               Oil & Gas Refining & Marketing -- 0.6%
   283,400     Valero Energy Corp.                                      $    6,999,980
--------------------------------------------------------------------------------------
               Coal & Consumable Fuels -- 0.5%
   601,700     Arch Coal, Inc.                                          $    5,872,592
                                                                        --------------
               Total Energy                                             $   86,671,202
--------------------------------------------------------------------------------------
               MATERIALS -- 4.9%
               Diversified Chemicals -- 1.8%
   234,100     LyondellBasell Industries NV                             $    9,780,698
   122,800     PPG Industries, Inc.                                         12,923,472
                                                                        --------------
                                                                        $   22,704,170
--------------------------------------------------------------------------------------
               Fertilizers & Agricultural Chemicals -- 1.2%
   276,100     The Mosaic Co.                                           $   14,583,602
--------------------------------------------------------------------------------------
               Specialty Chemicals -- 1.1%
   219,300     Ecolab, Inc.                                             $   13,967,217
--------------------------------------------------------------------------------------
               Steel -- 0.8%
   321,000     United States Steel Corp.                                $    9,093,930
                                                                        --------------
               Total Materials                                          $   60,348,919
--------------------------------------------------------------------------------------
               CAPITAL GOODS -- 10.4%
               Aerospace & Defense -- 1.9%
   980,500     Spirit Aerosystems Holdings, Inc.*                       $   24,512,500
--------------------------------------------------------------------------------------
               Construction & Engineering -- 3.3%
   377,900     Fluor Corp.                                              $   21,823,725
   558,700     KBR, Inc.                                                    18,917,582
                                                                        --------------
                                                                        $   40,741,307
--------------------------------------------------------------------------------------
               Construction & Farm Machinery & Heavy Trucks -- 0.9%
    94,100     Cummins, Inc.                                            $   10,899,603
--------------------------------------------------------------------------------------


The accompanying notes are an integral part of these financial statements.

                  Pioneer Mid Cap Value Fund | Semiannual Report | 4/30/12    17


Schedule of Investments | 4/30/12 (unaudited) (continued)



--------------------------------------------------------------------------------------
 Shares                                                                 Value
--------------------------------------------------------------------------------------
                                                                  
               Industrial Machinery -- 4.3%
  459,000      IDEX Corp.                                               $   19,879,290
  281,900      SPX Corp.                                                    21,644,282
  163,101      Stanley Black & Decker, Inc.                                 11,932,469
                                                                        --------------
                                                                        $   53,456,041
                                                                        --------------
               Total Capital Goods                                      $  129,609,451
--------------------------------------------------------------------------------------
               COMMERCIAL SERVICES & SUPPLIES -- 2.7%
               Environmental & Facilities Services -- 1.5%
  683,700      Republic Services, Inc.                                  $   18,712,869
--------------------------------------------------------------------------------------
               Human Resource & Employment Services -- 1.2%
  218,371      Towers Watson & Co.                                      $   14,281,463
                                                                        --------------
               Total Commercial Services & Supplies                     $   32,994,332
--------------------------------------------------------------------------------------
               TRANSPORTATION -- 1.4%
               Airlines -- 1.4%
2,031,000      Southwest Airlines Co.                                   $   16,816,680
                                                                        --------------
               Total Transportation                                     $   16,816,680
--------------------------------------------------------------------------------------
               CONSUMER DURABLES & APPAREL -- 1.8%
               Apparel, Accessories & Luxury Goods -- 1.8%
  779,300      Hanesbrands, Inc.*                                       $   21,991,846
                                                                        --------------
               Total Consumer Durables & Apparel                        $   21,991,846
--------------------------------------------------------------------------------------
               CONSUMER SERVICES -- 2.7%
               Hotels, Resorts & Cruise Lines -- 1.8%
  212,367      Pebblebrook Hotel Trust                                  $    5,113,797
  344,700      Wyndham Worldwide Corp.                                      17,352,198
                                                                        --------------
                                                                        $   22,465,995
--------------------------------------------------------------------------------------
               Specialized Consumer Services -- 0.9%
  284,700      Sotheby's                                                $   11,194,404
                                                                        --------------
               Total Consumer Services                                  $   33,660,399
--------------------------------------------------------------------------------------
               RETAILING -- 5.4%
               Department Stores -- 1.5%
  377,300      Kohl's Corp.                                             $   18,914,049
--------------------------------------------------------------------------------------
               Apparel Retail -- 1.4%
  594,600      Guess?, Inc.                                             $   17,409,888
--------------------------------------------------------------------------------------
               Computer & Electronics Retail -- 1.2%
  419,800      Rent-A-Center, Inc.*                                     $   14,361,358
--------------------------------------------------------------------------------------
               Specialty Stores -- 1.3%
  603,300      Sally Beauty Holdings, Inc.*                             $   16,047,780
                                                                        --------------
               Total Retailing                                          $   66,733,075
--------------------------------------------------------------------------------------


The accompanying notes are an integral part of these financial statements.

18    Pioneer Mid Cap Value Fund | Semiannual Report | 4/30/12




--------------------------------------------------------------------------------------
 Shares                                                                 Value
--------------------------------------------------------------------------------------
                                                                  
               FOOD & STAPLES RETAILING -- 1.0%
               Drug Retail -- 1.0%
  292,600      CVS Caremark Corp.                                       $   13,055,812
                                                                        --------------
               Total Food & Staples Retailing                           $   13,055,812
--------------------------------------------------------------------------------------
               FOOD, BEVERAGE & TOBACCO -- 4.0%
               Distillers & Vintners -- 1.5%
  861,700      Constellation Brands, Inc.*                              $   18,612,720
--------------------------------------------------------------------------------------
               Packaged Foods & Meats -- 2.5%
  539,000      Campbell Soup Co.                                        $   18,234,370
  161,600      The JM Smucker Co.                                           12,868,208
                                                                        --------------
                                                                        $   31,102,578
                                                                        --------------
               Total Food, Beverage & Tobacco                           $   49,715,298
--------------------------------------------------------------------------------------
               HEALTH CARE EQUIPMENT & SERVICES -- 6.4%
               Health Care Equipment -- 1.7%
  787,100      CareFusion Corp.*                                        $   20,393,761
--------------------------------------------------------------------------------------
               Health Care Facilities -- 0.5%
  834,218      Health Management Associates, Inc.*                      $    6,006,370
--------------------------------------------------------------------------------------
               Managed Health Care -- 4.2%
  355,600      Aetna, Inc.                                              $   15,660,624
  429,200      Cigna Corp.                                                  19,841,916
  209,800      Humana, Inc.                                                 16,926,664
                                                                        --------------
                                                                        $   52,429,204
                                                                        --------------
               Total Health Care Equipment & Services                   $   78,829,335
--------------------------------------------------------------------------------------
               PHARMACEUTICALS, BIOTECHNOLOGY & LIFE SCIENCES -- 3.8%
               Pharmaceuticals -- 2.7%
  482,700      Teva Pharmaceutical Industries, Ltd. (A.D.R.)            $   22,078,698
  149,100      Watson Pharmaceuticals, Inc.*                                11,236,176
                                                                        --------------
                                                                        $   33,314,874
--------------------------------------------------------------------------------------
               Life Sciences Tools & Services -- 1.1%
  325,200      Agilent Technologies, Inc.                               $   13,716,936
                                                                        --------------
               Total Pharmaceuticals, Biotechnology & Life Sciences     $   47,031,810
--------------------------------------------------------------------------------------
               BANKS -- 6.2%
               Diversified Banks -- 0.5%
  196,600      Comerica, Inc.                                           $    6,295,132
--------------------------------------------------------------------------------------
               Regional Banks -- 5.7%
  661,400      CIT Group, Inc.*                                         $   25,033,990
  946,000      First Horizon National Corp.                                  8,684,280
  190,100      First Republic Bank/CA*                                       6,279,003
  315,000      PNC Financial Services Group, Inc.                           20,890,800
  454,200      Zions Bancorporation                                          9,261,138
                                                                        --------------
                                                                        $   70,149,211
                                                                        --------------
               Total Banks                                              $   76,444,343
--------------------------------------------------------------------------------------


The accompanying notes are an integral part of these financial statements.

