-----BEGIN PRIVACY-ENHANCED MESSAGE-----
Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
Originator-Key-Asymmetric:
 MFgwCgYEVQgBAQICAf8DSgAwRwJAW2sNKK9AVtBzYZmr6aGjlWyK3XmZv3dTINen
 TWSM7vrzLADbmYQaionwg5sDW3P6oaM5D3tdezXMm7z1T+B+twIDAQAB
MIC-Info: RSA-MD5,RSA,
 OosJ+SJItNtBiXpH8TxCi7IoYppm7Zcy+HDjNvdBh2OjOHyGTP2aevNZ5SLBZyzs
 SLS1A2xf0FKbjr3LpWrS7w==

<SEC-DOCUMENT>0000062709-04-000004.txt : 20040120
<SEC-HEADER>0000062709-04-000004.hdr.sgml : 20040119
<ACCEPTANCE-DATETIME>20040120213559
ACCESSION NUMBER:		0000062709-04-000004
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20040115
FILED AS OF DATE:		20040120

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			COSTER PETER
		CENTRAL INDEX KEY:			0001194445

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-05998
		FILM NUMBER:		04533756

	BUSINESS ADDRESS:	
		STREET 1:		MERCER CONSULTING GROUP INC
		STREET 2:		1166 AVE OF THE AMERICAS
		CITY:			NEW YORK
		STATE:			NY
		ZIP:			10036

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			MARSH & MCLENNAN COMPANIES INC
		CENTRAL INDEX KEY:			0000062709
		STANDARD INDUSTRIAL CLASSIFICATION:	INSURANCE AGENTS BROKERS & SERVICES [6411]
		IRS NUMBER:				362668272
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		1166 AVENUE OF THE AMERICAS
		CITY:			NEW YORK
		STATE:			NY
		ZIP:			10036
		BUSINESS PHONE:		2123455000

	MAIL ADDRESS:	
		STREET 1:		1166 AVENUE OF THE AMERICAS
		CITY:			NEW YORK
		STATE:			NY
		ZIP:			10036

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	MARLENNAN CORP
		DATE OF NAME CHANGE:	19760505
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>edgar.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>
    <schemaVersion>X0201</schemaVersion>

