485BPOS

As filed with the Securities and Exchange Commission on August 29, 2013

File No. 333-187076

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. 2

(Check appropriate box or boxes)

PIONEER SERIES TRUST XI

(formerly, Pioneer 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)

Terrence J. Cullen, Secretary

Pioneer Investment Management, Inc.

60 State Street

Boston, Massachusetts 02109

(Name and Address of Agent for Service)

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.

Calculation of Registration Fee under the Securities Act of 1933: No filing fee is due because of reliance on Section 24(f) of the Investment Company Act of 1940, which permits registration of an indefinite number of securities.

Title of Securities Being Registered: Shares of beneficial interest of Pioneer Value Fund (now known as Pioneer Core Equity Fund), a series of the Registrant.

This filing will become effective on August 29, 2013, pursuant to Rule 485(b) under the Securities Act of 1933, as amended.

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Part A - Prospectus/Proxy Statement and Part B - Statement of Additional Information are incorporated by reference to Post-Effective Amendment No. 1 to the Registrant’s Registration Statement on Form N-14 as filed with the Securities and Exchange Commission on April 26, 2013.

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PART C

OTHER INFORMATION

PIONEER SERIES TRUST XI

ITEM 15. INDEMNIFICATION

No change from the information set forth in Item 30 of the most recently filed Registration Statement of Pioneer Series Trust XI (formerly, Pioneer Value Fund) (the "Registrant") on Form N-1A under the Securities Act of 1933 and the Investment Company Act of 1940 (File Nos. 2-32773 and 811-01835), as filed with the Securities and Exchange Commission on January 28, 2013 (Accession No. 0000078758-13-000004), which information is incorporated herein by reference.

ITEM 16. EXHIBITS

(1)(a)	Amended and Restated Agreement and Declaration of Trust	(6)
(1)(b)	Amendment to Amended and Restated Agreement and Declaration of Trust (as of May 22, 2010)	(8)
(1)(c)	Certificate of Trust	(1)
(1)(d)	Amended Certificate of Trust	(2)
(2)	Amended and Restated By-Laws	(6)
(3)	Not applicable
(4)	Form of Agreement and Plan of Reorganization	(*)
(5)	Reference is made to Exhibits (1) and (2) hereof
(6)(a)	Amended and Restated Management Agreement	(6)
(6)(b)	Expense Limit Agreement	(12)
(7)(a)	Underwriting Agreement	(2)
(7)(b)	Dealer Sales Agreement	(5)
(8)	Not applicable
(9)(a)	Custodian Agreement with Brown Brothers Harriman & Co.	(4)
(9)(b)	Amended Appendix A to Custodian Agreement (dated as of December 20, 2011)	(10)
(10)(a)	Pioneer Funds Distribution Plan	(6)
(10)(b)	Multiple Class Plan Pursuant to Rule 18f-3	(3)
(11)	Opinion of Counsel (legality of securities being offered)	(11)
(12)	Final opinion as to tax matters and consent	(**)
(13)(a)	Master Investment Company Service Agreement  with Pioneer Investment Management Shareholder Services, Inc.	(4)
(13)(b)	Amendment to Master Investment Company Service Agreement (May 5, 2007)	(5)
(13)(c)	Amendment No. 2 to Master Investment Company Service Agreement (January 16, 2009)	(7)
(13)(d)	Amendment No. 3 to Master Investment Company Service Agreement (March 5, 2010)	(8)
(13)(e)	Amendment No. 4 to Master Investment Company Service Agreement (March 8, 2011)	(9)
(13)(f)	Amendment No. 5 to Master Investment Company Service Agreement (December 1, 2011)	(10)
(13)(g)	Amended and Restated Administration Agreement (updated as of March 5, 2012)	(10)
(13)(h)	Administrative Agency Agreement, dated as of March 5, 2012, between Brown Brothers Harriman & Co. and Pioneer Investment Management, Inc.	(10)
(14)	Consent of Independent Registered Public Accounting Firm	(12)
(15)	Not applicable
(16)	Power of Attorney	(11)
(17)(a)	Code of Ethics of the Pioneer Funds, Pioneer Funds Distributor, Inc., Pioneer Institutional Asset Management, Inc., and Pioneer Investment Management, Inc.	(8)
(17)(b)	Prospectus of Pioneer Value Fund dated February 1, 2013, as supplemented, and Statement of Additional Information of Pioneer Value Fund dated February 1, 2013, as supplemented	(11)
(17)(c)	Annual Report of Pioneer Value Fund, for the fiscal year ended September 30, 2012	(11)
(17)(d)	Prospectus of Pioneer Research Fund dated May 1, 2012, as supplemented, and Statement of Additional Information of Pioneer Research Fund dated May 1, 2012, as supplemented	(11)
(17)(e)	Annual Report of Pioneer Research Fund for the fiscal year ended December 31, 2012	(11)

(1) Previously filed. Incorporated herein by reference from the exhibits filed with Post-Effective Amendment No. 46 to the Registrant’s Registration Statement on Form N-1A (File No. 2-32773) as filed with the Securities and Exchange Commission (the "SEC") on May 1, 1996 (Accession No. 0000078758-96-000017).