                  Pioneer Mid Cap Value Fund | Semiannual Report | 4/30/12    19


Schedule of Investments | 4/30/12 (unaudited) (continued)



--------------------------------------------------------------------------------------
 Shares                                                                 Value
--------------------------------------------------------------------------------------
                                                                  
               DIVERSIFIED FINANCIALS -- 6.4%
               Specialized Finance -- 1.4%
  440,800      Moody's Corp.                                            $   18,050,760
--------------------------------------------------------------------------------------
               Consumer Finance -- 3.5%
  474,300      Capital One Financial Corp.                              $   26,314,164
  499,600      Discover Financial Services LLC                              16,936,440
                                                                        --------------
                                                                        $   43,250,604
--------------------------------------------------------------------------------------
               Asset Management & Custody Banks -- 1.5%
  342,100      Ameriprise Financial, Inc.                               $   18,545,241
                                                                        --------------
               Total Diversified Financials                             $   79,846,605
--------------------------------------------------------------------------------------
               INSURANCE -- 9.2%
               Insurance Brokers -- 1.8%
  426,000      Aon Plc                                                  $   22,066,800
--------------------------------------------------------------------------------------
               Life & Health Insurance -- 3.3%
  454,200      Aflac, Inc.                                              $   20,457,168
  874,000      Unum Group                                                   20,748,760
                                                                        --------------
                                                                        $   41,205,928
--------------------------------------------------------------------------------------
               Multi-line Insurance -- 0.8%
  450,300      Hartford Financial Services Group, Inc.                  $    9,253,665
--------------------------------------------------------------------------------------
               Property & Casualty Insurance -- 3.3%
  566,900      Axis Capital Holdings, Ltd.                              $   19,285,938
  661,400      The Allstate Corp.                                           22,044,462
                                                                        --------------
                                                                        $   41,330,400
                                                                        --------------
               Total Insurance                                          $  113,856,793
--------------------------------------------------------------------------------------
               REAL ESTATE -- 7.6%
               Diversified REITs -- 0.8%
  702,600      Duke Realty Corp.                                        $   10,412,532
--------------------------------------------------------------------------------------
               Mortgage REITs -- 1.0%
  745,100      Annaly Capital Management, Inc.                          $   12,160,032
--------------------------------------------------------------------------------------
               Office REITs -- 2.2%
  702,100      BioMed Realty Trust, Inc.                                $   13,915,622
  121,300      Boston Properties, Inc.                                      13,130,725
                                                                        --------------
                                                                        $   27,046,347
--------------------------------------------------------------------------------------
               Residential REITs -- 1.0%
  206,300      Equity Residential Trust                                 $   12,675,072
--------------------------------------------------------------------------------------
               Retail REITs -- 1.6%
1,010,300      Kimco Realty Corp.                                       $   19,609,923
--------------------------------------------------------------------------------------
               Specialized REITs -- 1.0%
  754,600      Host Hotels & Resorts, Inc.                              $   12,556,544
                                                                        --------------
               Total Real Estate                                        $   94,460,450
--------------------------------------------------------------------------------------


The accompanying notes are an integral part of these financial statements.

20    Pioneer Mid Cap Value Fund | Semiannual Report | 4/30/12




--------------------------------------------------------------------------------------
 Shares                                                                 Value
--------------------------------------------------------------------------------------
                                                                  
               SOFTWARE & SERVICES -- 4.1%
               Data Processing & Outsourced Services -- 1.3%
  351,300      VeriFone Systems, Inc.*                                  $   16,735,932
--------------------------------------------------------------------------------------
               Application Software -- 1.6%
2,219,304      Compuware Corp.*                                         $   19,352,331
--------------------------------------------------------------------------------------
               Systems Software -- 1.2%
  528,900      Rovi Corp.*                                              $   15,126,540
                                                                        --------------
               Total Software & Services                                $   51,214,803
--------------------------------------------------------------------------------------
               TECHNOLOGY HARDWARE & EQUIPMENT -- 3.0%
               Communications Equipment -- 0.7%
  420,900      Juniper Networks, Inc.*                                  $    9,019,887
--------------------------------------------------------------------------------------
               Computer Storage & Peripherals -- 1.2%
  411,900      SanDisk Corp.*                                           $   15,244,419
--------------------------------------------------------------------------------------
               Technology Distributors -- 1.1%
  308,058      Arrow Electronics, Inc.*                                 $   12,953,839
                                                                        --------------
               Total Technology Hardware & Equipment                    $   37,218,145
--------------------------------------------------------------------------------------
               SEMICONDUCTORS & SEMICONDUCTOR EQUIPMENT -- 2.2%
               Semiconductors -- 2.2%
  440,400      Analog Devices, Inc.                                     $   17,166,792
  282,200      Xilinx, Inc.                                                 10,266,436
                                                                        --------------
                                                                        $   27,433,228
                                                                        --------------
               Total Semiconductors & Semiconductor Equipment           $   27,433,228
--------------------------------------------------------------------------------------
               TELECOMMUNICATION SERVICES -- 1.1%
               Integrated Telecommunication Services -- 1.1%
  365,500      CenturyLink, Inc.                                        $   14,093,680
                                                                        --------------
               Total Telecommunication Services                         $   14,093,680
--------------------------------------------------------------------------------------
               UTILITIES -- 7.8%
               Electric Utilities -- 3.3%
  339,600      American Electric Power Co, Inc.                         $   13,190,064
  438,200      Northeast Utilities                                          16,112,614
  448,500      PPL Corp.                                                    12,266,475
                                                                        --------------
                                                                        $   41,569,153
--------------------------------------------------------------------------------------
               Multi-Utilities -- 4.5%
  573,200      Ameren Corp.                                             $   18,795,228
  897,600      CMS Energy Corp.                                             20,635,824
  274,400      Consolidated Edison, Inc.                                    16,313,080
                                                                        --------------
                                                                        $   55,744,132
                                                                        --------------
               Total Utilities                                          $   97,313,285
--------------------------------------------------------------------------------------
               TOTAL COMMON STOCKS
               (Cost $1,077,288,787)                                    $1,229,339,491
--------------------------------------------------------------------------------------



The accompanying notes are an integral part of these financial statements.

                  Pioneer Mid Cap Value Fund | Semiannual Report | 4/30/12    21


Schedule of Investments | 4/30/12 (unaudited) (continued)



---------------------------------------------------------------------------------------------
 Principal
 Amount ($)                                                                    Value
---------------------------------------------------------------------------------------------
                                                                         
                TEMPORARY CASH INVESTMENTS -- 0.7%
                Repurchase Agreements -- 0.7%
  9,240,000     TD Securities, Inc., 0.17%, dated 4/30/12, repurchase price
                of $9,240,000 plus accrued interest on 5/1/12
                collateralized by $9,424,882 U.S. Treasury
                Note, 1.25%, 4/30/19                                           $    9,240,000
---------------------------------------------------------------------------------------------
                TOTAL TEMPORARY CASH INVESTMENTS
                (Cost $9,240,000)                                              $    9,240,000
---------------------------------------------------------------------------------------------
                TOTAL INVESTMENT IN SECURITIES -- 99.8%
                (Cost $1,086,528,787) (a)                                      $1,238,579,491
---------------------------------------------------------------------------------------------
                OTHER ASSETS & LIABILITIES -- 0.2%                             $    1,870,296
---------------------------------------------------------------------------------------------
                TOTAL NET ASSETS -- 100.0%                                     $1,240,449,787
=============================================================================================


*        Non-income producing security.

(A.D.R.) American Depositary Receipts.

REIT     Real Estate Investment Trust

(a)      At April 30, 2012, the net unrealized gain on investments based on cost
         for federal income tax purposes of $1,090,677,318 was as follows:


                                                                                    
           Aggregate gross unrealized gain for all investments in which there is an
             excess of value over tax cost                                             $172,638,301
           Aggregate gross unrealized loss for all investments in which there is an
             excess of tax cost over value                                              (24,736,128)
                                                                                       ------------
           Net unrealized gain                                                         $147,902,173
                                                                                       ============



The accompanying notes are an integral part of these financial statements.

22    Pioneer Mid Cap Value Fund | Semiannual Report | 4/30/12


Purchases and sales of securities (excluding temporary cash investments) for
the six months ended April 30, 2012 aggregated $597,531,617 and $754,396,844,
respectively.

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.)
  Level 3 -- significant unobservable inputs (including the Fund's own
             assumptions in determining fair value of investments)

Generally, equity securities are categorized as Level 1, fixed income
securities and senior loans as Level 2 and securities using fair value methods
are categorized as Level 3. See Notes to Financial Statements -- Note 1A.

The following is a summary of the inputs used as of April 30, 2012, in valuing
the Fund's assets:



--------------------------------------------------------------------------------------------
                           Level 1             Level 2          Level 3       Total
--------------------------------------------------------------------------------------------
                                                                  
 Common Stocks             $1,229,339,491      $       --       $--           $1,229,339,491
 Repurchase Agreements                 --       9,240,000        --                9,240,000
--------------------------------------------------------------------------------------------
 Total                     $1,229,339,491      $9,240,000       $--           $1,238,579,491
============================================================================================


The accompanying notes are an integral part of these financial statements.

