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):  June 30, 2010

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):

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

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

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

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

ITEM 8.01             Other Events.

On June 30, 2010, Affiliated Managers Group, Inc. (“AMG”) completed its previously announced acquisition of Pantheon Ventures Inc., Pantheon Capital (Asia) Limited, and Pantheon Holdings Limited and Subsidiaries (collectively, “Pantheon”), as described in the Current Report on Form 8-K filed on July 1, 2010.  Attached hereto are historical financial statements for Pantheon and unaudited pro forma financial information giving effect to the acquisition.

ITEM 9.01             Financial Statements and Exhibits.

(a)          Financial Statements of Business Acquired.

1.               The audited combined financial statements of Pantheon Ventures Inc., Pantheon Capital (Asia) Limited, and Pantheon Holdings Limited and Subsidiaries as of and for the years ended December 31, 2009 and 2008 are filed as Exhibit 99.1 hereto.

2.               The unaudited condensed combined financial statements of Pantheon Ventures Inc., Pantheon Capital (Asia) Limited, and Pantheon Holdings Limited and Subsidiaries as of and for the three months ended March 31, 2010, are filed as Exhibit 99.2 hereto.

(b)         Pro Forma Financial Information.

1.               The unaudited pro forma condensed combined financial information of AMG, reflecting the acquisition of Pantheon, as of and for the three months ended March 31, 2010, and the year ended December 31, 2009, is filed as Exhibit 99.3 hereto.

(d)         Exhibits.

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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

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Exhibit 23.1

CONSENT OF INDEPENDENT ACCOUNTANTS

We hereby consent to the incorporation by reference in the Registration Statement on Forms S-3 (File No. 333-148030 and File No. 333-148029), and S-8 (File No. 333-135416, File No. 333-129748, File No. 333-100628, File No. 333-84485, and File No. 333-72967) of Affiliated Managers Group, Inc. of our report dated February 26, 2010 relating to the combined financial statements of Pantheon Ventures Inc., Pantheon Capital (Asia) Limited, and Pantheon Holdings Limited and Subsidiaries, which appears in this Current Report on Form 8-K of Affiliated Managers Group, Inc. dated August 6, 2010.

/s/ PricewaterhouseCoopers LLP

Seattle, Washington

August 6, 2010

Exhibit 99.1

Report of Independent Auditors

To the Board of Directors and Stockholders of

Frank Russell Company and Subsidiaries

In our opinion, the accompanying combined balance sheets and the related combined statements of income, changes in stockholder’s equity and comprehensive income and cash flows present fairly, in all material respects, the combined financial position of Pantheon Ventures Inc., Pantheon Capital (Asia) Limited, and Pantheon Holdings Limited and subsidiaries (collectively the “Company”) at December 31, 2009 and 2008, and the results of their operations and their cash flows for the years then ended in conformity with accounting principles generally accepted in the United States of America.  These combined financial statements are the responsibility of the Company’s management.  Our responsibility is to express an opinion on these combined financial statements based on our audits.  We conducted our audits of these statements in accordance with auditing standards generally accepted in the United States of America.  Those standards require that we plan and perform the audit to obtain reasonable assurance about whether the financial statements are free of material misstatement.  An audit includes examining, on a test basis, evidence supporting the amounts and disclosures in the financial statements, assessing the accounting principles used and significant estimates made by management, and evaluating the overall financial statement presentation.  We believe that our audits provide a reasonable basis for our opinion.

As discussed in Note 5 to the combined financial statements, the Company changed the manner in which it accounts for uncertain tax positions in 2009.

/s/ PricewaterhouseCoopers LLP

Seattle, Washington

February 26, 2010

Pantheon Ventures Inc., Pantheon Capital (Asia) Limited, and

Pantheon Holdings Limited and Subsidiaries

Combined Balance Sheets

December 31, 2009 and 2008

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

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Pantheon Ventures Inc., Pantheon Capital (Asia) Limited, and
Pantheon Holdings Limited and Subsidiaries

Combined Statements of Income

Years Ended December 31, 2009 and 2008

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

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Pantheon Ventures Inc., Pantheon Capital (Asia) Limited, and Pantheon Holdings Limited and Subsidiaries

Combined Statements of Changes in Stockholder’s Equity and Comprehensive Income

Years Ended December 31, 2009 and 2008

(dollars in thousands)

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

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Pantheon Ventures Inc., Pantheon Capital (Asia) Limited, and Pantheon Holdings Limited and Subsidiaries