(2) Previously filed. Incorporated herein by reference from the exhibits filed with Post-Effective Amendment No. 56 to the Registrant's Registration Statement on Form N-1A (File No. 2-32773) as filed with the SEC on January 25, 2002 (Accession No. 0001016964-02-000006).

(3) Previously filed. Incorporated herein by reference from the exhibits filed with Registrant’s Initial Registration Statement on Form N-14 (File No. 333-118445), as filed with the Securities and Exchange Commission on August 20, 2004 (Accession No. 0001145443-04-001278).

(4) Previously filed. Incorporated herein by reference from the exhibits filed with Post-Effective Amendment No. 65 to the Registrant's Registration Statement on Form N-1A (File No. 2-32773) as filed with the SEC on January 27, 2006 (Accession No. 0001077452-06-000004).

(5) Previously filed. Incorporated herein by reference from the exhibits filed with Post-Effective Amendment No. 67 to the Registrant's Registration Statement on Form N-1A (File No. 2-32773) as filed with the SEC on January 28, 2008 (Accession No. 0000078758-08-000002).

(6) Previously filed. Incorporated herein by reference from the exhibits filed with Post-Effective Amendment No. 68 to the Registrant's Registration Statement on Form N-1A (File No. 2-32773) as filed with the SEC on January 28, 2009 (Accession No. 0000078758-09-000002).

(7) Previously filed. Incorporated herein by reference from the exhibits filed with Post-Effective Amendment No. 69 to the Registrant's Registration Statement on Form N-1A (File No. 2-32773) as filed with the SEC on November 20, 2009 (Accession No. 0000078758-09-000013).

(8) Previously filed.  Incorporated  herein by reference from the exhibits filed with Post-Effective  Amendment No. 71 to the  Registrant's Registration Statement on Form N-1A (File No. 2-32773)  as filed with the SEC on January 28, 2011 (Accession No. 0000078758-11-000002).

(9) Previously filed.  Incorporated  herein by reference from the exhibits filed with Post-Effective Amendment No. 73 to the Registrant's Registration Statement on Form N-1A (File No. 2-32773) as filed with the SEC on January 27, 2012 (Accession No. 0000078758-12-000002).

(10) Previously filed.  Incorporated herein by reference from the exhibits filed with Post-Effective Amendment No. 75 to the Registrant’s Registration Statement on Form N-1A (File No. 2-32773) as filed with the SEC on January 28, 2013 (Accession No. 0000078758-13-000004).

(11) Previously filed. Incorporated herein by reference from the exhibits filed with the Registrant’s Registration Statement on Form N-14 (File No. 333-187076) as filed with the SEC on March 6, 2013 (Accession No. 0000891804-13-000340).

(12) Previously filed. Incorporated herein by reference from the exhibits filed with Post-Effective Amendment No. 1 to the Registrant’s Registration Statement on Form N-14 (File No. 333-187076) as filed with the SEC on April 26, 2013 (Accession No. 0000891804-13-000559).

(*)   Attached as Exhibit A to the combined Information Statement/Prospectus

(**)  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) 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, the Registrant certifies that it meets all of the requirements for effectiveness of this Amendment to the Registration Statement on Form N-14 pursuant to rule 485(b) under the Securities Act of 1933, as amended, and has duly caused this Amendment to be signed on its behalf by the undersigned, thereunto duly authorized, in the City of Boston and the Commonwealth of Massachusetts, on the 29th day of August 2013.

PIONEER SERIES TRUST XI

By:              /s/ Daniel K. Kingsbury                                         

Name:  Daniel K. Kingsbury

Title:   Trustee and 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
/s/ John F. Cogan, Jr.* John F. Cogan, Jr	President (Principal Executive Officer) and Trustee	August 29, 2013
/s/ Mark E. Bradley Mark E. Bradley	Treasurer (Principal Financial and Accounting Officer)	August 29, 2013
/s/ David R. Bock* David R. Bock	Trustee	August 29, 2013
/s/ Benjamin M. Friedman* Benjamin M. Friedman	Trustee	August 29, 2013
/s/ Margaret B.W. Graham* Margaret B.W. Graham	Trustee	August 29, 2013
/s/ Daniel K. Kingsbury Daniel K. Kingsbury	Executive Vice President and Trustee	August 29, 2013
/s/ Thomas J. Perna* Thomas J. Perna	Chairman of the Board and Trustee	August 29, 2013
/s/ Marguerite A. Piret* Marguerite A. Piret	Trustee	August 29, 2013
/s/ Stephen K West* Stephen K. West	Trustee	August 29, 2013