                  Pioneer Mid Cap Value Fund | Semiannual Report | 4/30/12    23


Statement of Assets and Liabilities | 4/30/12 (unaudited)


                                                       
ASSETS:
  Investment in securities (cost $1,086,528,787)          $1,238,579,491
  Cash                                                         6,619,427
  Receivables --
   Investment securities sold                                  8,256,980
   Fund shares sold                                              952,100
   Dividends                                                     339,397
  Other                                                           52,306
------------------------------------------------------------------------
     Total assets                                         $1,254,799,701
------------------------------------------------------------------------
LIABILITIES:
  Payables --
   Investment securities purchased                        $   10,092,643
   Fund shares repurchased                                     3,671,759
  Due to affiliates                                              496,928
  Accrued expenses                                                88,584
------------------------------------------------------------------------
     Total liabilities                                    $   14,349,914
------------------------------------------------------------------------
NET ASSETS:
  Paid-in capital                                         $1,188,698,786
  Undistributed net investment income                          1,569,604
  Accumulated net realized loss on investments              (101,869,307)
  Net unrealized gain on investments                         152,050,704
------------------------------------------------------------------------
     Total net assets                                     $1,240,449,787
========================================================================
NET ASSET VALUE PER SHARE:
(No par value, unlimited number of shares authorized)
  Class A (based on $872,975,145/40,058,691 shares)       $        21.79
  Class B (based on $28,923,223/1,608,248 shares)         $        17.98
  Class C (based on $73,356,622/4,106,923 shares)         $        17.86
  Class R (based on $40,880,664/1,904,294 shares)         $        21.47
  Class Y (based on $224,314,133/9,843,812 shares)        $        22.79
MAXIMUM OFFERING PRICE:
  Class A ($21.79 [divided by] 94.25%)                    $        23.12
========================================================================



The accompanying notes are an integral part of these financial statements.

24    Pioneer Mid Cap Value Fund | Semiannual Report | 4/30/12


Statement of Operations (unaudited)

For the Six Months Ended 4/30/12


                                                                       
INVESTMENT INCOME:
  Dividends (net of foreign taxes withheld of $64,834)      $13,010,602
  Interest                                                        5,062
  Income from securities loaned, net                             24,257
----------------------------------------------------------------------------------------
     Total investment income                                                $ 13,039,921
----------------------------------------------------------------------------------------
EXPENSES:
  Management fees
   Basic Fee                                                $ 3,562,694
   Performance Adjustment                                        (3,208)
  Transfer agent fees and expenses
   Class A                                                      629,662
   Class B                                                       74,246
   Class C                                                       58,592
   Class R                                                        5,899
   Class Y                                                        5,976
  Distribution fees
   Class A                                                    1,089,363
   Class B                                                      156,019
   Class C                                                      360,680
   Class R                                                      111,922
  Shareholders communication expense                            698,888
  Administrative reimbursements                                 186,644
  Custodian fees                                                 22,386
  Registration fees                                              42,475
  Professional fees                                              58,891
  Printing expense                                               14,666
  Fees and expenses of nonaffiliated Trustees                    20,292
  Miscellaneous                                                  44,171
----------------------------------------------------------------------------------------
     Total expenses                                                         $  7,140,258
----------------------------------------------------------------------------------------
       Net investment income                                                $  5,899,663
----------------------------------------------------------------------------------------
REALIZED AND UNREALIZED GAIN (LOSS) ON INVESTMENTS:
  Net realized gain on:
   Investments                                              $43,318,876
   Class action                                                 235,688     $ 43,554,564
----------------------------------------------------------------------------------------
  Change in net unrealized gain on investments                              $ 82,873,762
----------------------------------------------------------------------------------------
  Net gain on investments                                                   $126,428,326
----------------------------------------------------------------------------------------
  Net increase in net assets resulting from operations                      $132,327,989
========================================================================================



The accompanying notes are an integral part of these financial statements.

                  Pioneer Mid Cap Value Fund | Semiannual Report | 4/30/12    25


Statement of Changes in Net Assets



-----------------------------------------------------------------------------------------------
                                                             Six Months
                                                             Ended
                                                             4/30/12             Year Ended
                                                             (unaudited)         10/31/11
-----------------------------------------------------------------------------------------------
                                                                           
FROM OPERATIONS:
Net investment income                                        $    5,899,663      $   12,317,879
Net realized gain on investments and class action                43,554,564         116,572,261
Change in net unrealized gain (loss) on investments              82,873,762        (104,213,662)
-----------------------------------------------------------------------------------------------
   Net increase in net assets resulting from operations      $  132,327,989      $   24,676,478
-----------------------------------------------------------------------------------------------
DISTRIBUTIONS TO SHAREOWNERS:
Net investment income:
   Class A ($0.20 and $0.10 per share, respectively)         $   (8,388,953)     $   (5,044,203)
   Class C ($0.05 and $0.00 per share, respectively)               (211,500)                 --
   Class R ($0.12 and $0.05 per share, respectively)               (273,535)           (130,618)
   Class Y ($0.28 and $0.19 per share, respectively)             (3,796,094)         (3,123,335)
-----------------------------------------------------------------------------------------------
     Total distributions to shareowners                      $  (12,670,082)     $   (8,298,156)
-----------------------------------------------------------------------------------------------
FROM FUND SHARE TRANSACTIONS:
Net proceeds from sale or exchange of shares                 $   60,668,115      $  185,261,561
Reinvestment of distributions                                    10,428,167           6,733,668
Cost of shares repurchased                                     (272,720,753)       (431,841,062)
-----------------------------------------------------------------------------------------------
   Net decrease in net assets resulting from Fund share
     transactions                                            $ (201,624,471)     $ (239,845,833)
-----------------------------------------------------------------------------------------------
   Net decrease in net assets                                $  (81,966,564)     $ (223,467,511)
NET ASSETS:
Beginning of period                                           1,322,416,351       1,545,883,862
-----------------------------------------------------------------------------------------------
End of period                                                $1,240,449,787      $1,322,416,351
-----------------------------------------------------------------------------------------------
Undistributed net investment income                          $    1,569,604      $    8,883,695
===============================================================================================


The accompanying notes are an integral part of these financial statements.

26    Pioneer Mid Cap Value Fund | Semiannual Report | 4/30/12




---------------------------------------------------------------------------------------------------
                                     '12 Shares     '12 Amount        '11 Shares      '11 Amount
                                     (unaudited)    (unaudited)
---------------------------------------------------------------------------------------------------
                                                                          
CLASS A
Shares sold                           1,422,998     $  29,615,747       4,077,567     $  85,668,724
Reinvestment of distributions           394,639         7,833,596         222,381         4,707,836
Less shares repurchased              (5,921,687)     (123,152,178)    (10,885,426)     (228,058,943)
---------------------------------------------------------------------------------------------------
   Net decrease                      (4,104,050)    $ (85,702,835)     (6,585,478)    $(137,682,383)
===================================================================================================
CLASS B
Shares sold or exchanged                 30,642     $     512,985          96,787     $   1,716,717
Less shares repurchased                (462,465)       (7,911,467)     (1,107,227)      (19,183,208)
---------------------------------------------------------------------------------------------------
   Net decrease                        (431,823)    $  (7,398,482)     (1,010,440)    $ (17,466,491)
===================================================================================================
Class C
Shares sold                             189,811     $   3,263,707         436,706     $   7,613,921
Reinvestment of distributions            10,526           171,692              --                --
Less shares repurchased                (567,643)       (9,585,515)     (1,298,167)      (22,281,454)
---------------------------------------------------------------------------------------------------
   Net decrease                        (367,306)    $  (6,150,116)       (861,461)    $ (14,667,533)
===================================================================================================
Class R
Shares sold                             149,749     $   3,061,738         558,870     $  11,589,960
Reinvestment of distributions            13,542           265,148           6,003           125,238
Less shares repurchased                (740,756)      (15,188,884)     (1,120,157)      (23,246,544)
---------------------------------------------------------------------------------------------------
   Net decrease                        (577,465)    $ (11,861,998)       (555,284)    $ (11,531,346)
===================================================================================================
Class Y
Shares sold                           1,128,212     $  24,213,938       3,608,357     $  78,672,239
Reinvestment of distributions           104,138         2,157,731          86,039         1,900,594
Less shares repurchased              (5,175,102)     (116,882,709)     (6,523,631)     (139,070,913)
---------------------------------------------------------------------------------------------------
   Net decrease                      (3,942,752)    $ (90,511,040)     (2,829,235)    $ (58,498,080)
===================================================================================================


The accompanying notes are an integral part of these financial statements.

