SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

FORM 10-Q

Quarterly Report Pursuant to Section 13 or 15(d)

of the Securities Exchange Act of 1934

For the quarterly period ended SeptemberJune 30, 20092010

Marsh & McLennan Companies, Inc.

1166 Avenue of the Americas

New York, New York 10036

(212) 345-5000

Commission file number 1-5998

State of Incorporation: Delaware

I.R.S. Employer Identification No. 36-2668272

Indicate by check mark whether the registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days.    Yes  x    No  ¨

Indicate by check mark whether the registrant has submitted electronically and posted on its corporate Website, if any, every Interactive Data File required to be submitted and posted pursuant to Rule 405 of Regulation S-T during the preceding 12 months (or for such shorter period that the registrant was required to submit and post such files).    Yes  x    No  ¨

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer or a smaller reporting company. See the definitions of “large accelerated filer,” “accelerated filer” and “smaller reporting company” in Rule 12b-2 of the Exchange Act. (Check one):

Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Exchange Act).    Yes  ¨    No  x

As of OctoberJuly 31, 2009,2010, there were outstanding 527,513,131542,474,395 shares of common stock, par value $1.00 per share, of the registrant.

INFORMATION CONCERNING FORWARD-LOOKING STATEMENTS

This Quarterly Report on Form 10-Q contains “forward-looking statements,” as defined in the Private Securities Litigation Reform Act of 1995. These statements, which express management’s current views concerning future events or results, use words like “anticipate,” “assume,” “believe,” “continue,” “estimate,” “expect,” “intend,” “plan,” “project” and similar terms, and future or conditional tense verbs like “could,” “may,” “might,” “should,” “will” and “would.” For example, we may use forward-looking statements when addressing topics such as: the outcome of contingencies; market and industry conditions, including competitive and pricing trends;conditions; changes in our business strategies and methods of generating revenue; the development and performance of our services and products; changes in the composition or level of MMC’s revenues; our cost structure and the outcome of cost-saving or restructuring initiatives; the outcome of contingencies; dividend policy; the expected impact of acquisitions and dispositions; pension obligations; cash flow and liquidity; future actions by regulators; and the impact of changes in accounting rules.

Forward-looking statements are subject to inherent risks and uncertainties. Factors that could cause actual results to differ materially from those expressed or implied in our forward-looking statements include:

The factors identified above are not exhaustive. MMC and its subsidiaries operate in a dynamic business environment in which new risks may emerge frequently. Accordingly, MMC cautions readers not to place undue reliance on its forward-looking statements, which speak only as of the dates on which they are made. MMC undertakes no obligation to update or revise any forward-looking statement to reflect events or circumstances arising after the date on which it is made. Further information concerning MMC and its businesses, including information about factors that could materially affect our results of operations and financial condition, is contained in MMC’s filings with the Securities and Exchange Commission, including the “Risk Factors” section of MMC’s most recently filed Annual Report on Form 10-K.

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TABLE OF CONTENTS

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PART I. FINANCIAL INFORMATION

MARSH & McLENNAN COMPANIES, INC.

AND SUBSIDIARIES

CONSOLIDATED STATEMENTS OF INCOME

(Unaudited)

The accompanying notes are an integral part of these consolidated statements.

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MARSH & McLENNAN COMPANIES, INC.

AND SUBSIDIARIES

CONSOLIDATED BALANCE SHEETS

(Unaudited)

The accompanying notes are an integral part of these consolidated statements.

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MARSH & McLENNAN COMPANIES, INC.

AND SUBSIDIARIES

CONSOLIDATED BALANCE SHEETS (Continued)

(Unaudited)

The accompanying notes are an integral part of these consolidated statements.

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MARSH & McLENNAN COMPANIES, INC.

AND SUBSIDIARIES

CONSOLIDATED STATEMENTS OF CASH FLOWS

(Unaudited)

The accompanying notes are an integral part of these consolidated statements.

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MARSH & McLENNANMCLENNAN COMPANIES, INC.

AND SUBSIDIARIES

CONSOLIDATED STATEMENTS OF STOCKHOLDERS’ EQUITY

AND COMPREHENSIVE INCOME

(Unaudited)

The accompanying notes are an integral part of these consolidated statements.