    <documentType>4</documentType><periodOfReport>2004-01-15</periodOfReport>
    <issuer>
        <issuerCik>0000062709</issuerCik>
        <issuerName>MARSH &amp; MCLENNAN COMPANIES INC</issuerName>
        <issuerTradingSymbol>MMC</issuerTradingSymbol></issuer><reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001194445</rptOwnerCik>
            <rptOwnerName>COSTER PETER</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>1166 AVENUE OF THE AMERICAS</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>NEW YORK</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10036-2774</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
            <reportingOwnerRelationship>
<isDirector>1</isDirector><isOfficer>1</isOfficer><isTenPercentOwner>0</isTenPercentOwner><isOther>0</isOther><officerTitle>PRESIDENT,  MERCER INC.</officerTitle></reportingOwnerRelationship></reportingOwner><nonDerivativeTable><nonDerivativeTransaction><securityTitle><value>COMMON</value></securityTitle><transactionDate><value>2004-01-18</value></transactionDate><transactionCoding><transactionFormType>4</transactionFormType><transactionCode>M</transactionCode><equitySwapInvolved>0</equitySwapInvolved></transactionCoding><transactionAmounts><transactionShares><value>19484</value><footnoteId id="F1"/></transactionShares><transactionPricePerShare><footnoteId id="F6"/></transactionPricePerShare><transactionAcquiredDisposedCode><value>A</value></transactionAcquiredDisposedCode></transactionAmounts><postTransactionAmounts><sharesOwnedFollowingTransaction><value>231712</value></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwn
ership><natureOfOwnership><value/></natureOfOwnership></ownershipNature></nonDerivativeTransaction><nonDerivativeTransaction><securityTitle><value>COMMON</value></securityTitle><transactionDate><value>2004-01-18</value></transactionDate><transactionCoding><transactionFormType>4</transactionFormType><transactionCode>F</transactionCode><equitySwapInvolved>0</equitySwapInvolved></transactionCoding><transactionAmounts><transactionShares><value>6752</value><footnoteId id="F1"/></transactionShares><transactionPricePerShare><value>47.915</value></transactionPricePerShare><transactionAcquiredDisposedCode><value>D</value></transactionAcquiredDisposedCode></transactionAmounts><postTransactionAmounts><sharesOwnedFollowingTransaction><value>224960</value><footnoteId id="F2"/></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value/></natureOfOwnership></ownershipNature></nonDerivativeTransaction><nonDeriva
tiveTransaction><securityTitle><value>COMMON</value></securityTitle><transactionDate><value>2003-09-30</value></transactionDate><transactionCoding><transactionFormType>4</transactionFormType><transactionCode>J</transactionCode><equitySwapInvolved>0</equitySwapInvolved></transactionCoding><transactionAmounts><transactionShares><value>74.3371</value><footnoteId id="F3"/></transactionShares><transactionPricePerShare><footnoteId id="F6"/></transactionPricePerShare><transactionAcquiredDisposedCode><value>A</value></transactionAcquiredDisposedCode></transactionAmounts><postTransactionAmounts><sharesOwnedFollowingTransaction><value>432.9523</value></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>I</value></directOrIndirectOwnership><natureOfOwnership><value>STOCK INVESTMENT PLAN (401K)</value></natureOfOwnership></ownershipNature></nonDerivativeTransaction></nonDerivativeTable><derivativeTable><derivativeTransaction><securityTitle><value>RESTRICTED STOCK 
UNITS</value></securityTitle><conversionOrExercisePrice><footnoteId id="F5"/></conversionOrExercisePrice><transactionDate><value>2004-01-15</value></transactionDate><transactionCoding><transactionFormType>4</transactionFormType><transactionCode>A</transactionCode><equitySwapInvolved>0</equitySwapInvolved></transactionCoding><transactionAmounts><transactionShares><value>16971</value></transactionShares><transactionPricePerShare><footnoteId id="F6"/></transactionPricePerShare><transactionAcquiredDisposedCode><value>A</value></transactionAcquiredDisposedCode></transactionAmounts><exerciseDate><footnoteId id="F6"/></exerciseDate><expirationDate><footnoteId id="F6"/></expirationDate><underlyingSecurity><underlyingSecurityTitle><value>COMMON</value></underlyingSecurityTitle><underlyingSecurityShares><value>16971</value></underlyingSecurityShares></underlyingSecurity><postTransactionAmounts><sharesOwnedFollowingTransaction><value>136172</value></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNat
ure><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value/></natureOfOwnership></ownershipNature></derivativeTransaction><derivativeTransaction><securityTitle><value>RESTRICTED STOCK UNITS</value></securityTitle><conversionOrExercisePrice><footnoteId id="F5"/></conversionOrExercisePrice><transactionDate><value>2004-01-18</value></transactionDate><transactionCoding><transactionFormType>4</transactionFormType><transactionCode>M</transactionCode><equitySwapInvolved>0</equitySwapInvolved></transactionCoding><transactionAmounts><transactionShares><value>19484</value><footnoteId id="F1"/></transactionShares><transactionPricePerShare><footnoteId id="F6"/></transactionPricePerShare><transactionAcquiredDisposedCode><value>D</value></transactionAcquiredDisposedCode></transactionAmounts><exerciseDate><footnoteId id="F6"/></exerciseDate><expirationDate><footnoteId id="F6"/></expirationDate><underlyingSecurity><underlyingSecurityTitle><value>COMMON</value></underlyingSecurityTit
le><underlyingSecurityShares><value>19484</value></underlyingSecurityShares></underlyingSecurity><postTransactionAmounts><sharesOwnedFollowingTransaction><value>116688</value></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value/></natureOfOwnership></ownershipNature></derivativeTransaction><derivativeTransaction><securityTitle><value>SISP RS UNITS</value></securityTitle><conversionOrExercisePrice><footnoteId id="F5"/></conversionOrExercisePrice><transactionDate><value>2003-09-30</value></transactionDate><transactionCoding><transactionFormType>4</transactionFormType><transactionCode>J</transactionCode><equitySwapInvolved>0</equitySwapInvolved></transactionCoding><transactionAmounts><transactionShares><value>1894.0905</value><footnoteId id="F4"/></transactionShares><transactionPricePerShare><footnoteId id="F6"/></transactionPricePerShare><transactionAcquiredDisposedCode><value>A</value></tran
sactionAcquiredDisposedCode></transactionAmounts><exerciseDate><footnoteId id="F6"/></exerciseDate><expirationDate><footnoteId id="F6"/></expirationDate><underlyingSecurity><underlyingSecurityTitle><value>COMMON</value></underlyingSecurityTitle><underlyingSecurityShares><value>1894.0905</value></underlyingSecurityShares></underlyingSecurity><postTransactionAmounts><sharesOwnedFollowingTransaction><value>30185.1596</value></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value/></natureOfOwnership></ownershipNature></derivativeTransaction></derivativeTable><footnotes><footnote id="F1">Vesting and distribution to reporting person of 19,484 shares of Restricted Stock Units of which 6,752 shares were withheld to cover applicable taxes.</footnote><footnote id="F2">Includes 154,900 shares of restricted stock.</footnote><footnote id="F3">Reflects additional shares acquired by the Stock Investment Pla
n (SIP) Custodian at prevailing market prices.  Information reported herein is based on reporting person's Plan Statement as of September 30, 2003.</footnote><footnote id="F4">Reflects additional shares acquired by the Stock Investment Supplemental Plan (SISP) Custodian at prevailing market prices.  Information reported herein is based on reporting person's Plan Statement as of September 30, 2003.</footnote><footnote id="F5">The security converts to common stock on a one-for-one basis.</footnote><footnote id="F6">Not Applicable.</footnote></footnotes><remarks/><ownerSignature><signatureName>WILLIAM J. WHITE,  Attorney-in-fact</signatureName><signatureDate>2004-01-20</signatureDate></ownerSignature></ownershipDocument>

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</SEC-DOCUMENT>
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