                  Pioneer Mid Cap Value Fund | Semiannual Report | 4/30/12    27


Financial Highlights



----------------------------------------------------------------------------------------------------
                                                             Six Months
                                                             Ended
                                                             4/30/12        Year Ended    Year Ended
                                                             (unaudited)    10/31/11      10/31/10
----------------------------------------------------------------------------------------------------
                                                                                 
Class A
Net asset value, beginning of period                         $  19.92       $  19.81      $    16.91
----------------------------------------------------------------------------------------------------
Increase (decrease) from investment operations:
 Net investment income                                       $   0.10       $   0.17      $     0.12
 Net realized and unrealized gain (loss) on investments          1.97           0.04            2.90
----------------------------------------------------------------------------------------------------
  Net increase (decrease) from investment operations         $   2.07       $   0.21      $     3.02
Distributions to shareowners:
 Net investment income                                          (0.20)         (0.10)          (0.12)
 Net realized gain                                                 --             --              --
----------------------------------------------------------------------------------------------------
Net increase (decrease) in net asset value                   $   1.87       $   0.11      $     2.90
----------------------------------------------------------------------------------------------------
Net asset value, end of period                               $  21.79       $  19.92      $    19.81
====================================================================================================
Total return*                                                   10.47%          1.04%          17.96%
Ratio of net expenses to average net assets+                     1.10%**        1.12%           1.23%
Ratio of net investment income to average net assets+            0.90%**        0.78%           0.61%
Portfolio turnover rate                                            93%**          72%             89%
Net assets, end of period (in thousands)                     $872,975       $879,872      $1,005,305
Ratios with reduction for fees paid indirectly:
 Net expenses                                                    1.10%**        1.12%           1.23%
 Net investment income                                           0.90%**        0.78%           0.61%
====================================================================================================




----------------------------------------------------------------------------------------------------
                                                             Year Ended     Year Ended    Year Ended
                                                             10/31/09       10/31/08      10/31/07
----------------------------------------------------------------------------------------------------
                                                                                 
Class A
Net asset value, beginning of period                         $    15.04     $    25.62    $    25.33
----------------------------------------------------------------------------------------------------
Increase (decrease) from investment operations:
 Net investment income                                       $     0.14     $     0.17    $     0.11
 Net realized and unrealized gain (loss) on investments            1.91          (8.99)         3.58
----------------------------------------------------------------------------------------------------
  Net increase (decrease) from investment operations         $     2.05     $    (8.82)   $     3.69
Distributions to shareowners:
 Net investment income                                            (0.18)         (0.10)        (0.10)
 Net realized gain                                                   --          (1.66)        (3.30)
----------------------------------------------------------------------------------------------------
Net increase (decrease) in net asset value                   $     1.87     $   (10.58)   $     0.29
----------------------------------------------------------------------------------------------------
Net asset value, end of period                               $    16.91     $    15.04    $    25.62
====================================================================================================
Total return*                                                     13.87%        (36.70)%       16.47%
Ratio of net expenses to average net assets+                       1.43%          1.13%         1.03%
Ratio of net investment income to average net assets+              0.89%          0.80%         0.48%
Portfolio turnover rate                                              81%            61%           54%
Net assets, end of period (in thousands)                     $1,046,729     $1,101,941    $2,048,721
Ratios with reduction for fees paid indirectly:
 Net expenses                                                      1.43%          1.13%         1.02%
 Net investment income                                             0.89%          0.80%         0.49%
====================================================================================================


*  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.
+  Ratios with no reduction for fees paid indirectly.

The accompanying notes are an integral part of these financial statements.

28  Pioneer Mid Cap Value Fund | Semiannual Report | 4/30/12




-------------------------------------------------------------------------------------
                                                           Six Months
                                                           Ended
                                                           4/30/12         Year Ended
                                                           (unaudited)     10/31/11
-------------------------------------------------------------------------------------
                                                                     
Class B
Net asset value, beginning of period                       $ 16.38         $ 16.38
-------------------------------------------------------------------------------------
Increase (decrease) from investment operations:
 Net investment income (loss)                              $  0.00(b)      $ (0.03)
 Net realized and unrealized gain (loss) on investments       1.60            0.03
-------------------------------------------------------------------------------------
  Net increase (decrease) from investment operations       $  1.60         $    --
Distributions to shareowners:
 Net investment income                                          --              --
 Net realized gain                                              --              --
-------------------------------------------------------------------------------------
Net increase (decrease) in net asset value                 $  1.60         $    --
-------------------------------------------------------------------------------------
Net asset value, end of period                             $ 17.98         $ 16.38
=====================================================================================
Total return*                                                 9.77%           0.00%
Ratio of net expenses to average net assets+                  2.27%**         2.18%
Ratio of net investment loss to average net assets+          (0.25)%**       (0.28)%
Portfolio turnover rate                                         93%**           72%
Net assets, end of period (in thousands)                   $28,923         $33,410
Ratios with reduction for fees paid indirectly:
 Net expenses                                                 2.27%**         2.18%
 Net investment loss                                         (0.25)%**       (0.28)%
=====================================================================================




------------------------------------------------------------------------------------------------------------------
                                                             Year Ended    Year Ended     Year Ended    Year Ended
                                                             10/31/10      10/31/09       10/31/08      10/31/07
------------------------------------------------------------------------------------------------------------------
                                                                                            
Class B
Net asset value, beginning of period                         $ 14.03       $ 12.47        $ 21.65       $  22.00
------------------------------------------------------------------------------------------------------------------
Increase (decrease) from investment operations:
 Net investment income (loss)                                $ (0.05)      $  0.01(a)     $ (0.01)      $  (0.10)
 Net realized and unrealized gain (loss) on investments         2.40          1.57          (7.51)          3.05
------------------------------------------------------------------------------------------------------------------
  Net increase (decrease) from investment operations         $  2.35       $  1.58        $ (7.52)      $   2.95
Distributions to shareowners:
 Net investment income                                            --         (0.02)            --             --
 Net realized gain                                                --            --          (1.66)         (3.30)
------------------------------------------------------------------------------------------------------------------
Net increase (decrease) in net asset value                   $  2.35       $  1.56        $ (9.18)      $  (0.35)
------------------------------------------------------------------------------------------------------------------
Net asset value, end of period                               $ 16.38       $ 14.03        $ 12.47       $  21.65
==================================================================================================================
Total return*                                                  16.75%        12.66%        (37.32)%        15.38%
Ratio of net expenses to average net assets+                    2.29%         2.51%          2.09%          1.97%
Ratio of net investment loss to average net assets+            (0.45)%       (0.17)%        (0.16)%        (0.46)%
Portfolio turnover rate                                           89%           81%            61%            54%
Net assets, end of period (in thousands)                     $49,961       $59,595        $70,729       $149,348
Ratios with reduction for fees paid indirectly:
 Net expenses                                                   2.29%         2.51%          2.08%          1.95%
 Net investment loss                                           (0.45)%       (0.17)%        (0.15)%        (0.44)%
==================================================================================================================


*   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.
+   Ratios with no reduction for fees paid indirectly.
(a) The amount shown for a share outstanding does not correspond with the
    aggregate gain on investments for the period due to the timing of sales and
    repurchases of shares in relation to fluctuating market values of the
    investments of the Fund.
(b) Rounds to less than $0.01 per share.

The accompanying notes are an integral part of these financial statements.

