UNITED STATES
SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, DC 20549

FORM 8-K

CURRENT REPORT PURSUANT
TO SECTION 13 OR 15(D) OF THE
SECURITIES EXCHANGE ACT OF 1934

Date of report (Date of earliest event reported)          December 14, 2006

Affiliated Managers Group, Inc.

(Exact Name of Registrant as Specified in Its Charter)

Delaware

(State or Other Jurisdiction of Incorporation)

(617) 747-3300

(Registrant’s Telephone Number, Including Area Code)

N/A

(Former Name or Former Address, if Changed Since Last Report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions ( see General Instruction A.2. below):

o            Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

o            Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

o            Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

o            Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

ITEM 7.01         Regulation FD Disclosure.

On December 22, 2006, Affiliated Managers Group, Inc. (the “Company”) announced that it had completed its previously announced acquisition of Chicago Equity Partners, LLC.  A copy of the press release announcing the closing of the transaction is furnished as Exhibit 99.1 hereto and is incorporated by reference.

ITEM 8.01         Other Events.

On December 14, 2006, the Company announced the appointment of Nathaniel Dalton as Chief Operating Officer. A copy of the press release announcing this appointment is furnished as Exhibit 99.2 hereto and is incorporated by reference.

ITEM 9.01         Financial Statements and Exhibits.

(c)   Exhibits.

*                    This exhibit shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, or otherwise subject to the liability of that section, nor shall it be incorporated by reference into any filing under the Securities Act of 1933 or the Securities Exchange Act of 1934.

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SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

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EXHIBIT INDEX

*                    This exhibit shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, or otherwise subject to the liability of that section, nor shall it be incorporated by reference into any filing under the Securities Act of 1933 or the Securities Exchange Act of 1934.

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Exhibit 99.1

AMG Completes Investment in Chicago Equity Partners

Boston, MA, December 22, 2006 —Affiliated Managers Group, Inc. (NYSE: AMG), an asset management company, today announced the completion of its acquisition of a majority equity interest in Chicago Equity Partners, LLC (“CEP”).

CEP, a highly regarded institutional money manager with approximately $12.0 billion in assets under management, uses a proven, systematic investment process and offers a broad range of domestic equity and fixed income products.  The firm has a solid performance record, generating compound annual growth in assets under management of 27% since 2002, including over $3 billion in net client cash flows.

CEP’s client base includes over 120 institutional investors, including public funds, corporations, endowments and foundations, Taft-Hartley plan sponsors and certain mutual fund advisers.

At the closing of the transaction, AMG purchased approximately a 60% interest in CEP. The remaining interest, approximately 40% of the business, is held by nine key CEP professionals, including the five founding partners, who continue to manage the firm’s day-to-day operations.

AMG is an asset management company with equity investments in a diverse group of mid-sized investment management firms. AMG’s strategy is to generate growth through the internal growth of its existing Affiliates, as well as through investments in new Affiliates. AMG’s innovative transaction structure allows individual members of each Affiliate’s management team to retain or receive significant direct equity ownership in their firm while maintaining operating autonomy. In addition, AMG provides centralized assistance to its Affiliates in strategic matters, marketing, distribution, product development and operations. Pro forma for its investment in CEP, AMG’s affiliated investment management firms managed approximately $222 billion in assets at September 30, 2006.

Certain matters discussed in this press release may constitute forward-looking statements within the meaning of the federal securities laws.  Actual results and the timing of certain events could differ materially from those projected in or contemplated by the forward-looking statements due to a number of factors, including changes in the securities or financial markets or in general economic conditions, the availability of equity and debt financing, competition for acquisitions of interests in investment management firms, our ability to complete pending acquisitions, the investment performance of our Affiliates and their ability to effectively market their investment strategies, and other risks detailed from time to time in AMG’s filings with the Securities and Exchange Commission.  Reference is hereby made to the “Cautionary Statements” set forth in the Company’s Form 10-K for the year ended December 31, 2005.

For more information on Affiliated Managers Group, Inc.,
please visit AMG’s Web site at www.amg.com.

Exhibit 99.2

AMG Names Nathaniel Dalton as Chief Operating Officer

Boston, MA, December 14, 2006 — Sean M. Healey, President and Chief Executive Officer of Affiliated Managers Group, Inc. (NYSE: AMG), today announced the appointment of Nathaniel Dalton as Executive Vice President and Chief Operating Officer.

“The AMG business model has an established reputation for delivering outstanding growth and excellent investment returns for our shareholders,” said Mr. Healey.  “Nate has played a key role in maintaining strong relationships with our Affiliate partners and identifying opportunities to develop and grow their businesses.”

Since the beginning of 2004, AMG Affiliates have generated organic growth of $70 billion, or 80%, through outstanding investment performance and strong net client cash flows.

Mr. Healey added, “Our operating momentum has never been stronger, and we look to Nate’s leadership and broad experience as Chief Operating Officer to execute initiatives that enhance our growth and profitability.”

Mr. Dalton, age 40, joined AMG in 1996 as Senior Vice President and General Counsel, and became Executive Vice President responsible for the Company’s Affiliate Development efforts in 2001.

“AMG has a remarkable management team and we have successfully leveraged our core strengths to generate excellent results across our business,” said Mr. Dalton.  “I have enjoyed close relationships with our Affiliate partners, and we look forward to continuing to position AMG for growth in 2007 and beyond.”

In addition, Mr. Dalton served as General Counsel and as the Company’s Secretary until June 2002. Prior to joining AMG, he was an attorney at Goodwin Procter LLP, focusing on mergers and acquisitions. He received a J.D. from Boston University School of Law and a B.A. from the University of Pennsylvania.  Mr. Dalton resides in Swampscott, Massachusetts, with his wife and two children.

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AMG Names Nathaniel Dalton as Chief Operating Officer
December 14, 2006
Page 2 of 2

AMG is an asset management company with equity investments in a diverse group of mid-sized investment management firms. AMG’s strategy is to generate growth through the internal growth of its existing Affiliates, as well as through investments in new Affiliates. AMG’s innovative transaction structure allows individual members of each Affiliate’s management team to retain or receive significant direct equity ownership in their firm while maintaining operating autonomy. In addition, AMG provides centralized assistance to its Affiliates in strategic matters, marketing, distribution, product development and operations. Pro forma for its pending investment in Chicago Equity Partners, AMG’s affiliated investment management firms managed $222 billion in assets at September 30, 2006.

Certain matters discussed in this press release may constitute forward-looking statements within the meaning of the federal securities laws.  Actual results and the timing of certain events could differ materially from those projected in or contemplated by the forward-looking statements due to a number of factors, including changes in the securities or financial markets or in general economic conditions, the availability of equity and debt financing, competition for acquisitions of interests in investment management firms, our ability to complete pending acquisitions, the investment performance of our Affiliates and their ability to effectively market their investment strategies, and other risks detailed from time to time in AMG’s filings with the Securities and Exchange Commission.  Reference is hereby made to the “Cautionary Statements” set forth in the Company’s Form 10-K for the year ended December 31, 2005.

For more information on Affiliated Managers Group, Inc.,
please visit AMG’s Web site at www.amg.com.