Combined Statements of Changes in Stockholder’s Equity and Comprehensive Income

Years Ended December 31, 2009 and 2008

(dollars in thousands)

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

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Pantheon Ventures Inc., Pantheon Capital (Asia) Limited, and Pantheon Holdings Limited and Subsidiaries

Combined Statements of Cash Flows

Years Ended December 31, 2009 and 2008

(dollars in thousands)

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

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Pantheon Ventures Inc., Pantheon Capital (Asia) Limited, and Pantheon Holdings Limited and Subsidiaries

Notes to Combined Financial Statements

December 31, 2009 and 2008

1.                            Nature of Business and Significant Accounting Policies

Nature of Business

Pantheon Ventures Inc., Pantheon Capital (Asia) Limited, and Pantheon Holdings Limited and subsidiaries (collectively the “Company”) are wholly-owned subsidiaries of Frank Russell Company (“Russell”). The Northwestern Mutual Life Insurance Company (“NML”) owns substantially all of the outstanding shares of Russell.

Pantheon Ventures Inc. is an investment advisor registered pursuant to the Investment Advisors Act of 1940, which provides investment management services to various domestic and international entities.

Pantheon Capital (Asia) Limited is a registered investment advisor that provides investment advice on securities under the Hong Kong Securities and Futures Ordinance.  Its principal activity is advising on securities to its overseas associated companies and their respective institutional clients.

Pantheon Holdings Limited and subsidiaries is a UK based holding company with subsidiaries that provide investment management services, predominantly in connection with unregistered investment companies.

On February 10, 2010, Russell accepted the offer of Affiliated Managers Group, Inc. (“AMG”) to purchase certain legal entities and assets and liabilities of the Company (the “Transaction”).

The Company had no separate legal status and historically did not prepare combined financial statements. The combined historical financial information included herein was prepared specifically for the purpose of facilitating the Transaction and includes the historical basis in assets and liabilities and the historical results of operations of each of the entities constituting the Company as of December 31, 2009 and 2008 and for each of the two years in the period ended December 31, 2009.

The combined financial statements include all historical assets, liabilities, results of operations, and cash flows of the entities included in the Transaction, and those of their consolidated subsidiaries, even if certain of those assets, liabilities and consolidated subsidiaries of included entities have been excluded from the Transaction.

The combined financial information included herein may not necessarily be indicative of the Company’s results of operations, financial condition and cash flows in the future or what its results of operations, financial condition and cash flows would have been had the Company been a stand-alone company during the periods presented.

Principles of Combination

The accompanying combined financial statements are presented in accordance with accounting principles generally accepted in the U.S. (“GAAP”) and include the accounts of the Company and its wholly owned subsidiaries.   Transactions and balances between entities included within these combined financial statements have been eliminated. Transactions and balances between the Company and Russell and its subsidiaries have been separately identified as related-party transactions. See Note 9, Related Party Transactions.

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Pantheon Ventures Inc., Pantheon Capital (Asia) Limited, and Pantheon Holdings Limited and Subsidiaries

Notes to Combined Financial Statements

December 31, 2009 and 2008

The combined statements of income include allocations of certain costs from Russell directly related to the operations of the Company, including an apportionment of central general and administrative costs for accounting, human resources, information systems and other overhead costs.  These centralized costs were allocated to the Company based on the Company’s analysis of its historical costs used to develop the Transition Agreement (as further discussed in Note 11) or actual costs incurred or employee headcount.  Management believes the methodologies applied for the allocation of these costs is reasonable.

Use of Estimates

The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent liabilities at the date of the combined financial statements and the reported amounts of revenues and expenses during the reporting period.  Significant estimates are inherent in the preparation of the financial statements.  Actual results could materially differ from those estimates.

Cash and Cash Equivalents

The Company considers all money market funds and instruments with maturities of three months or less at the purchase date as cash equivalents.

Fixed Assets

Fixed assets are reported at cost less accumulated depreciation.  Depreciation is calculated using the straight-line method based on estimated useful lives ranging from three to 15 years.  Equipment and office furniture are depreciated over estimated useful lives ranging from three to seven years.  Capitalized software includes purchased and internally developed software.  Purchased software is amortized over three years using the straight-line method.  Internally developed software represents internal and external costs incurred to develop internal use software during the application development stage.  Once the internal use software is ready for its intended use, the accumulated development costs are amortized over three years using the straight-line method.  Leasehold improvements are amortized over the shorter of their estimated useful lives or the remaining life of the lease.  Amortization of those assets recorded under capital lease agreements is included in depreciation expense.  When fixed assets are sold or otherwise disposed of, the cost and related accumulated depreciation are removed from the respective accounts and any resulting gains or losses are included in income from operations.  Repair and maintenance costs are expensed as incurred.