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MARSH & McLENNAN COMPANIES, INC. AND SUBSIDIARIES

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS

(Unaudited)

1.Nature of Operations

(Unaudited)

Marsh & McLennan Companies, Inc. (“MMC”), a global professional services firm, is organized based on the different services that it offers. Under this organizational structure, MMC’s three business segments are: Risk and Insurance Services; Consulting; and Risk Consulting & Technology. As discussed below on August 3, 2010, MMC completed the sale of Kroll to Altegrity, Inc. (“Altegrity”).

The Risk and Insurance Services segment provides risk management and insurance broking, reinsurance broking and insurance program management services for businesses, public entities, insurance companies, associations, professional services organizations, and private clients. MMC conducts business in this segment through Marsh and Guy Carpenter.

In September 2009,the first quarter of 2010, Marsh acquired International Advisory Services,Haake Companies, Inc., one of the largest insurance broking firms in the Midwest and Thomas Rutherfoord, Inc., one of the largest insurance broking firms in the Southeast and mid-Atlantic regions of the U.S. On April 1, 2010, Marsh completed the acquisition of HSBC Insurance Brokers Ltd., an international provider of risk intermediary and risk advisory services. On April 30, 2010, Marsh completed the acquisition of the Bostonian Group Insurance Agency, Inc. and Bostonian Solutions, Inc. (collectively the “Bostonian Group”), one of the largest independent manager of captives and third-partyregional insurance companiesbrokerages in Bermuda. New England.

In April 2009, Guy Carpenter completed the acquisition of John B. Collins Associates, Inc., previously the fifth-largest reinsurance intermediary in the U.S. and seventh-largest in the world. The acquisition of Collins further strengthens Guy Carpenter’s capabilities in medical professional liability, agriculture, Florida property, Program, and regional specialty lines of business. Also, inIn October 2009, Guy Carpenter completed the acquisition of London-based specialty reinsurance broker Rattner Mackenzie Limited from HCC Insurance Holdings, Inc. In September 2009, Marsh acquired International Advisory Services Ltd., the largest independent manager of captives and third-party insurance companies in Bermuda. In December 2009, Marsh acquired the NIA Group, LLC, one of the largest, independent insurance agencies in the Northeast and the 34th largest agency in the U.S.

The Consulting segment provides advice and services to the managements of organizations in the area of human resource consulting, comprising retirement and investments, health and benefits, outsourcing and talent; and strategy and risk management consulting, comprising management, economic and brand consulting. MMC conducts business in this segment through Mercer and Oliver Wyman Group.

The Risk Consulting & Technology segment provides various risk consulting and related risk mitigation services to corporate, government, institutional and individual clients, including consulting services and security services; and technology-enabled services. MMC conducts business in this segment through Kroll. During the second quarter of 2009, Kroll sold Kroll Government Services (“KGS”), which has been classified as a discontinued operation. In the fourth quarter of 2008, the principal operations within the corporate advisory and restructuring business were divested. Additionally, two small residual businesses were exited in the first quarter of 2009. Based on2010, Kroll completed the terms and conditionssale of Kroll Laboratory Specialists (“KLS”). On August 3, 2010, MMC completed the divestitures,sale of Kroll to Altegrity for cash consideration of $1.13 billion. MMC determined it has “continuing involvement”will record the disposal of Kroll in the divested businesses, as that term is used in SEC Staff Accounting Bulletin Topic 5e. Therefore, classificationthird quarter of the corporate advisory2010. The account balances and restructuring businessesactivities of Kroll and KLS were segregated and reported as discontinued operations is not appropriate and their financial results in the currentaccompanying consolidated balance sheets at June 30, 2010 and priorDecember 31, 2009 and the accompanying consolidated statements of income for the three-month and six-month periods areended June 30, 2010 and 2009. The after-tax loss on the disposal of KLS is included in operating income.discontinued operations in 2010.

