As filed with the Securities and Exchange Commission on September 27, 2005

                                                             File No. 333-126371


                                  United States
                       Securities and Exchange Commission
                             Washington, D.C. 20549

                                    FORM N-14


             REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933

                           Pre-Effective Amendment No.
                         Post-Effective Amendment No. 1

                        (Check appropriate box or boxes)


                           PIONEER MID CAP VALUE FUND

               (Exact Name of Registrant as Specified in Charter)


                                 (617) 742-7825
                        (Area Code and Telephone Number)

                  60 State Street, Boston, Massachusetts 02109
 (Address of Principal Executive Offices: Number, Street, City, State, Zip Code)

                            Dorothy E. Bourassa, Esq.
                       Pioneer Investment Management, Inc.
                                 60 State Street
                           Boston, Massachusetts 02109
                     (Name and Address of Agent for Service)

Copies to:  David C. Phelan, Esq.
            Wilmer Cutler Pickering Hale and Dorr LLP
            60 State Street
            Boston, Massachusetts 02109

It is proposed that this filing will become effective immediately upon filing
pursuant to paragraph (d) of Rule 462 under the Securities Act of 1933, as
amended.


There have been no changes to the proxy statement/prospectus or statement of
additional information as filed with Pre-Effective Amendment No. 1 to the
Registrant's Registration Statement on Form N-14 (File No. 333-126371), as filed
with the Commission on August 18, 2005 (Accession No. 0001145443-05-001805).


                                     PART C

                                OTHER INFORMATION
                           PIONEER MID CAP VALUE FUND

ITEM 15.  INDEMNIFICATION

No change from the information set forth in Item 25 of the most recently filed
Registration Statement of Pioneer Mid Cap Value Fund (the "Registrant") on Form
N-1A under the Securities Act of 1933 and the Investment Company Act of 1940
(File Nos. 33-34801 and 811-06106) as filed with the Securities and Exchange
Commission on February 25, 2005 (Accession No. 0001016964-05-000076), which
information is incorporated herein by reference.

ITEM 16.  EXHIBITS


                                                                                        
(1)(a)         Agreement and Declaration of Trust                                             (1)

(1)(b)         Certificates of Amendments to Agreement and Declaration of Trust               (2) (4)
(1)(c)         Amendment to Agreement and Declaration of Trust to establish Investor Class    (7)
               Shares
(2)            Restated By-Laws                                                               (3)

(3)            Not applicable

(4)            Agreement and Plan of Reorganization                                           (*)

(5)            Reference is made to Exhibits (1) and (2) hereof

(6)(a)         Management Contract                                                            (7)

(6)(b)         Expense Limitation Agreement for Investor Class Shares                         (7)

(7)(a)         Underwriting Agreement with Pioneer Funds Distributor, Inc.                    (4)

(7)(b)         Dealer Sales Agreement                                                         (6)

(8)            Not applicable

(9)            Custodian Agreement with Brown Brothers Harriman & Co.                         (7)

(10)(a)        Multiple Class Plan Pursuant to Rule 18f-3                                     (7)

(10)(b)        Class A Distribution Plan                                                      (4)




                                                                                        
(10)(c)        Class B Distribution Plan                                                      (4)

(10)(d)        Class C Distribution Plan                                                      (4)

(10)(e)        Class R Distribution Plan                                                      (5)

(10)(f)        Class R Service Plan                                                           (5)

(11)           Opinion of Counsel (legality of securities being offered)                      (8)

(12)           Opinion as to Tax Matters                                                      (*)

(13)(a)        Investment Company Service Agreement with Pioneering Services
               Corporation                                                                    (7)

(13)(b)        Administration Agreement with Pioneer Investment
               Management, Inc.                                                               (7)

(13)(c)        Services Agreement for Class Y Shares                                          (*)

(14)           Consent(s) of Independent Registered Public Accounting Firm                    (9)

(15)           Not applicable

(16)           Powers of Attorney                                                             (7)

(17)(a)        Code of Ethics                                                                 (7)

(17)(b)        Form of Proxy Card                                                             (8)


(1) Previously filed. Incorporated herein by reference from the exhibits filed
with Post-Effective Amendment No. 11 to the Registrant's Registration Statement
on Form N-1A (File Nos. 33-34801; 811-06106), as filed with the Securities and
Exchange Commission on June 30, 1998 (Accession no. 0001016964-98-000074).

(2) Previously filed. Incorporated herein by reference from the exhibits filed
with Post-Effective Amendment No. 15 to the Registrant's Registration Statement
on Form N-1A (File Nos. 33-34801; 811-06106), as filed with the Securities and
Exchange Commission on February 28, 2000 (Accession no. 0001016964-00-000032).

(3) Previously filed. Incorporated herein by reference from the exhibits filed
with Post-Effective Amendment No. 16 to the Registrant's Registration Statement
on Form N-1A (File Nos. 33-34801; 811-06106), as filed with the Securities and
Exchange Commission on March 1, 2001 (Accession no. 0001016964-01-000040).


(4) Previously filed. Incorporated herein by reference from the exhibits filed
with Post-Effective Amendment No. 18 to the Registrant's Registration Statement
on Form N-1A (File Nos. 33-34801; 811-06106), as filed with the Securities and
Exchange Commission on March 1, 2002 (Accession no. 0001016964-02-000042).