Investments

Equity method investees and cost method investees are comprised primarily of investments in affiliated private equity investment funds (“Investment Funds”).

Investments in which the Company has significant influence, but less than a controlling interest and do not meet the other criteria for consolidation in accordance with GAAP, are accounted for using the equity method of accounting.  The Company’s investment in equity method investees is included in investments in the combined balance sheets.  The Company’s share of each investee’s earnings (losses) is included in earnings in equity method investees in the combined statements of income.  Dividends or cash distributions, as well as additional cash investments or other cash paid to the investee, are included in the combined statement of cash flows.

Investments in which the Company does not have a controlling interest or significant influence are accounted for using the cost method of accounting.  Under the cost method, the Investment Funds are accounted for in the combined balance sheets at original cost and dividends are included in

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Pantheon Ventures Inc., Pantheon Capital (Asia) Limited, and Pantheon Holdings Limited and Subsidiaries

Notes to Combined Financial Statements

December 31, 2009 and 2008

earnings when declared.  When a decline in fair value of an investment carried at cost is determined to be other-than-temporary, the investment is written down to fair value and the loss is included in the determination of earnings.

A component of the valuation of the Investment Funds is the performance-based incentive fee (“Carry”) payable to the general partner and, in some instances, other specified parties.  Certain Investment Funds also receive Carry from the Underlying Investments (as defined below) which they record.  In certain instances, Carry is not finalized until a contractual end date that extends beyond the reporting period.  It is the Company’s policy in valuing its holdings in Investment Funds, to not record incentive fees until the end of the contract period when the payment of fees is assured.

Investments made by Investment Funds (the “Underlying Investments”) generally consist of illiquid investments that are carried at fair value.  Fair value of the Underlying Investments has been determined by the general partner of each respective Investment Fund in good faith to reflect the fair value of the Company’s capital account balance.  Depending on the facts and circumstances, the Company considers potential valuation adjustments, if any.  Accordingly, valuations do not necessarily represent the amounts that might be realized from sales or other dispositions of Underlying Investments, nor do they reflect taxes or other expenses that might be incurred upon disposition.  Because of the inherent uncertainty of valuations of certain Underlying Investments, the estimated values for the Company’s investments in those Investment Funds may differ significantly from the values that would have been used had a ready market existed.

The Company’s investment transactions are recorded on the trade date, which is defined as the date the Company obtains an enforceable right to demand the securities or payment.  Realized gains and losses on investments sold are computed on a specific identification basis.  Interest income and expenses are recorded on the accrual basis.  Distributions from Investment Funds are recorded as declared and classified as either income or realized gain as disclosed to the partnership by management of the respective entity.

Goodwill and Intangible Assets

Goodwill and indefinite-lived intangible assets are not amortized, but are tested for impairment on an annual basis, and between annual tests if circumstances would reduce the fair value of a reporting unit below its carrying value, and written down if impaired.  The fair value of each reporting unit is estimated using both an income approach and a market approach.  If the carrying amount of a reporting unit exceeds its fair value, the second step of the goodwill impairment test is performed to measure the amount of impairment loss, if any.  The second step of the goodwill impairment test compares the implied fair value of the reporting unit’s goodwill with the carrying value of that goodwill.  If the carrying amount of the reporting unit’s goodwill exceeds the implied fair value of that goodwill, an impairment loss is recognized in an amount equal to that excess.  The income approach and the market approach require significant assumptions to determine the fair value of each reporting unit.  The significant assumptions used in the income approach and the market approach include estimates of our future revenues, cash flow information, fair value indicators, operating plans, industry data and other relevant factors.  The Company performed an evaluation of the carrying value as of December 31, 2009 and 2008 and concluded that there was no impairment of goodwill or indefinite-lived intangibles.

The Company has capitalized the value of client and fund relationships, acquired technology, and a trade name obtained through acquisition.  Client and fund relationships are amortized using the straight-line method based upon an estimated useful life of 15 years.  Acquired technology is

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Pantheon Ventures Inc., Pantheon Capital (Asia) Limited, and Pantheon Holdings Limited and Subsidiaries

Notes to Combined Financial Statements

December 31, 2009 and 2008

amortized over an estimated useful life of three years using the straight-line method.  The acquired Pantheon trade name is an intangible asset determined to have an indefinite useful life and is not amortized.