2.Principles of Consolidation and Other Matters

The consolidated financial statements included herein have been prepared by MMC pursuant to the rules and regulations of the Securities and Exchange Commission. Certain information and footnote disclosures normally included in financial statements prepared in accordance with accounting principles generally accepted in the United States of America, have been omitted pursuant to such rules and regulations for interim filings, although MMC believes that the information and disclosures presented are adequate to make such information and disclosure not misleading. These consolidated financial statements should be read in conjunction with the consolidated financial statements and the notes thereto included in MMC’s Annual Report

on Form 10-K for the year ended December 31, 20082009 (the “2008“2009 10-K”) and the amended financial information filed in MMC’s Current Report on Form 8-K dated August 28, 2009..

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The financial information contained herein reflects all adjustments consisting only of normal recurring adjustments which are, in the opinion of management, necessary for a fair presentation of MMC’s results of operations for the three and nine-monthsix-month periods ended SeptemberJune 30, 20092010 and 2008. Management has evaluated subsequent events through November 5, 2009,2009.

MMC reported a net income tax benefit of $60 million in continuing operations in the datesecond quarter of 2010 on a pretax loss of $89 million, an effective tax rate of 67.4%. The high tax benefit rate primarily reflects the financial statements were issued.

Effective January 1, 2009,combination of the Company adopted retrospectively the new standards issued by the Financial Accounting Standards Board (“FASB”) affecting the calculation of earnings per share, Financial Accounting Standards Codification (“ASC”) Topic No. 260 (“Earnings per Share”) and the presentation of non-controlling interests (previously referred to as minority interests), ASC Topic No. 160 (“Non-controlling Interests”), which are described more fully in Notes 4 and 18tax benefit related to the Consolidated Financial Statements. Also, see Note 5Alaska settlement, determined at U.S. tax rates, with respectother pretax income that is subject to lower average effective tax rates applicable worldwide. Excluding the impact of the Alaska settlement, the effective tax rate for the quarter was 32.3%. The 14.9% effective tax rate for the first six months of 2010 also primarily reflects the benefit associated with the Alaska settlement. Excluding the effect of the settlement, the effective tax rate for the first six months was 29.5%. The increase in effective tax rates compared to 2009, excluding the Alaska settlement, primarily reflects a correctionchange in our Statementsthe worldwide mix of Cash Flows.earnings.

MMC’s 21.9% effective tax rate in the second quarter of 2009 primarily reflects a favorable adjustment from reducing the forecasted, full-year effective tax rate compared with the estimate as of the first quarter. The effective tax rate for the first six months of 2009 was 27.4%.

The caption “Investment income (loss)” in the consolidated statements of income comprises realized and unrealized gains and losses from investments recognized in current earnings. It includes, when applicable, other than temporary declines in the value of available for sale securities and the change in value of MMC’s holdings in certain private equity funds. MMC’s investments may include direct investments in insurance or consulting companies and investments in private equity funds. Equity method gains (losses) of $22$18 million and losses of $19$(33) million are included in this line for the three month periods ended SeptemberJune 30, 2009in 2010 and 2008,2009, respectively. Equity method lossesgains (losses) of $29$17 million and $31$(51) million are included in this line for the ninesix month periods ended SeptemberJune 30, 20092010 and 2008, respectively. During2009.

MMC has an investment in Trident II limited partnership, a private equity investment fund. At June 30, 2010, MMC’s investment in Trident II was approximately $151 million, reflected in the third quarterother assets in consolidated balance sheet. MMC’s maximum exposure to loss is equal to its investment plus any calls on its remaining capital commitment of 2009, MMC recorded an other-than-temporary impairment charge$81 million. Since this fund is closed to new investments, none of $4 million, relatedthe remaining capital commitment is expected to a long-term investment that is carried on the cost basis.be called.

The balance inCompany reports a liability for unrecognized tax benefits resulting from uncertain tax benefits declinedpositions taken or expected to $219 million at the end of the third quarter of 2009 compared with $293 million at the end of 2008. This decline reflects the net impact of expiring statutes of limitations, settlements, and changes in estimates with respect to uncertain tax benefits of prior years, as well as accruals for uncertain tax benefits arising in 2009. The net adjustments with respect to benefits of prior years reduced income tax expense of continuing operationsbe taken in the third quarter of 2009 by $95 million, including the impact of interest and related tax benefits. Of the balance of uncertain tax benefits remaining at the end of the third quarter of 2009, $145 million would reduce the effective tax rate if realized. The liability for interest at the end of the third quarter 2009 was $37 million.return. It is reasonably possible that the total amount of unrecognized tax benefits will decrease between zero and $16approximately $80 million within the next 12twelve months due to settlement of audits and expiration of statutes of limitation. The 27% effective tax rate of the first nine months of 2009 reflects a nondeductible, $315 million non-cash goodwill impairment charge in the second quarter, largely offset by the benefit from reducing unrecognized tax benefits discussed above.