(5) Previously filed. Incorporated herein by reference from the exhibits filed
with Post-Effective Amendment No. 19 to the Registrant's Registration Statement
on Form N-1A (File Nos. 33-34801; 811-06106), as filed with the Securities and
Exchange Commission on January 13, 2003 (Accession no. 0000863334-03-000002).

(6) Previously filed. Incorporated herein by reference from the exhibits filed
with Post-Effective Amendment No. 21 to the Registrant's Registration Statement
on Form N-1A (File Nos. 33-34801; 811-06106), as filed with the Securities and
Exchange Commission on February 23, 2004 (Accession no. 0001016964-04-000053).

(7) Previously filed. Incorporated herein by reference from the exhibits filed
with Post-Effective Amendment No. 25 to the Registrant's Registration Statement
on Form N-1A (File Nos. 33-34801; 811-06106), as filed with the Securities and
Exchange Commission on February 25, 2005 (Accession no. 0001016964-04-000076).

(8) Previously filed. Incorporated herein by reference from the exhibits filed
with the Registrant's Registration Statement on Form N-14 (File No. 333-126371),
as filed with the Securities and Exchange Commission on July 5, 2005 (Accession
no. 0001145443-05-001511).

(9) Previously filed. Incorporated herein by reference from the exhibits filed
with Pre-Effective Amendment No. 1 to the Registrant's Registration Statement on
Form N-14 (File No. 333-126371), as filed with the Securities and Exchange
Commission on August 18, 2005 (Accession no. 0001145443-05-001805).

(*) Filed herewith.

ITEM 17. UNDERTAKINGS.

(1) The undersigned Registrant agrees that prior to any public reoffering of the
securities registered through the use of a prospectus which is part of this
Registration Statement by any person or party which is deemed to be an
underwriter within the meaning of Rule 145(c) of the Securities Act of 1933, the
reoffering prospectus will contain the information called for by the applicable
registration form for the reofferings by persons who may be deemed underwriters,
in addition to the information called for by the other items of the applicable
form.

(2) The undersigned Registrant agrees that every prospectus that is filed under
paragraph (1) above will be filed as part of an amendment to the Registration
Statement and will not be used until the amendment is effective, and that, in
determining any liability under the Securities Act of 1933, each post-effective
amendment shall be


deemed to be a new registration statement for the securities offered therein,
and the offering of the securities at that time shall be deemed to be the
initial bona fide offering of them.

(3) The undersigned Registrant agrees that it shall file a final executed
version of the legal and consent opinion as to tax matters as an exhibit to the
subsequent post-effective amendment to its registration statement on Form N-14
filed with the SEC upon the consummation of the reorganization contemplated by
this Registration Statement on Form N-14.

(4) Insofar as indemnification for liability arising under the Securities Act of
1933 may be permitted to directors, officers and controlling persons of the
Registrant pursuant to the foregoing provisions, or otherwise the Registrant has
been advised that in the opinion of the Securities and Exchange Commission such
indemnification is against public policy as expressed in the Act and is,
therefore, unenforceable. In the event that a claim for indemnification against
such liabilities (other than the payment by the Registrant of expenses incurred
or paid by a director, officer or controlling person of the Registrant in the
successful defense of any action, suit or proceeding) is asserted by such
director, officer or controlling person in connection with the securities being
registered, the Registrant will, unless in the opinion of its counsel the matter
has been settled by controlling precedent, submit to a court of appropriate
jurisdiction the question whether such indemnification by it is against public
policy as expressed in the Act and will be governed by the final adjudication of
such issue.


                                   SIGNATURES

         Pursuant to the requirements of the Securities Act of 1933, as amended,
this Registration Statement on Form N-14 has been signed on behalf of the
Registrant, in the City of Boston and the Commonwealth of Massachusetts, on the
27th day of September, 2005

                                 Pioneer Mid Cap Value Fund

                                 /s/ Osbert M. Hood
                                 --------------------------------------------

                                 Osbert M. Hood
                                 Executive Vice President


         Pursuant to the requirements of the Securities Act of 1933, this
Registration Statement has been signed below by the following persons in the
capacities and on the dates indicated.



      Signature                              Title                                Date

                                                                      
         *                            Chairman of the Board,
- ---------------------------           Trustee, and President
John F. Cogan, Jr.

         *                            Chief Financial Officer,
- ---------------------------           Principal Accounting
Vincent Nave                          Officer, and Treasurer

         *
- ---------------------------
Mary K. Bush                          Trustee

         *                            Trustee
- ---------------------------
David R. Bock
                                      Trustee
         *
- ---------------------------
Margaret B.W. Graham                  Trustee

         *                            Trustee
- ---------------------------
Marguerite A. Piret

         *                            Trustee
- ---------------------------
John Winthrop



* By: /s/ Osbert M. Hood                                  September 27, 2005
      -----------------------------
      Osbert M. Hood, Attorney-in-Fact


                                  EXHIBIT INDEX

The following exhibits are filed as part of this Registration Statement:



Exhibit No.       Description

         
(4)         Agreement and Plan of Reorganization

(12)        Opinion as to Tax Matters

(13)(c)     Services Agreement for Class Y Shares