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Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
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MIC-Info: RSA-MD5,RSA,
 BhRLU9P3E2HaQbnhdWJtvVNHo6dGxsNHyP5WjJa/+wci573DzpLUxKex4geeNukX
 cXrAqUXVMt/1d0A1DgSy4A==

<SEC-DOCUMENT>0001209191-03-014545.txt : 20030731
<SEC-HEADER>0001209191-03-014545.hdr.sgml : 20030731
<ACCEPTANCE-DATETIME>20030731120555
ACCESSION NUMBER:		0001209191-03-014545
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20030730
FILED AS OF DATE:		20030731

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

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			WOLD OLSEN PER
		CENTRAL INDEX KEY:			0001181185

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-03305
		FILM NUMBER:		03813696

	BUSINESS ADDRESS:	
		STREET 1:		MERCK & CO INC
		STREET 2:		ONE MERCK DR PO BOX 100
		CITY:			WHITEHOUSE STATION
		STATE:			NJ
		ZIP:			08889
		BUSINESS PHONE:		9084231000
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>doc4.xml
<DESCRIPTION>FORM 4 SUBMISSION
<TEXT>
<XML>
<?xml version="1.0"?><ownershipDocument>
    <schemaVersion>X0201</schemaVersion>

    <documentType>4</documentType><periodOfReport>2003-07-30</periodOfReport><notSubjectToSection16>0</notSubjectToSection16>
    <issuer>
        <issuerCik>0000064978</issuerCik>
        <issuerName>MERCK &amp; CO INC</issuerName>
        <issuerTradingSymbol>(MRK)</issuerTradingSymbol></issuer><reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001181185</rptOwnerCik>
            <rptOwnerName>WOLD OLSEN PER</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>ONE MERCK DRIVE</rptOwnerStreet1>
            <rptOwnerStreet2>P. O. BOX 100</rptOwnerStreet2>
            <rptOwnerCity>WHITEHOUSE STATION</rptOwnerCity>
            <rptOwnerState>NJ</rptOwnerState>
            <rptOwnerZipCode>0889-0100</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
            <reportingOwnerRelationship>
<isDirector>0</isDirector><isOfficer>1</isOfficer><isTenPercentOwner>0</isTenPercentOwner><isOther>0</isOther><officerTitle>Pres.,HH,Euro./Mid.East/Africa</officerTitle></reportingOwnerRelationship></reportingOwner><nonDerivativeTable><nonDerivativeTransaction><securityTitle><value>Common Stock</value></securityTitle><transactionDate><value>2003-07-30</value></transactionDate><transactionCoding><transactionFormType>4</transactionFormType><transactionCode>M</transactionCode><equitySwapInvolved>0</equitySwapInvolved></transactionCoding><transactionTimeliness><value></value></transactionTimeliness><transactionAmounts><transactionShares><value>600</value></transactionShares><transactionPricePerShare><value>16.25</value></transactionPricePerShare><transactionAcquiredDisposedCode><value>A</value></transactionAcquiredDisposedCode></transactionAmounts><postTransactionAmounts><sharesOwnedFollowingTransaction><value>121996</value></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndi
rectOwnership><value>D</value></directOrIndirectOwnership></ownershipNature></nonDerivativeTransaction><nonDerivativeHolding><securityTitle><value>Common Stock - 401(k) Plan</value></securityTitle><postTransactionAmounts><sharesOwnedFollowingTransaction><value>6345.4527</value><footnoteId id="F1" /></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>I</value></directOrIndirectOwnership><natureOfOwnership><value>By 401(k)</value></natureOfOwnership></ownershipNature></nonDerivativeHolding></nonDerivativeTable><derivativeTable><derivativeTransaction><securityTitle><value>Employee Stock Option - 1993/10/20 (right to buy)</value></securityTitle><conversionOrExercisePrice><value>16.25</value></conversionOrExercisePrice><transactionDate><value>2003-07-30</value></transactionDate><transactionCoding><transactionFormType>4</transactionFormType><transactionCode>M</transactionCode><equitySwapInvolved>0</equitySwapInvolved></transactionCoding><transactionAmounts>
<transactionShares><value>600</value></transactionShares><transactionPricePerShare><value>0</value></transactionPricePerShare><transactionAcquiredDisposedCode><value>D</value></transactionAcquiredDisposedCode></transactionAmounts><exerciseDate><value>1998-10-20</value></exerciseDate><expirationDate><value>2003-10-19</value></expirationDate><underlyingSecurity><underlyingSecurityTitle><value>Common Stock</value></underlyingSecurityTitle><underlyingSecurityShares><value>600</value></underlyingSecurityShares></underlyingSecurity><postTransactionAmounts><sharesOwnedFollowingTransaction><value>0</value></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership></ownershipNature></derivativeTransaction></derivativeTable><footnotes><footnote id="F1">Includes shares acquired and dividends earned through July 1, 2003 in the Merck &amp; Co., Inc. Employee Savings and Security Plan, a 401(k) plan.</footnote></footnotes><remarks></re
marks><ownerSignature><signatureName>Nancy V. Van Allen as Attorney-in-Fact for
Per Wold-Olsen</signatureName><signatureDate>2003-07-31</signatureDate></ownerSignature></ownershipDocument>

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