                    Pioneer Mid Cap Value Fund | Semiannual Report | 4/30/12  29


Financial Highlights (continued)



--------------------------------------------------------------------------------------------------------
                                                                Six Months
                                                                Ended
                                                                4/30/12         Year Ended    Year Ended
                                                                (unaudited)     10/31/11      10/31/10
--------------------------------------------------------------------------------------------------------
                                                                                     
Class C
Net asset value, beginning of period                            $ 16.29         $ 16.26       $ 13.92
--------------------------------------------------------------------------------------------------------
Increase (decrease) from investment operations:
 Net investment income (loss)                                   $  0.01         $ (0.01)      $ (0.04)
 Net realized and unrealized gain (loss) on investments            1.61            0.03          2.39
--------------------------------------------------------------------------------------------------------
  Net increase (decrease) from investment operations            $  1.62         $  0.03       $  2.35
Distributions to shareowners:
 Net investment income                                            (0.05)             --         (0.01)
 Net realized gain                                                   --              --            --
--------------------------------------------------------------------------------------------------------
Net increase (decrease) in net asset value                      $  1.57         $  0.03       $  2.34
--------------------------------------------------------------------------------------------------------
Net asset value, end of period                                  $ 17.86         $ 16.29       $ 16.26
========================================================================================================
Total return*                                                      9.97%           0.19%        16.88%
Ratio of net expenses to average net assets+                       1.95%**         1.98%         2.13%
Ratio of net investment income (loss) to average net assets+       0.05%**        (0.08)%       (0.29)%
Portfolio turnover rate                                              93%**           72%           89%
Net assets, end of period (in thousands)                        $73,357         $72,873       $86,750
Ratios with reduction for fees paid indirectly:
 Net expenses                                                      1.95%**         1.98%         2.13%
 Net investment income (loss)                                      0.05%**        (0.08)%       (0.29)%
========================================================================================================




---------------------------------------------------------------------------------------------------------
                                                                 Year Ended     Year Ended     Year Ended
                                                                 10/31/09       10/31/08       10/31/07
---------------------------------------------------------------------------------------------------------
                                                                                      
Class C
Net asset value, beginning of period                             $ 12.38        $ 21.48        $  21.84
---------------------------------------------------------------------------------------------------------
Increase (decrease) from investment operations:
 Net investment income (loss)                                    $  0.01(a)     $  0.00(b)     $  (0.08)
 Net realized and unrealized gain (loss) on investments             1.57          (7.44)           3.02
---------------------------------------------------------------------------------------------------------
  Net increase (decrease) from investment operations             $  1.58        $ (7.44)       $   2.94
Distributions to shareowners:
 Net investment income                                             (0.04)            --              --
 Net realized gain                                                    --          (1.66)          (3.30)
---------------------------------------------------------------------------------------------------------
Net increase (decrease) in net asset value                       $  1.54        $ (9.10)       $  (0.36)
---------------------------------------------------------------------------------------------------------
Net asset value, end of period                                   $ 13.92        $ 12.38        $  21.48
=========================================================================================================
Total return*                                                      12.87%        (37.23)%         15.46%
Ratio of net expenses to average net assets+                        2.35%          1.98%           1.87%
Ratio of net investment income (loss) to average net assets+       (0.03)%        (0.05)%         (0.36)%
Portfolio turnover rate                                               81%            61%             54%
Net assets, end of period (in thousands)                         $86,536        $92,814        $187,566
Ratios with reduction for fees paid indirectly:
 Net expenses                                                       2.35%          1.97%           1.86%
 Net investment income (loss)                                      (0.03)%        (0.04)%         (0.35)%
=========================================================================================================


*   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.
+   Ratios with no reduction for fees paid indirectly.
(a) The amount shown for a share outstanding does not correspond with the
    aggregate gain on investments for the period due to the timing of sales and
    repurchases of shares in relation to fluctuating market values of the
    investments of the Fund.
(b) Amount rounds to less than $0.01 per share.

The accompanying notes are an integral part of these financial statements.

30  Pioneer Mid Cap Value Fund | Semiannual Report | 4/30/12




-------------------------------------------------------------------------------------
                                                           Six Months
                                                           Ended
                                                           4/30/12         Year Ended
                                                           (unaudited)     10/31/11
-------------------------------------------------------------------------------------
                                                                     
Class R
Net asset value, beginning of period                       $ 19.58         $ 19.48
-------------------------------------------------------------------------------------
Increase (decrease) from investment operations:
 Net investment income                                     $  0.08         $  0.10
 Net realized and unrealized gain (loss) on investments       1.93            0.05
-------------------------------------------------------------------------------------
  Net increase (decrease) from investment operations       $  2.01         $  0.15
Distributions to shareowners:
 Net investment income                                       (0.12)          (0.05)
 Net realized gain                                              --              --
-------------------------------------------------------------------------------------
Net increase (decrease) in net asset value                 $  1.89         $  0.10
-------------------------------------------------------------------------------------
Net asset value, end of period                             $ 21.47         $ 19.58
=====================================================================================
Total return*                                                10.31%           0.73%
Ratio of net expenses to average net assets+                  1.44%**         1.42%
Ratio of net investment income to average net assets+         0.58%**         0.48%
Portfolio turnover rate                                         93%**           72%
Net assets, end of period (in thousands)                   $40,881         $48,605
Ratios with reduction for fees paid indirectly:
 Net expenses                                                 1.44%**         1.42%
 Net investment income                                        0.58%**         0.48%
=====================================================================================




----------------------------------------------------------------------------------------------------------------
                                                             Year Ended    Year Ended   Year Ended    Year Ended
                                                             10/31/10      10/31/09     10/31/08      10/31/07
----------------------------------------------------------------------------------------------------------------
                                                                                          
Class R
Net asset value, beginning of period                         $ 16.66       $ 14.82      $ 25.26       $ 25.06
----------------------------------------------------------------------------------------------------------------
Increase (decrease) from investment operations:
 Net investment income                                       $  0.05       $  0.08      $  0.11       $  0.05
 Net realized and unrealized gain (loss) on investments         2.87          1.91        (8.85)         3.53
----------------------------------------------------------------------------------------------------------------
  Net increase (decrease) from investment operations         $  2.92       $  1.99      $ (8.74)      $  3.58
Distributions to shareowners:
 Net investment income                                         (0.10)        (0.15)       (0.04)        (0.08)
 Net realized gain                                                --            --        (1.66)        (3.30)
----------------------------------------------------------------------------------------------------------------
Net increase (decrease) in net asset value                   $  2.82       $  1.84      $(10.44)      $  0.20
----------------------------------------------------------------------------------------------------------------
Net asset value, end of period                               $ 19.48       $ 16.66      $ 14.82       $ 25.26
================================================================================================================
Total return*                                                  17.58%        13.63%      (36.83)%       16.14%
Ratio of net expenses to average net assets+                    1.50%         1.66%        1.40%         1.33%
Ratio of net investment income to average net assets+           0.33%         0.62%        0.54%         0.18%
Portfolio turnover rate                                           89%           81%          61%           54%
Net assets, end of period (in thousands)                     $59,172       $57,029      $40,614       $62,741
Ratios with reduction for fees paid indirectly:
 Net expenses                                                   1.50%         1.66%        1.40%         1.33%
 Net investment income                                          0.33%         0.62%        0.54%         0.18%
================================================================================================================


*  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.
+  Ratios with no reduction for fees paid indirectly.

The accompanying notes are an integral part of these financial statements.

                    Pioneer Mid Cap Value Fund | Semiannual Report | 4/30/12  31


Financial Highlights (continued)



--------------------------------------------------------------------------------------
                                                            Six Months
                                                            Ended
                                                            4/30/12         Year Ended
                                                            (unaudited)     10/31/11
--------------------------------------------------------------------------------------
                                                                      
Class Y
Net asset value, beginning of period                        $  20.87        $  20.75
--------------------------------------------------------------------------------------
Increase (decrease) from investment operations:
 Net investment income                                      $   0.13        $   0.29
 Net realized and unrealized gain (loss) on investments         2.07            0.02
--------------------------------------------------------------------------------------
  Net increase (decrease) from investment operations        $   2.20        $   0.31
Distributions to shareowners:
 Net investment income                                         (0.28)          (0.19)
 Net realized gain                                                --              --
--------------------------------------------------------------------------------------
Net increase (decrease) in net asset value                  $   1.92        $   0.12
--------------------------------------------------------------------------------------
Net asset value, end of period                              $  22.79        $  20.87
======================================================================================
Total return*                                                  10.66%           1.44%
Ratio of net expenses to average net assets+                    0.70%**         0.73%
Ratio of net investment income to average net assets+           1.34%**         1.18%
Portfolio turnover rate                                           93%**           72%
Net assets, end of period (in thousands)                    $224,314        $287,657
Ratios with reduction for fees paid indirectly:
 Net expenses                                                   0.70%**         0.73%
 Net investment income                                          1.34%**         1.18%
======================================================================================




----------------------------------------------------------------------------------------------------------------
                                                            Year Ended    Year Ended    Year Ended    Year Ended
                                                            10/31/10      10/31/09      10/31/08      10/31/07
----------------------------------------------------------------------------------------------------------------
                                                                                          
