485BPOS

File No. 333-157312

As filed with the Securities and Exchange Commission on June 5, 2009

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM N-14

REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933x

Pre-Effective Amendment No.[ ]

Post-Effective Amendment No. 1x

PIONEER MID CAP VALUE FUND

(Exact Name of Registrant as Specified in Charter)

60 State Street, Boston, Massachusetts 02109

(Address of Principal Executive Offices) (Zip Code)

(617) 742-7825

Registrant’s Telephone Number, including Area Code:

Dorothy E. Bourassa, Pioneer Investment Management, Inc.

60 State Street, Boston, Massachusetts 02109

(Name and Address of Agent for Service)

With Copies To:

Roger P. Joseph, Esq.

Bingham McCutchen LLP

One Federal Street, Boston, Massachusetts 02110

Approximate Date of Proposed Public Offering: As soon as practicable after

the effective date of this Registration Statement.

Title of Securities Being Registered:

Class A shares, Class C shares and Class Y shares

______________________________________

The Registrant has registered an indefinite amount of securities under the Securities Act of 1933, as amended, pursuant to Section 24(f) under the Investment Company Act of 1940, as amended; accordingly, no fee is payable herewith because of reliance upon Section 24(f).

This Registration Statement will become effective on June 5, 2009, pursuant to Rule 485(b) under the Securities Act of 1933, as amended.

__________________________________________________________________________

Part A - Proxy Statement/Prospectus and Part B - Statement of Additional Information are incorporated herein by reference to Pre-Effective Amendment No. 1 to the Registrant's Registration Statement on Form N-14 as filed with the Securities and Exchange Commission on March 30, 2009.

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. 033-34801 and 811-06106), as filed with the Securities and Exchange Commission on February 26, 2009 (Accession No. 0000863334-09-000004), which information is incorporated herein by reference.

ITEM 16. EXHIBITS

(1)(a)	Amended and Restated Agreement and Declaration of Trust	(vii)
(1)(b)	Certificate of Trust	(i)
(1)(c)	Form of Establishment and Designation of Class A, Class B, Class C and Class Y Shares of Beneficial Interest	(i)
(1)(d)	Amendment to Agreement and Declaration of Trust Changing Name of Fund from “Pioneer Capital Growth Fund” to “Pioneer Mid-Cap Value Fund”	(ii)
(1)(e)	Amendment to Certificate of Trust Changing Name of Fund from “Pioneer Capital Growth Fund” to “Pioneer Mid-Cap Value Fund”	(ii)
(1)(f)	Amendment to Agreement and Declaration of Trust Changing Name of Fund from “Pioneer Mid-Cap Value Fund” to “Pioneer Mid Cap Value Fund”	(iii)
(1)(g)	Amendment to Certificate of Trust Changing Name of Fund from “Pioneer Mid-Cap Value Fund” to “Pioneer Mid Cap Value Fund”	(vii)
(2)	Amended and Restated By-Laws	(vii)
(3)	Not applicable
(4)	Form of Agreement and Plan of Reorganization	(x)
(5)	Not applicable
(6)(a)	Amended and Restated Management Agreement with Pioneer Investment Management, Inc.	(vii)
(6)(b)	Form of Expense Limitation Agreement	(viii)
(7)(a)	Underwriting Agreement with Pioneer Funds Distributor, Inc.	(iii)
(7)(b)	Dealer Sales Agreement	(vi)
(8)	Not applicable
(9)(a)	Custodian Agreement with Brown Brothers Harriman & Co.	(v)
(9)(b)	Amended Appendix A to Custodian Agreement	(vi)
(10)(a)	Distribution Plan pursuant to Rule 12b-1	(vii)
(10)(b)	Multiple Class Plan pursuant to Rule 18f-3	(iv)
(11)	Opinion of counsel as to the legality of the securities	(ix)

(12)	Opinion of counsel supporting tax matters and consequences to shareholders discussed in Part A of the Registration Statement on Form N-14	(*)
(13)(a)	Master Investment Company Service Agreement with Pioneer Investment Management Shareholder Services, Inc.	(v)
(13)(b)	Amended Exhibit A to Master Investment Company Service Agreement	(vi)
(13)(c)	Amended and Restated Administration Agreement with Pioneer Investment Management, Inc.	(vii)
(14)	Consents of Independent Registered Public Accounting Firms	(ix)
(15)	Not applicable
(16)	Power of Attorney	(viii)
(17)(a)	Pioneer Investment Management, Inc. and Pioneer Institutional Asset Management, Inc. Code of Ethics	(vii)
(17)(b)	Pioneer Funds Code of Ethics	(v)
(17)(c)	Pioneer Funds Distributor, Inc. Code of Ethics	(v)
(17)(d)	Form of Proxy Card	(viii)
(17)(e)	The Prospectus and Statement of Additional Information of Regions Morgan Keegan Select Mid Cap Value Fund dated April 1, 2008	(viii)
(17)(f)	The Annual Report of Regions Morgan Keegan Select Mid Cap Value Fund for the year ended November 30, 2008	(viii)
(17)(g)	The Prospectuses and Statement of Additional Information of the Registrant dated March 1, 2009	(ix)
(17)(h)	The Annual Report of the Registrant for the year ended October 31, 2008	(viii)

______________________________________

(i)	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 (the “SEC”) on June 30, 1998 (Accession No. 0001016964-98-000074).
(ii)	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 as filed with the SEC on February 28, 2000 (Accession No. 0001016964-00-000032).
(iii)	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 as filed with the SEC on March 1, 2002 (Accession No. 0001016964-02-000042).