Impairment of Long-lived Assets

The Company assesses the impairment of long-lived assets, including indefinite life intangible assets, whenever events or changes in business circumstances indicate that the carrying amount of an asset may not be recoverable.  When such events occur, management determines whether there has been an impairment by comparing the anticipated undiscounted net future cash flows to the related asset’s carrying value.  If an impairment exists, the asset is written down to its estimated fair value.  The Company did not record any impairment losses related to long-lived assets during the periods presented.

Revenue Recognition

Revenue is generated through investment management fees earned for managing investment limited partnerships and separate account clients and is recognized as earned based on the underlying nature of the respective management agreements.  The Company also receives performance-based incentive fees (“Carry”) in accordance with the terms stated in individual management agreements.  It is the Company’s policy to not record performance-based incentive fees until the end of the contract period when the payment of fees is assured.

Accounts are deemed past due based on payment terms.  The Company writes off delinquent accounts to the extent and at the time they are deemed to not be recoverable.  The Company has not recorded any bad debt expense for the years ended December 31, 2009 and 2008.

Income Taxes

Deferred income tax assets and liabilities are determined based upon differences between the financial statement and income tax bases of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse.  The realization of deferred tax assets is based on historical tax positions and estimates of future taxable income.  The Company evaluates both the positive and negative evidence that it believes is relevant in assessing whether it will realize the deferred tax assets.  A valuation allowance is recorded when it is more likely than not that some of the deferred tax assets will not be realized.

The Company files its federal tax return with Russell, who files its federal tax return with Northwestern Mutual Life Insurance Company as part of a consolidated group.  The Company files a tax return, either on a separate return basis, or as part of Russell’s unitary or combined group, in certain states.  The provision for federal and state income taxes is based on an allocation of the consolidated tax liability to the respective companies included in the consolidated group as if each company were filing on a separate return basis.  Federal taxes payable are recorded through and included in due to affiliates while state income taxes payable are included in accrued expenses in the accompanying combined balance sheets.

Effective January 1, 2009, the Company adopted the authoritative guidance under GAAP for accounting and reporting uncertainty in income taxes.  This guidance clarifies how and when uncertain tax positions are to be recognized and disclosed in the financial statements.  The impact of adopting this guidance is reflected in Note 5.

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Pantheon Ventures Inc., Pantheon Capital (Asia) Limited, and Pantheon Holdings Limited and Subsidiaries

Notes to Combined Financial Statements

December 31, 2009 and 2008

Foreign Currency

An entity’s functional currency is determined by the currency of the economic environment in which the majority of cash is generated and expended by the entity.  The financial statements of all subsidiaries with a functional currency other than the U.S. dollar have been translated into the Company’s reporting currency, the U.S. dollar in accordance with GAAP. All assets and liabilities of the respective entities are translated at year-end exchange rates and all revenues and expenses are translated at average month exchange rates during the respective period.  Translation adjustments are reported as a separate component of accumulated other comprehensive income in equity.

Foreign currency transaction gains and losses are a result of the effect of exchange rate changes on transactions denominated in currencies other than the functional currency, including U.S. dollars.  Gains and losses on those foreign currency transactions are included in determining net income or loss for the period as a component of other income (expense).

Stock-Based Compensation

Russell has a Long-term Equity-Based Incentive Plan (“LTIP”) and callable puttable common stock issued under the Incentive Payment Plan (“IPP”) covering eligible employees of the Company as more fully described in Note 6.  Equity-classified awards are measured at fair value as of the grant dates or modification dates and the resulting cost is recognized over the period from the date of grant to the date when the award is no longer contingent upon the employee providing additional service (the required service period).  For awards that vest upon retirement, the required service period does not extend beyond the date an employee is eligible for retirement.  This situation can result in compensation expense being recognized over a period less than the stated vesting period.  Liability-classified awards are remeasured to fair value at each balance sheet date until the award is settled.

Deferred Incentive Compensation

Russell has granted award units under the IPP and under the Incentive Share Plan (“ISP”), more fully described in Note 6.  The Company accounts for these deferred incentive arrangements, which are not share-based, using an accelerated method of attribution of the related expense.

New Accounting Pronouncements

In May 2009, the Financial Accounting Standards Board (“FASB”) issued authoritative guidance under GAAP, which establishes general standards of accounting for and disclosure of events that occur after the balance sheet date but before the financial statements are issued or are available to be issued. It requires the disclosure of the date through which an entity has evaluated subsequent events and the basis for that date.  The authoritative guidance is effective for annual reporting periods ending after June 15, 2009, and shall be applied prospectively. The Company’s adoption of this standard did not have an effect on the Company’s combined financial position, results of operations, or cash flows.