* By:                            /s/ Daniel K. Kingsbury

                 Daniel K. Kingsbury, Attorney-in-Fact

EXHIBIT INDEX

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

Exhibit No.		Description
(12)	Final opinion as to tax matters and consent

EX-99.12 TAX OPINION

[Bingham McCutchen LLP Letterhead]

June 7, 2013

Pioneer Value Fund

60 State Street

Boston, Massachusetts 02109

Pioneer Research Fund

60 State Street

Boston, Massachusetts 02109

Ladies and Gentlemen:

This opinion is furnished to you pursuant to Paragraph 8.4 of the Agreement and Plan of Reorganization (the “Agreement”), dated as of June 7, 2013, by and between Pioneer Value Fund, a Delaware statutory trust, on behalf of Pioneer Value Fund, the sole series thereof, and Pioneer Research Fund, a Delaware statutory trust, on behalf of Pioneer Research Fund, the sole series thereof.  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 Pioneer Research Fund by Pioneer Value Fund in exchange for (a) the assumption by Pioneer Value Fund of the liabilities of Pioneer Research Fund and (b) the issuance and delivery by Pioneer Value Fund to Pioneer Research Fund, for distribution, in accordance with Paragraph 1.4 of the Agreement, pro rata to Research Fund Shareholders in exchange for their Research Fund Shares and in complete liquidation of Pioneer Research Fund, of a number of Value Fund Shares having an aggregate net asset value equal to the value of such assets, less the amount of such liabilities, of Pioneer Research Fund so transferred to Pioneer Value 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 and related documents (collectively, the “Transaction Documents”).  In that examination, we have assumed the genuineness of all signatures, the capacity and authority of each party executing a document to so execute the document, the authenticity and completeness of all documents purporting to be originals (whether reviewed by us in original or copy form) and the conformity to the originals of all documents purporting to be copies.  We have also assumed that each agreement and other instrument reviewed by us is valid and binding on the party or parties thereto and is enforceable in accordance with its terms, and that there are no contracts, agreements, arrangements, or understandings, either written or oral, that are inconsistent with or that would materially alter the terms of the Agreement or the other Transaction Documents.

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 Pioneer Value Fund and Pioneer Research Fund, each

Pioneer Value Fund

Pioneer Research Fund

June 7, 2013

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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 of 1986, as amended and 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 transfer to Pioneer Value Fund of all of the assets of Pioneer Research Fund in exchange solely for the issuance of Value Fund Shares to Pioneer Research Fund and the assumption by Pioneer Value Fund of all of the liabilities of Pioneer Research Fund, followed by the distribution of such Value Fund Shares to the shareholders of Pioneer Research Fund in complete liquidation of Pioneer Research Fund will constitute a “reorganization” within the meaning of Section 368(a) of the Code, and Pioneer Value Fund and Pioneer Research 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 Pioneer Research Fund upon the transfer of Pioneer Research Fund’s assets to Pioneer Value Fund solely in exchange for Value Fund Shares and the assumption by Pioneer Value Fund of all of the liabilities of Pioneer Research Fund, or upon the distribution of the Value Fund Shares by Pioneer Research 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 Pioneer Research Fund’s taxable year or upon the transfer of a Research Fund Asset regardless of whether such transfer would otherwise be a nonrecognition transaction under the Code.

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

Pioneer Value Fund

Pioneer Research Fund

June 7, 2013

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4.   The holding period of each asset so transferred in the hands of Pioneer Value Fund, other than any asset with respect to which gain or loss is required to be recognized, will include in each instance the period during which such asset was held by Pioneer Research Fund (except where investment activities of Pioneer Value 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 Pioneer Value Fund upon receipt of the assets solely in exchange for Value Fund Shares and the assumption by Pioneer Value Fund of the liabilities of Pioneer Research Fund.

6.   No gain or loss will be recognized by Research Fund Shareholders upon the exchange of all of their Research Fund Shares solely for Value Fund Shares as part of the Transaction.

7.   The aggregate tax basis of Value Fund Shares that each Research Fund Shareholder receives in the Transaction will be the same as the aggregate tax basis of the Research Fund Shares exchanged therefor.

8.   Each Research Fund Shareholder’s holding period for the Value Fund Shares received in the Transaction will include the holding period of the Research Fund Shares exchanged therefor, provided that the Research Fund Shareholder held such Research Fund Shares as capital assets on the date of the exchange.

This opinion is being delivered solely to you for your use in connection with the referenced Transaction.  It is intended solely for the benefit of you and the Research Fund Shareholders 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