(iv)	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 SEC on February 25, 2005 (Accession No. 0001016964-04-000076).
(v)	Previously filed. Incorporated herein by reference from the exhibits filed with Post-Effective Amendment No. 26 to the Registrant’s Registration Statement on Form N-1A (File No. 33-34801; 811-06106) as filed with the SEC on February 28, 2006 (Accession No. 0000869356-06-000014).
(vi)	Previously filed. Incorporated herein by reference from the exhibits filed with Post-Effective Amendment No. 27 to the Registrant’s Registration Statement on Form N-1A (File No. 33-34801; 811-06106) as filed with the SEC on February 27, 2007 (Accession No. 0000863334-07-000009).
(vii)	Previously filed. Incorporated herein by reference from the exhibits filed with Post-Effective Amendment No. 29 to the Registrant’s Registration Statement on Form N-1A (File No. 33-34801; 811-06106) as filed with the SEC on February 26, 2009 (Accession No. 0000863334-09-000004).
(viii)	Previously filed. Incorporated by reference from the exhibits filed with the Registrant’s Initial Registration Statement on Form N-14 (File No. 333-157312) as filed with the SEC on February 13, 2009 (Accession No. 0001145443-09-000143).
(ix)	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. 333-157312) as filed with the SEC on March 30, 2009 (Accession No. 0001145443-09-000655).
(x)	Previously filed. Attached as Exhibit A-2 to the combined Proxy Statement / Prospectus filed with Pre-Effective Amendment No. 1 to the Registrant's Registration Statement on Form N-14 (File No. 333-157312) as filed with the SEC on March 30, 2009 (Accession No. 0001145443-09-000655).
(*)	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 who is deemed to be an underwriter within the meaning of Rule 145(c) of the Securities Act of 1933, as amended (the “1933 Act”), 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 this Registration Statement and will not be used until the amendment is effective, and that, in determining any liability under the 1933 Act, 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)	Insofar as indemnification for liability arising under the 1933 Act 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 1933 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

   As required by the Securities Act of 1933, as amended, this Registration Statement has been signed on behalf of the Registrant, in the City of Boston and the Commonwealth of Massachusetts, on the 5th day of June 2009.

PIONEER MID CAP VALUE FUND

By: /s/ Mark E. Bradley

Name: Mark E. Bradley

Title: Chief Financial and Accounting Officer and Treasurer

(Principal Financial and Accounting Officer)

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

Signature	Title	Date
/s/ John F. Cogan, Jr.*	Chairman of the Board, Trustee and President	June 5, 2009
John F. Cogan, Jr.
/s/ Mark E. Bradley Mark E. Bradley	Chief Financial and Accounting Officer and Treasurer (Principal Financial and Accounting Officer)	June 5, 2009
/s/ Daniel K. Kingsbury*	Trustee and Executive Vice President	June 5, 2009
Daniel K. Kingsbury
/s/ David R. Bock*	Trustee	June 5, 2009
David R. Bock
/s/ Mary K. Bush*	Trustee	June 5, 2009
Mary K. Bush
/s/ Benjamin M. Friedman*	Trustee	June 5, 2009
Benjamin M. Friedman
/s/ Margaret B.W. Graham*	Trustee	June 5, 2009
Margaret B.W. Graham
/s/Thomas J. Perna*	Trustee	June 5, 2009
Thomas J. Perna
/s/ Marguerite A. Piret*	Trustee	June 5, 2009

Marguerite A. Piret
/s/ Stephen K. West*	Trustee	June 5, 2009
Stephen K. West

* By: /s/ Mark E. Bradley

Mark E. Bradley, Attorney-in-Fact

EXHIBIT INDEX

The following exhibit is filed as part of this Registration Statement:

Exhibit No. Description

    (12)                    Opinion of counsel supporting tax matters and consequences to shareholders

                                discussed in Part A of the Registration Statement on Form N-14

EX-8

EXHIBIT (12)

May 15, 2009

Regions Morgan Keegan Select Funds

50 North Front Street
Memphis, Tennessee 38103

Pioneer Mid Cap Value Fund

60 State Street

Boston, Massachusetts 02109

Ladies and Gentlemen:

