-----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,
 SnvJ2p6xzEh4Nuf+Sfs0lLo0sib8qd9CpBYQiie8eoaptiM3EJv0ZNUbSidJCy8n
 nCt0PM5254AyXgU/NTGb2Q==

<SEC-DOCUMENT>0001209191-03-013213.txt : 20030724
<SEC-HEADER>0001209191-03-013213.hdr.sgml : 20030724
<ACCEPTANCE-DATETIME>20030724141008
ACCESSION NUMBER:		0001209191-03-013213
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20030722
FILED AS OF DATE:		20030724

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			DALEY WILLIAM M
		CENTRAL INDEX KEY:			0001183865

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-03305
		FILM NUMBER:		03800636

	MAIL ADDRESS:	
		STREET 1:		175 E HOUSTON STREET
		STREET 2:		ROOM 216
		CITY:			SAN ANTONIO
		STATE:			TX
		ZIP:			78205

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			MERCK & CO INC
		CENTRAL INDEX KEY:			0000064978
		STANDARD INDUSTRIAL CLASSIFICATION:	PHARMACEUTICAL PREPARATIONS [2834]
		IRS NUMBER:				221109110
		STATE OF INCORPORATION:			NJ
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		ONE MERCK DR
		STREET 2:		P O BOX 100
		CITY:			WHITEHOUSE STATION
		STATE:			NJ
		ZIP:			08889-0100
		BUSINESS PHONE:		9084234044

	MAIL ADDRESS:	
		STREET 1:		ONE MERCK DR
		STREET 2:		PO BOX 100 WS3AB-05
		CITY:			WHITEHOUSE STATION
		STATE:			NJ
		ZIP:			08889-0100
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>doc4.xml
<DESCRIPTION>FORM 4 SUBMISSION
<TEXT>
<XML>
<?xml version="1.0"?><ownershipDocument>
    <schemaVersion>X0101</schemaVersion>

    <documentType>4</documentType><periodOfReport>2003-07-22</periodOfReport><notSubjectToSection16>0</notSubjectToSection16>
    <issuer>
        <issuerCik>0000064978</issuerCik>
        <issuerName>MERCK &amp; CO INC</issuerName>
        <issuerTradingSymbol>(MRK)</issuerTradingSymbol></issuer><reportingOwner><reportingOwnerId>
            <rptOwnerCik>0001183865</rptOwnerCik>
            <rptOwnerName>DALEY WILLIAM M</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>  </rptOwnerStreet1>
            <rptOwnerStreet2>  </rptOwnerStreet2>
            <rptOwnerCity>  </rptOwnerCity>
            <rptOwnerState>  </rptOwnerState>
            <rptOwnerZipCode>  </rptOwnerZipCode>
        </reportingOwnerAddress>
            <reportingOwnerRelationship>
<isDirector>1</isDirector><isOfficer>0</isOfficer><isTenPercentOwner>0</isTenPercentOwner><isOther>0</isOther></reportingOwnerRelationship></reportingOwner><derivativeSecurity><securityTitle><value>Phantom Stock</value></securityTitle><conversionOrExercisePrice><value>0</value><footnoteId id="F1" /></conversionOrExercisePrice><transactionDate><value>2003-07-22</value></transactionDate><transactionCoding><transactionFormType>4</transactionFormType><transactionCode>A</transactionCode><equitySwapInvolved>0</equitySwapInvolved></transactionCoding><transactionTimeliness><value></value></transactionTimeliness><transactionAmounts><transactionShares><value>20.7577</value></transactionShares><transactionValue><value>57.81</value></transactionValue><transactionAcquiredDisposedCode><value>A</value></transactionAcquiredDisposedCode></transactionAmounts><exerciseDate><value>1988-08-08</value><footnoteId id="F2" /></exerciseDate><expirationDate><value>1988-08-08</value><footnoteId id="F2" /></expirationDate><underlyingSec
urity><underlyingSecurityTitle><value>Common Stock</value></underlyingSecurityTitle><underlyingSecurityShares><value>20.7577</value></underlyingSecurityShares></underlyingSecurity><postTransactionAmounts><sharesOwnedFollowingTransaction><value>1886.5807</value><footnoteId id="F3" /></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership></ownershipNature></derivativeSecurity><footnotes><footnote id="F1">1-for-1</footnote><footnote id="F2">[This date entry is made pursuant to SEC EDGAR guidelines in effect until system modifications are implemented.]  Phantom stock units are to be settled 100% in cash upon reporting person's termination of service in accordance with a distribution schedule elected pursuant to the terms of the Plan for Deferred Payment of Director's Compensation.</footnote><footnote id="F3">Holdings include shares acquired in dividend reinvestment transactions.</footnote></footnotes><ownerSignature><sign
atureName>Nancy V. Van Allen as Attorney-in-Fact for
William M. Daley</signatureName><signatureDate>2003-07-24</signatureDate></ownerSignature></ownershipDocument>

</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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