Class Y
Net asset value, beginning of period                        $  17.70      $  15.76      $  26.73      $  26.31
----------------------------------------------------------------------------------------------------------------
Increase (decrease) from investment operations:
 Net investment income                                      $   0.19      $   0.21      $   0.26      $   0.19
 Net realized and unrealized gain (loss) on investments         3.05          2.01         (9.39)         3.74
----------------------------------------------------------------------------------------------------------------
  Net increase (decrease) from investment operations        $   3.24      $   2.22      $  (9.13)     $   3.93
Distributions to shareowners:
 Net investment income                                         (0.19)        (0.28)        (0.18)        (0.21)
 Net realized gain                                                --            --         (1.66)        (3.30)
----------------------------------------------------------------------------------------------------------------
Net increase (decrease) in net asset value                  $   3.05      $   1.94      $ (10.97)     $   0.42
----------------------------------------------------------------------------------------------------------------
Net asset value, end of period                              $  20.75      $  17.70      $  15.76      $  26.73
================================================================================================================
Total return*                                                  18.46%        14.41%       (36.41)%       16.84%
Ratio of net expenses to average net assets+                    0.84%         0.95%         0.71%         0.68%
Ratio of net investment income to average net assets+           0.99%         1.35%         1.23%         0.82%
Portfolio turnover rate                                           89%           81%           61%           54%
Net assets, end of period (in thousands)                    $344,695      $293,436      $236,643      $354,485
Ratios with reduction for fees paid indirectly:
 Net expenses                                                   0.84%         0.95%         0.71%         0.68%
 Net investment income                                          0.99%         1.35%         1.23%         0.82%
================================================================================================================


*  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.
+  Ratios with no reduction for fees paid indirectly.

The accompanying notes are an integral part of these financial statements.

32  Pioneer Mid Cap Value Fund | Semiannual Report | 4/30/12


Notes to Financial Statements | 4/30/12 (unaudited)

1. Organization and Significant Accounting Policies

Pioneer Mid Cap Value Fund (the Fund) is a Delaware statutory trust. The Fund
is registered under the Investment Company Act of 1940 as a diversified,
open-end management investment company. The investment objective of the Fund is
to seek capital appreciation by investing in a diversified portfolio of
securities consisting primarily of common stocks.

The Fund offers five classes of shares designated as Class A, Class B, Class C,
Class R and Class Y shares. Effective as of the close of business on December
31, 2009, Class B shares are no longer offered to new or existing shareholders,
except that dividends and/or capital gain distributions may continue to be
reinvested in Class B shares, and shareholders may exchange their Class B
shares for Class B shares of other Pioneer funds, as permitted by existing
exchange privileges. 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 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. Class B shares convert to Class A shares
approximately eight years after the date of purchase.

The Fund's financial statements have been prepared in conformity with U.S.
generally accepted accounting principles that require the management of the
Fund to, among other things, make estimates and assumptions that affect the
reported amounts of assets and liabilities, the disclosure of contingent assets
and liabilities at the date of the financial statements, and the reported
amounts of income, expenses and gains and losses on investments during the
reporting period. Actual results could differ from those estimates.


                  Pioneer Mid Cap Value Fund | Semiannual Report | 4/30/12    33


The following is a summary of significant accounting policies followed by the
Fund in the preparation of its financial statements, which are consistent with
those policies generally accepted in the investment company industry:

A. Security Valuation

   Security transactions are recorded as of trade date. 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. In computing
   the net asset value, securities that have traded on an exchange are valued at
   the last sale price on the principal exchange where they are traded.
   Securities that have not traded on the date of valuation, or securities for
   which sale prices are not available, generally are valued at the mean between
   the last bid and asked prices. Short-term fixed income securities with
   remaining maturities of sixty days or less generally are valued at amortized
   cost. Money market mutual funds are valued at net asset value.

   Trading in foreign 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.

   Securities for which market prices and/or quotations are not readily
   available or are considered to be unreliable are valued using fair value
   methods pursuant to procedures adopted by the Board of Trustees. 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 from exchange prices.

   At April 30, 2012, there were no securities that were valued using fair value
   methods (other than securities that were valued using prices supplied by
   independent pricing services). 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.

   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 is recorded on the accrual
   basis. Dividend and interest income are reported net of unrecoverable foreign
   taxes withheld at the applicable country rates.

   Gains and losses on sales of investments are calculated on the identified
   cost method for both financial reporting and federal income tax purposes.


34    Pioneer Mid Cap Value Fund | Semiannual Report | 4/30/12


B. 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 taxable income and net realized capital gains, if any, to its
   shareowners. Therefore, no federal income tax provision is required. Tax
   years for the prior three fiscal years remain subject to examination by
   federal and state tax authorities.

   The amounts and characterizations of distributions to shareowners for
   financial reporting purposes are determined in accordance with federal income
   tax rules. Therefore, the sources of the Fund's distributions may be shown in
   the accompanying financial statements as from or in excess of net investment
   income or as from net realized gain on investment transactions, or as from
   paid-in capital, depending on the type of book/tax differences that may
   exist.

   The tax character of current year distributions payable will be determined at
   the end of the Fund's taxable year. The tax character of distributions paid
   during the year ended October 31, 2011 was as follows:



--------------------------------------------------------------------------------
                                                                            2011
--------------------------------------------------------------------------------
                                                                   
   Distributions paid from:
   Ordinary income                                                    $8,298,156
--------------------------------------------------------------------------------
      Total                                                           $8,298,156
================================================================================


   The following shows the components of distributable earnings on a federal
   income tax basis at October 31, 2011:



--------------------------------------------------------------------------------
                                                                            2011
--------------------------------------------------------------------------------
                                                                
   Distributable earnings:
   Undistributed ordinary income                                   $   8,249,529
   Capital loss carryforward                                        (141,184,846)
   Net unrealized gain                                                65,028,411
--------------------------------------------------------------------------------
      Total                                                        $ (67,906,906)
================================================================================


   The difference between book-basis and tax-basis net unrealized gain is
   attributable to the tax deferral of losses on wash sales and the tax-basis
   adjustments on Real Estate Investment Trust (REIT) holdings.

C. Fund Shares

   The Fund records sales and repurchases of its shares as of trade date.
   Pioneer Funds Distributor, Inc. (PFD), the principal underwriter for the Fund
   and a wholly owned indirect subsidiary of UniCredit S.p.A. (UniCredit),
   earned $27,937 in underwriting commissions on the sale of Class A shares
   during the six months ended April 30, 2012.


                  Pioneer Mid Cap Value Fund | Semiannual Report | 4/30/12    35


D. 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. During the period, the Fund recognized gains of $235,688 in
   settlement of class action lawsuits from several different companies, as
   reflected on the Statement of Operations.

   Distribution fees are calculated based on the average daily net asset value
   attributable to Class A, Class B, Class C, and Class R shares of the Fund,
   respectively (see Note 4). Class Y shares do not pay distribution fees. All
   expenses and fees paid to the transfer agent, Pioneer Investment Management
   Shareholder Services, Inc. (PIMSS), 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 B, Class C, Class R and Class Y
   shares can reflect different transfer agent and distribution expense rates.

E. Risks

   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 or 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.

F. Securities Lending

   The Fund may lend securities in its portfolio to certain broker-dealers or
   other institutional investors. When entering into a securities loan
   transaction, the Fund typically receives cash collateral from the borrower
   equal to at least the value of the securities loaned, which is invested in
   temporary investments. Credit Suisse AG, New York Branch, as the Fund's
   securities lending agent, manages the Fund's securities lending collateral.
   The income earned on the investment of collateral is shared with the borrower
   and the lending agent in payment of any rebate due to the borrower with
   respect to the securities loan, and in compensation for the lending agent's
   services to the Fund. The Fund also continues to receive payments in lieu of
   dividends or interest on the securities loaned. Gain or loss on the value of
   the loaned securities that may occur during the term of the loan will be for
   the account of the Fund. The


36    Pioneer Mid Cap Value Fund | Semiannual Report | 4/30/12


   amount of the collateral is required to be adjusted daily to reflect any
   price fluctuation in the value of the loaned securities. If the required
   market value of the collateral is less than the value of the loaned
   securities, the borrower is required to deliver additional collateral for the
   account of the Fund prior to the close of business on that day. The Fund has
   the right, under the lending agreement, to terminate the loan and recover the
   securities from the borrower with prior notice. The Fund is required to
   return the cash collateral to the borrower and could suffer a loss if the
   value of the collateral, as invested, has declined. At April 30, 2012, the
   Fund had no securities on loan.

G. Repurchase Agreements

   With respect to repurchase agreements entered into by the Fund, the value of
   the underlying securities (collateral), including accrued interest, is
   required to be equal to or in excess of the repurchase price. The collateral
   for all repurchase agreements is held in safekeeping in the customer-only
   account of the Fund's custodian or a subcustodian of the Fund. The Fund's
   investment adviser, Pioneer Investment Management, Inc. (PIM), is responsible
   for determining that the value of the collateral remains at least equal to
   the repurchase price.