In June 2009, the FASB issued authoritative guidance codifying Accounting Standards and the Hierarchy of GAAP (the “Codification”). The Codification is the source of authoritative accounting principles to be applied in the preparation of financial statements in conformity with GAAP. All existing accounting standards are superseded. All other accounting guidance not included in the Codification will be considered non-authoritative. The Codification is effective for annual periods ending after September 15, 2009. The adoption of the Codification does not impact the Company’s combined financial statements except for references made to authoritative accounting literature in the footnotes.

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Pantheon Ventures Inc., Pantheon Capital (Asia) Limited, and

Pantheon Holdings Limited and Subsidiaries

Notes to Combined Financial Statements

December 31, 2009 and 2008

In June 2009, the FASB issued amended guidance related to the consolidation of variable-interest entities. The key amendments include (1) the elimination of the exemption for qualifying special purpose entities, (2) a new approach for determining who should consolidate a variable-interest entity, and (3) changes to when it is necessary to reassess who should consolidate a variable-interest entity.  This guidance will be effective for financial statements issued for fiscal years beginning after November 15, 2009. In January 2010, the FASB announced a deferral of this guidance for certain investment entities.  The deferral allows asset managers that have no obligation to fund potentially significant losses of an investment entity to continue to apply the previous accounting guidance to investment entities that have the attributes of entities subject to ASC 946 (the “investment company guide”).  The Company is in the process of evaluating the impact that the adoption of this guidance will have on its combined financial position, results of operations and cash flows.

In June 2009, the FASB issued guidance on transfers and servicing of financial assets to eliminate the concept of a qualifying special-purpose entity, change the requirements for off balance sheet accounting for financial assets including limiting the circumstances where off balance sheet treatment for a portion of a financial asset is allowable, and require additional disclosures. The guidance is effective for the Company’s 2011 fiscal year. The Company does not expect that the adoption of this guidance will have a material impact on its combined financial position, results of operations and cash flows.

2.                                      Fixed Assets

Fixed assets, net, consist of the following at December 31:

Depreciation and amortization expense related to fixed assets was $1.2 million and $1.3 million for the years ended December 31, 2009 and 2008, respectively.

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Pantheon Ventures Inc., Pantheon Capital (Asia) Limited, and

Pantheon Holdings Limited and Subsidiaries

Notes to Combined Financial Statements

December 31, 2009 and 2008

3.                                      Investments

All of the Company’s investments in equity method investees represent investments in affiliated funds. For cost method investments, the carrying value is equivalent to historical cost.  There have been no identified events or changes in circumstances that may have a significant adverse effect on the recoverability of the recorded investment value. Investments consist of the following at December 31:

The Company is a variable interest holder in variable interest entities (“VIEs”) which are not consolidated, as the Company is not the primary beneficiary.  These VIEs represent certain private equity funds of funds.  Net assets of these entities total approximately $483.4 million and $487.1 million as of December 31, 2009 and 2008, respectively.  The Company’s aggregate maximum exposure to loss is limited to its investment balances in these entities, which is approximately $0.3 million and $0.4 million as of December 31, 2009 and 2008, respectively.  The Company’s involvement with these entities began on the dates that the entities were formed.

4.                                      Goodwill and Intangible Assets

The change in goodwill from December 31, 2008 to December 31, 2009 of $5.6 million is due to changes in the functional currency other than the U.S. dollar.

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Pantheon Ventures Inc., Pantheon Capital (Asia) Limited, and

Pantheon Holdings Limited and Subsidiaries

Notes to Combined Financial Statements

December 31, 2009 and 2008

Intangible assets consist of the following at December 31:

Amortization expense related to intangible assets was $5.6 million and $5.9 million for the years ended December 31, 2009 and 2008, respectively.  Expected amortization expense for each of the succeeding five years is as follows:

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Pantheon Ventures Inc., Pantheon Capital (Asia) Limited, and

Pantheon Holdings Limited and Subsidiaries

Notes to Combined Financial Statements

December 31, 2009 and 2008

5.                                      Income Taxes

Income tax expense consists of the following amounts for the year ended December 31:

A reconciliation of the statutory U.S. federal income tax rate to the Company’s effective income tax rate is as follows for the year ended December 31: