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Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
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 TWSM7vrzLADbmYQaionwg5sDW3P6oaM5D3tdezXMm7z1T+B+twIDAQAB
MIC-Info: RSA-MD5,RSA,
 I26dNTpst7NehMJxxBjnXnt16skMfglYEs0E9YlR1NjTiFwsmvID7BNZDob9jwN+
 ek3p8fLwmQOxhdEV64Xvaw==

<SEC-DOCUMENT>0001140361-03-002560.txt : 20030723
<SEC-HEADER>0001140361-03-002560.hdr.sgml : 20030723
<ACCEPTANCE-DATETIME>20030723163712
ACCESSION NUMBER:		0001140361-03-002560
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20030721
FILED AS OF DATE:		20030723

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			INSMED INC
		CENTRAL INDEX KEY:			0001104506
		STANDARD INDUSTRIAL CLASSIFICATION:	PHARMACEUTICAL PREPARATIONS [2834]
		IRS NUMBER:				541972729
		STATE OF INCORPORATION:			VA
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		800 E LEIGH ST
		STREET 2:		SUITE 206
		CITY:			RICHMOND
		STATE:			VA
		ZIP:			23219
		BUSINESS PHONE:		8088286893

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			CONDON KENNETH G
		CENTRAL INDEX KEY:			0001218857

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-30739
		FILM NUMBER:		03798683

	BUSINESS ADDRESS:	
		STREET 1:		C/O INSMED INCORPORATED
		STREET 2:		4851 LAKE BROOK DRIVE
		CITY:			GLEN ALLEN
		STATE:			VA
		ZIP:			23060
		BUSINESS PHONE:		804 565 3000

	MAIL ADDRESS:	
		STREET 1:		C/O INSMED INCORP
		STREET 2:		P O BOX 2400
		CITY:			GLEN ALLEN
		STATE:			VA
		ZIP:			23058
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>doc1.xml
<DESCRIPTION>FORM 4
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>
    <schemaVersion>X0101</schemaVersion>

    <documentType>4</documentType>
<periodOfReport>2003-07-21</periodOfReport>
<notSubjectToSection16>0</notSubjectToSection16>
    <issuer>
        <issuerCik>0001104506</issuerCik>
        <issuerName>INSMED INC</issuerName>
        <issuerTradingSymbol>INSM</issuerTradingSymbol>
</issuer>
<reportingOwner>
<reportingOwnerId>
            <rptOwnerCik>0001218857</rptOwnerCik>
            <rptOwnerName>CONDON KENNETH G</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>
<officerTitle></officerTitle>
<otherText></otherText>
</reportingOwnerRelationship>
</reportingOwner>
<nonDerivativeSecurity>
<securityTitle>
<value>Common Stock</value>
</securityTitle>
<transactionDate>
<value>2003-07-21</value>
</transactionDate>
<transactionCoding>
<transactionFormType>4</transactionFormType>
<transactionCode>S</transactionCode>
<equitySwapInvolved>0</equitySwapInvolved>
<footnoteId id="F1"/>
</transactionCoding>
<transactionTimeliness>
<value></value>
</transactionTimeliness>
<transactionAmounts>
<transactionShares>
<value>2500</value>
</transactionShares>
<transactionValue>
<value>.9160</value>
</transactionValue>
<transactionAcquiredDisposedCode>
<value>D</value>
</transactionAcquiredDisposedCode>
</transactionAmounts>
<postTransactionAmounts>
<sharesOwnedFollowingTransaction>
<value>0</value>
<footnoteId id="F2"/>
</sharesOwnedFollowingTransaction>
</postTransactionAmounts>
<ownershipNature>
<directOrIndirectOwnership>
<value>D</value>
</directOrIndirectOwnership>
<natureOfOwnership>
<value></value>
</natureOfOwnership>
</ownershipNature>
</nonDerivativeSecurity>
<footnotes>
<footnote id="F1">Reporting person is selling 2,500 shares at his out of pocket cost to his ex-spouse per a court order.</footnote>
<footnote id="F2">The Reporting Person also has an indirect ownership holding including 532,733 shares owned by Boston University Partnership of which the Reporting Person is a partner except for 15,750 shares which are owned by Trustees of Boston University.  The Reporting Person disclaims beneficial ownership of these securities except to the extent of his proportional interest, and this report shall not be deemed an admission that the Reporting Person is the beneficial owner of the securities for purposes of Section 16 or for any other purpose.</footnote>
</footnotes>
<ownerSignature>
<signatureName>Kevin P. Tully, as Attorney-in-Fact</signatureName>
<signatureDate>2003-07-23</signatureDate>
</ownerSignature>
</ownershipDocument>

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