2. Management Agreement

PIM, a wholly owned indirect subsidiary of UniCredit, manages the Fund's
portfolio. Management fees are calculated daily at the annual rate of 0.70% of
the Fund's average daily net assets up to $500 million, 0.65% on the next $500
million, 0.625% on the next $3 billion and 0.60% on the excess over $4 billion.
The basic fee (fee before performance adjustment) can increase or decrease by a
maximum of 0.10% based on the investment performance of the Fund's Class A
shares as compared to the Russell Midcap Value Index. The performance
comparison is made for a rolling 36-month period. In addition, Pioneer
contractually limits any positive adjustment of the Fund's management fee to
0.10% of the Fund's average daily net assets on an annual basis (i.e., to a
maximum of 0.80% after the performance adjustment). For the six months ended
April 30, 2012, the aggregate performance adjustment resulted in a decrease of
$3,208 to the basic fee. For the six months ended April 30, 2012, the net
management fee was equivalent to 0.55% of the Fund's average daily net assets.

PIM has contractually agreed to limit ordinary operating expenses of the Fund
to the extent required to reduce Fund expenses to 1.43% and 1.18% of the
average daily net assets attributable to Class A and Class Y shares,
respectively. These expense limitations are in effect through June 1, 2012 for
Class A and Class Y shares. Class B, Class C and Class R shares do not have an
expense limitation. There can be no assurance that PIM will extend the expense
limitation agreement for a class of shares beyond the date referred to above.


                  Pioneer Mid Cap Value Fund | Semiannual Report | 4/30/12    37


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
$112,937 in management fees, administrative costs and certain other
reimbursements payable to PIM at April 30, 2012.

3. Transfer Agent

PIMSS, a wholly owned indirect subsidiary of UniCredit, provides substantially
all transfer agent and shareowner services to the Fund at negotiated rates.

In addition, the Fund reimburses PIMSS for out-of-pocket expenses incurred by
PIMSS related to shareholder communications activities such as proxy and
statement mailings, outgoing phone calls and omnibus relationship contracts.

For the six months ended April 30, 2012, such out-of-pocket expenses by class
of shares were as follows:



--------------------------------------------------------------------------------
 Shareholder Communications:
--------------------------------------------------------------------------------
                                 
 Class A                                                                $414,335
 Class B                                                                  28,223
 Class C                                                                  63,158
 Class R                                                                  67,715
 Class Y                                                                 125,457
--------------------------------------------------------------------------------
    Total                                                               $698,888
================================================================================


Included in "Due to affiliates" reflected on the Statement of Assets and
Liabilities is $334,388 in transfer agent fees and out-of-pocket reimbursements
payable to PIMSS at April 30, 2012.

4. Distribution and Service Plans

The Fund has adopted a Distribution Plan pursuant to Rule 12b-1 of the
Investment Company Act of 1940 with respect to its Class A, Class B, Class C
and Class R shares. Pursuant to the Plan, the Fund pays 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 PFD
1.00% of the average daily net assets attributable to Class B and Class C
shares. The fee for Class B and 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 B
and Class C shares. Pursuant to the Plan, the Fund further pays PFD 0.50% of
the average daily net assets attributable to Class R shares for distribution
services. Included in "Due to affiliates" reflected on the Statement of Assets
and Liabilities is $49,603 in distribution fees payable to PFD at April 30,
2012.


38    Pioneer Mid Cap Value Fund | Semiannual Report | 4/30/12


The Fund also has adopted a separate service plan for Class R shares (Service
Plan). The Service Plan authorizes the Fund to pay securities dealers, plan
administrators or other service organizations that agree to provide certain
services to retirement plans or plan participants holding shares of the Fund a
service fee of up to 0.25% of the Fund's average daily net assets attributable
to Class R shares held by such plans.

In addition, redemptions of each class of shares (except Class R and 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. Class B shares that are redeemed
within five years of purchase are subject to a CDSC at declining rates
beginning at 4.00%, based on the lower of cost or market value of shares being
redeemed. Redemptions of Class C shares within one year 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 R or Class Y shares. Proceeds from the CDSCs are paid to PFD. For the six
months ended April 30, 2012, CDSCs in the amount of $30,363 were paid to PFD.

5. Expense Offset Arrangements

The Fund has entered into certain expense offset arrangements with PIMSS which
may result in a reduction in the Fund's total expenses due to interest earned
on cash held by PIMSS. For the six months ended April 30, 2012, the Fund's
expenses were not reduced under such arrangements.

6. 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 effect until January 20, 2012 was in the amount of $165
million. Under such facility, interest on borrowings was payable at the higher
of the London Interbank Offered Rate (LIBOR) on the borrowing date plus 1.25%
on an annualized basis or the Federal Funds Rate on the borrowing date plus
1.25% on an annualized basis. The credit facility in effect as of February 15,
2012 is in the amount of $215 million. Under such facility, depending on the
type of loan, interest on borrowings is payable at LIBOR plus 0.90% 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 Euro dollar rate on the borrowing date. The Funds pay an annual
commitment fee to participate in a credit facility. The commitment fee


                  Pioneer Mid Cap Value Fund | Semiannual Report | 4/30/12    39


is allocated among participating Funds based on an allocation schedule set
forth in the credit agreement. For the six months ended April 30, 2012, the
Fund had no borrowings under a credit facility.


40    Pioneer Mid Cap Value Fund | Semiannual Report | 4/30/12


Approval of Investment Advisory Agreement

Pioneer Investment Management, Inc. (PIM) serves as the investment adviser to
Pioneer Mid Cap Value Fund (the Fund) pursuant to an investment advisory
agreement between PIM and the Fund. In order for PIM to remain the investment
adviser of the Fund, the Trustees of the Fund must determine annually whether
to renew the investment advisory agreement for the Fund.

The contract review process began in March 2011 as the Trustees of the Fund
agreed on, among other things, an overall approach and timeline for the
process. In July 2011, the Trustees approved the format of the contract review
materials and submitted their formal request to PIM to furnish information
necessary to evaluate the terms of the investment advisory agreement. The
contract review materials were provided to the Trustees in July 2011 and
September 2011. After reviewing and discussing the materials, the Trustees
submitted a request for additional information to PIM, and materials were
provided in response to this request. Meetings of the Independent Trustees of
the Fund were held in July, September, October, and November, 2011 to review
and discuss the contract review materials. In addition, the Trustees took into
account the information related to the Fund provided to the Trustees at each
regularly scheduled meeting.

At a meeting held on November 29, 2011, based on their evaluation of the
information provided by PIM and third parties, the Trustees of the Fund,
including the Independent Trustees voting separately, unanimously approved the
renewal of the investment advisory agreement for another year. In considering
the renewal of the investment advisory agreement, 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 determining to approve the renewal of the agreement.

Nature, Extent and Quality of Services
The Trustees considered the nature, extent and quality of the services that had
been provided by PIM to the Fund, taking into account the investment objective
and strategy of the Fund. The Trustees reviewed the terms of the investment
advisory agreement. The Trustees also reviewed PIM's investment approach for
the Fund, its research process and its process for trade execution. The
Trustees considered the resources of PIM and the personnel of PIM who provide
investment management services to the Fund. The Trustees considered the
non-investment resources and personnel of PIM involved in PIM's services to the
Fund, including PIM's compliance and legal resources and personnel. The
Trustees also considered the substantial attention and high priority given by
PIM's senior management to the Pioneer fund complex. In addition, the


                  Pioneer Mid Cap Value Fund | Semiannual Report | 4/30/12    41


Trustees considered PIM's plans to increase resources in its investment
management function and other enhancements to PIM's advisory capabilities.

The Trustees considered that PIM 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. The Trustees also considered that, as administrator,
PIM is responsible for the administration of the Fund's business and other
affairs. The Trustees considered the fees paid to PIM for the provision of
administration services.

Based on these considerations, the Trustees concluded that the nature, extent
and quality of services that had been provided by PIM to the Fund were
satisfactory and consistent with the terms of the investment advisory
agreement.