3.Fiduciary Assets and Liabilities

In its capacity as an insurance broker or agent, MMC collects premiums from insureds and, after deducting its commissions, remits the premiums to the respective insurance underwriters. MMC also collects claims or refunds from underwriters on behalf of insureds. Unremitted insurance premiums and claims proceeds are held by MMC in a fiduciary capacity. Risk and Insurance Services revenue includes interest on fiduciary funds of $42$22 million and $114$28 million for the nine-monthsix-month periods ended SeptemberJune 30, 20092010 and 2008,2009, respectively. The Consulting segment recorded fiduciary interest income of $3$2 million and $8 million for each of the comparable periods in 20092010 and 2008, respectively.2009. Since fiduciary assets are not available for corporate use, they are shown in the consolidated balance sheets as an offset to fiduciary liabilities.

Fiduciary assets include approximately $675$371 million and $577 million of fixed income securities classified as available for sale.sale at June 30, 2010 and December 31, 2009, respectively. Unrealized gains or losses from available for sale securities are recorded in other comprehensive income until the securities are disposed of, or mature. Unrealized gains, net of tax, at SeptemberJune 30, 2010 were $8 million and $12 million at June 30, 2010 and December 31, 2009, were $15 million.respectively.

Net uncollected premiums and claims and the related payables amounted to $9.5$10.3 billion at SeptemberJune 30, 20092010 and $8.6$9.9 billion at December 31, 2008.2009. MMC is not a principal to the contracts under which the right to receive premiums or the right to receive reimbursement of insured losses arises. Net uncollected premiums and claims and the related payables are, therefore, not assets and liabilities of MMC and are not included in the accompanying consolidated balance sheets. Mercer had approximately $.4 billion of fiduciary assets at June 30, 2010 and December 31, 2009.

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In certain instances, MMC advances premiums, refunds or claims to insurance underwriters or insureds prior to collection. These advances are made from corporate funds and are reflected in the accompanying consolidated balance sheets as receivables.

4.Per Share Data

Effective January 1, 2009, MMC adopted the guidance in ASC Topic No. 260 – 10 – 45 (“Earnings Per Share”) which applies tofor the calculation of earnings per share (“EPS”) for share-based payment awards with rights to dividends or dividend equivalents. The guidance indicates that unvested share-based payment awards that contain nonforfeitable rights to dividends or dividend equivalents (whether paid or unpaid) are participating securities and should be included in the computation of basic and dilutive EPS using the two-class method. The adoption of this new guidance did not have an impact on the fiscal year 2008 for EPS from continuing operations, discontinued operations and net income because the treasury stock method was more dilutive. The impact of the adoption was a decrease in EPS of $.01, $.07, and $.08 for the fiscal year 2007, for EPS from continuing operations, discontinued operations, and net income, respectively, and a decrease in EPS of $.02, $.01, and $.03 for the fiscal year 2006, for EPS from continuing operations, discontinued operations and net income, respectively.

Basic net income per share attributable to MMC and income from continuing operations per share are calculated by dividing the respective after-tax income attributable to common shares by the weighted average number of outstanding shares of MMC’s common stock.

Diluted net income per share attributable to MMC and income from continuing operations per share are calculated by dividing the respective after-tax income attributable to common shares by the weighted average number of outstanding shares of MMC’s common stock, which have been adjusted for the dilutive effect of potentially issuable common shares (excluding those that are considered participating securities). The diluted earnings per share calculation reflects the more dilutive effect of either (a) the two-class method that assumes that the participating securities have not been exercised or (b) the treasury stock method. Reconciliation of the applicable income components used for diluted earnings per share and basic weighted average common shares outstanding to diluted weighted average common shares outstanding is presented below. Prior period information has been adjusted to conform with the current year presentation in accordance with the retrospective adoption requirements of ASC Topic No. 260 – 10 – 45.