This opinion is furnished to you pursuant to paragraph 8.5 of the Agreement and Plan of Reorganization, dated as of February 19, 2009 (the “Agreement”), by and between Pioneer Mid Cap Value Fund (the “Acquiring Trust”), a Delaware statutory trust, on behalf of Pioneer Mid Cap Value Fund, the sole series thereof (the “Acquiring Fund”), and Regions Morgan Keegan Select Funds (the “Acquired Trust”), a Massachusetts business trust, on behalf of Regions Morgan Keegan Select Mid Cap Value Fund, a series thereof (the “Acquired Fund”). All capitalized terms not otherwise defined herein have the meanings ascribed to them in the Agreement. The Agreement contemplates the acquisition of all of the assets of the Acquired Fund by the Acquiring Fund in exchange for (a) the assumption by the Acquiring Fund of the stated liabilities of the Acquired Fund and (b) the issuance and delivery by the Acquiring Fund to the Acquired Fund, for distribution, in accordance with Section 1.4 of the Agreement, pro rata within each class of Acquired Fund Shares, to the Acquired Fund Shareholders in exchange for their Acquired Fund Shares and in complete liquidation of the Acquired Fund, of a number of Acquiring Fund Shares of the corresponding class having an aggregate net asset value equal to the value of such assets, less the amount of such liabilities, of the Acquired Fund so transferred to the Acquiring Fund (the “Transaction”).

In connection with this opinion we have examined and relied upon the originals or copies, certified or otherwise identified to us to our satisfaction, of the Agreement, the Combined Proxy Statement and Prospectus on Form N-14 filed with the Securities and Exchange Commission on or about March 30, 2009 with respect to the Transaction, and related documents (collectively, the “Transaction Documents”). In that examination, we have assumed the genuineness of all signatures, the authenticity and completeness of all documents purporting to be originals (whether reviewed by us in original or

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May 15, 2009

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copy form) and the conformity to the originals of all documents purporting to be copies.

As to certain factual matters, we have relied with your consent upon, and our opinion is limited by, the representations of the various parties set forth in the Transaction Documents, and in certificates of the Acquired Trust and the Acquiring Trust dated as of the date hereof and attached hereto (the “Certificates”). Our opinion assumes (i) that all representations set forth in the Transaction Documents and in the Certificates will be true and correct in all material respects as of the date of the Transaction, and (ii) that the Agreement is implemented in accordance with its terms and consistent with the representations set forth in the Transaction Documents and Certificates. Our opinion is limited solely to the provisions of the Internal Revenue Code as presently in effect (the “Code”) and the regulations, rulings, and interpretations thereof in force as of this date. We assume no obligation to update our opinion to reflect any changes in law or in the interpretation thereof that may hereafter occur.

On the basis of and subject to the foregoing, we are of the opinion that, for United States federal income tax purposes:

1. The Reorganization will constitute a “reorganization” within the meaning of Section 368(a) of the Code, and the Acquiring Fund and the Acquired Fund will each be a “party to a reorganization” within the meaning of Section 368(b) of the Code.

2. No gain or loss will be recognized by the Acquired Fund upon the transfer of the Acquired Assets to the Acquiring Fund solely in exchange for Acquiring Fund Shares and the assumption by the Acquiring Fund of all of the Assumed Liabilities, or upon the distribution of the Acquiring Fund Shares by the Acquired Fund to its shareholders in liquidation, except for (A) any gain or loss that may be recognized on the transfer of “section 1256 contracts” as defined in Section 1256(b) of the Code, (B) any gain that may be recognized on the transfer of stock in a “passive foreign investment company” as defined in Section 1297(a) of the Code and (C) any other gain that may be required to be recognized as a result of the closing of the Acquired Fund’s tax year.

Regions Morgan Keegan Select Funds

Pioneer Mid Cap Value Fund

May 15, 2009

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3. The tax basis in the hands of the Acquiring Fund of each Acquired Asset so transferred will be the same as the tax basis of such Acquired Asset in the hands of the Acquired Fund immediately prior to the transfer, increased by the amount of gain (or decreased by the amount of loss), if any, recognized by the Acquired Fund upon the transfer.

4. The holding period of each Acquired Asset in the hands of the Acquiring Fund, other than assets, if any, with respect to which gain or loss is required to be recognized, will include in each instance the period during which the Acquired Asset was held by the Acquired Fund (except where investment activities of the Acquiring Fund have the effect of reducing or eliminating the holding period with respect to an asset).

5. No gain or loss will be recognized by the Acquiring Fund upon receipt of the Acquired Assets solely in exchange for Acquiring Fund Shares and the assumption by the Acquiring Fund of the Assumed Liabilities.

6. No gain or loss will be recognized by the Acquired Fund Shareholders upon the exchange of all of their Acquired Fund Shares solely for Acquiring Fund Shares as part of the Reorganization.

7. The aggregate basis of the Acquiring Fund Shares that an Acquired Fund Shareholder receives in the Reorganization will be the same as the aggregate basis of the Acquired Fund Shares exchanged therefor.

8. The holding period for the Acquiring Fund Shares received by each Acquired Fund Shareholder will include the holding period of the Acquired Fund Shares exchanged therefor, provided that such Acquired Fund Shares were held as capital assets on the date of the exchange.

Regions Morgan Keegan Select Funds

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May 15, 2009

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This opinion is being delivered solely to you for your use in connection with the referenced transaction, and may not be relied upon by any other person or used for any other purpose.

Very truly yours,

/s/ Bingham McCutchen LLP

BINGHAM MCCUTCHEN LLP