Performance of the Fund
The Trustees considered the performance results of the Fund over various time
periods. They reviewed information comparing the Fund's performance with the
performance of its peer group of funds as classified by Morningstar, Inc.
(Morningstar), an independent provider of investment company data, and with the
performance of the Fund's benchmark index. The Trustees considered that the
Fund's annualized total return was in the fourth quintile of its Morningstar
category for the one year period ended June 30, 2011, in the fifth quintile of
its Morningstar category for the three year period ended June 30, 2011, and in
the third quintile of its Morningstar category for the five year period ended
June 30, 2011. (In all quintile rankings referred to throughout this
disclosure, first quintile is most favorable to the Fund's shareowners. Thus,
highest relative performance would be first quintile and lowest relative
expenses would also be first quintile.) The Trustees discussed the Fund's
performance record and PIM's plan for improving the Fund's performance. The
Trustees agreed that they would closely monitor the implementation of PIM's
plan for improving the Fund's performance

Management Fee and Expenses
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 Trust
Research and Consulting, LLC (Strategic Insight), an independent third party.

The Trustees considered that the Fund's management fee for the twelve months
ended June 30, 2011 was in the first quintile relative to the management fees
paid by other funds in its Morningstar peer group for the comparable period.
The Trustees considered that the Fund's management fee is adjusted upward or
downward based on the Fund's performance and considered the breakpoints in


42    Pioneer Mid Cap Value Fund | Semiannual Report | 4/30/12


the management fee schedule and the reduced fee rates above certain asset
levels. The Trustees noted that the Fund's low management fee relative to other
funds in its Morningstar peer group was related to the Fund's underperformance.
The Trustees considered that the Fund's expense ratio for the twelve months
ended June 30, 2011 was in the third quintile relative to its Strategic Insight
peer group for the comparable period.

The Trustees reviewed gross and net management fees charged by PIM to its
institutional and other clients, including publicly offered European funds,
U.S. registered investment companies (in a sub-advisory capacity), and
unaffiliated foreign and domestic separate accounts. The Trustees also
considered PIM's costs in providing services to the Fund and to its other
clients and considered the differences in management fees and profit margins
for PIM's Fund and non-Fund services. In evaluating the fees associated with
PIM's client accounts, the Trustees took into account the respective demands,
resources and complexity associated with the Fund and 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 the
investment advisory agreement with the Fund, PIM performs 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 entrepreneurial risks associated with PIM's management of the Fund
and the other client accounts. The Trustees concluded that the management fee
payable by the Fund to PIM was reasonable in relation to the nature and quality
of the services provided by PIM.

Profitability
The Trustees considered information provided by PIM regarding the profitability
of PIM with respect to the advisory services provided by PIM to the Fund,
including the methodology used by PIM in allocating certain of its costs to the
management of the Fund. The Trustees also considered PIM's profit margin in
connection with the overall operation of the Fund. They further reviewed the
financial results realized by PIM and its affiliates from non-fund businesses.
The Trustees considered PIM'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 PIM's profitability with respect to the management of the Fund
was not unreasonable.

Economies of Scale
The Trustees considered PIM'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 funds and fund


                  Pioneer Mid Cap Value Fund | Semiannual Report | 4/30/12    43


shareholders. The Trustees noted the breakpoints in the management fee
schedule. The Trustees recognize that economies of scale are difficult to
identify and quantify, rarely identifiable on a Fund-by-Fund basis, and that,
among other factors that may be relevant, are the following: fee levels,
expense subsidization, investment by PIM in research and analytical
capabilities and PIM's commitment and resource allocation to the Funds. 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
particularly, for example during the recent difficult periods for financial
markets, as the level of services was maintained notwithstanding a significant
decline in PIM's fee revenues from the Funds. Accordingly, the Trustees
concluded that economies of scale, if any, were being appropriately shared with
the Fund.

Other Benefits
The Trustees considered the other benefits to PIM from its relationship with
the Fund. The Trustees considered the character and amount of fees paid by the
Fund, other than under the investment advisory agreement, for services provided
by PIM and its affiliates. The Trustees further considered the revenues and
profitability of PIM's businesses other than the fund business. The Trustees
also considered the benefits to the Fund and to PIM and its affiliates from the
use of "soft" commission dollars generated by the Fund to pay for research and
brokerage services. The Trustees considered the intangible benefits to PIM by
virtue of its relationship with the Fund and the other Pioneer funds. The
Trustees concluded that the receipt of these benefits was reasonable in the
context of the overall relationship between PIM and the Fund.

Conclusion
After consideration of the factors described above as well as other factors,
the Trustees, including all of the Independent Trustees, concluded that the
investment advisory agreement between PIM and the Fund, including the fees
payable thereunder, was fair and reasonable and voted to approve the proposed
renewal of the investment advisory agreement for the Fund.


44    Pioneer Mid Cap Value Fund | Semiannual Report | 4/30/12


Trustees, Officers and Service Providers

Trustees
John F. Cogan, Jr., Chairman
David R. Bock
Mary K. Bush
Benjamin M. Friedman
Margaret B.W. Graham
Daniel K. Kingsbury
Thomas J. Perna
Marguerite A. Piret

Officers
John F. Cogan, Jr., President
Daniel K. Kingsbury, Executive  Vice President
Mark E. Bradley, Treasurer
Christopher J. Kelley, Secretary

Investment Adviser and Administrator
Pioneer Investment Management, Inc.


Custodian
Brown Brothers Harriman & Co.


Principal Underwriter
Pioneer Funds Distributor, Inc.


Legal Counsel
Bingham McCutchen LLP


Shareowner Services and Transfer Agent
Pioneer Investment Management Shareholder 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 us.pioneerinvestments.com. This information is also available on
the Securities and Exchange Commission's web site at www.sec.gov.


                  Pioneer Mid Cap Value Fund | Semiannual Report | 4/30/12    45


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52    Pioneer Mid Cap Value Fund | Semiannual Report | 4/30/12


How to Contact 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:
--------------------------------------------------------------------------------
PIMSS, Inc.
P.O. Box 55014
Boston, Massachusetts 02205-5014


Our toll-free fax                                               1-800-225-4240


Our internet e-mail address                 ask.pioneer@pioneerinvestments.com
(for general questions about Pioneer only)



Visit our web site: us.pioneerinvestments.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 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.




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 10(a), 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 accountant's 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 registrant's accountant
for services rendered to the registrant, and rendered to the registrant's
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 registrant's audit committee of the board of trustees
has considered whether the provision of non-audit services that were rendered to
the registrant's 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 registrants 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 I Investments in securities of unaffiliated issuers
as of the close of the reporting period as set forth in 210.12-
12 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 registrants portfolio (Portfolio Manager). Also state each Portfolio
Managers 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 registrants equity securities
that is registered by the registrant pursuant to Section 12 of the
Exchange Act (15 U.S.C. 781). Instruction to paragraph (a). Disclose
all purchases covered by this Item, including purchases that do not
satisfy the conditions of the safe harbor of Rule 10b-18 under the
Exchange Act (17 CFR 240.10b-18), made in the period covered by the
report. Provide disclosures covering repurchases made on a monthly basis.
For example, if the reporting period began on January 16 and ended on
July 15, the chart would show repurchases for the months from January 16
through February 15, February 16 through March 15, March 16 through
April 15, April 16 through May 15, May 16 through June 15, and June 16
through July 15.

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 registrants board of directors, where
those changes were implemented after the registrant last provided
disclosure in response to the requirements of Item 7(d)(2)(ii)(G)
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 registrants board of
directors since the registrant last provided disclosure in response
to the requirements of Item 7(d)(2)(ii)(G) 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 officer or
officers and principal financial officer or officers, or persons performing
similar functions, about the effectiveness of the registrant's disclosure
controls and procedures (as defined in Rule 30a-2(c) under the Act (17 CFR
270.30a-2(c))) based on their evaluation of these controls and procedures as of
a date within 90 days of the filing date of the report that includes the
disclosure required by this paragraph.

The registrant's principal executive officer
and principal financial officer have
concluded that the registrant's disclosure
controls and procedures are effective based
on their evaluation of these controls and
procedures as of a date within 90 days of the
filing date of this report.


(b) Disclose whether or not there were significant changes in the registrant's
internal controls or in other factors that could significantly affect these
controls subsequent to the date of their evaluation, including any corrective
actions with regard to significant deficiencies and material weaknesses.

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.

File the exhibits listed below as part of this Form. Letter or number the
exhibits in the sequence indicated.

(a) 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.



(b) A separate certification for each principal executive officer and principal
financial officer of the registrant as required by Rule 30a-2 under the Act
(17 CFR 270.30a-2).

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 Mid Cap Value Fund


By (Signature and Title)* /s/ John F. Cogan, Jr.
John F. Cogan, Jr, President

Date June 29, 2012


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/ John F. Cogan, Jr.
John F. Cogan, Jr., President

Date June 29, 2012


By (Signature and Title)* /s/ Mark Bradley
Mark Bradley, Treasurer & Chief Accounting & Financial Officer

Date June 29, 2012

* Print the name and title of each signing officer under his or her signature.