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Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
Originator-Key-Asymmetric:
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 TWSM7vrzLADbmYQaionwg5sDW3P6oaM5D3tdezXMm7z1T+B+twIDAQAB
MIC-Info: RSA-MD5,RSA,
 H4omgLyE3NQuYNXggSdhpSPbLAOjbZnfZlTBbc2AVt1tqlWtv4UUjPG9G6IP9E4s
 u7F0ll1agzSue97U2FVk4Q==

<SEC-DOCUMENT>0000928475-09-000319.txt : 20090612
<SEC-HEADER>0000928475-09-000319.hdr.sgml : 20090612
<ACCEPTANCE-DATETIME>20090612162009
ACCESSION NUMBER:		0000928475-09-000319
CONFORMED SUBMISSION TYPE:	3
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20090610
FILED AS OF DATE:		20090612
DATE AS OF CHANGE:		20090612

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Denner Alexander J
		CENTRAL INDEX KEY:			0001361754

	FILING VALUES:
		FORM TYPE:		3
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-19311
		FILM NUMBER:		09890050

	MAIL ADDRESS:	
		STREET 1:		C/O ICAHN CAPITAL LP
		STREET 2:		767 FIFTH AVENUE, SUITE 4700
		CITY:			NEW YORK
		STATE:			NY
		ZIP:			10153

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			BIOGEN IDEC INC.
		CENTRAL INDEX KEY:			0000875045
		STANDARD INDUSTRIAL CLASSIFICATION:	BIOLOGICAL PRODUCTS (NO DIAGNOSTIC SUBSTANCES) [2836]
		IRS NUMBER:				330112644
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		14 CAMBRIDGE CENTER
		CITY:			CAMBRIDGE
		STATE:			MA
		ZIP:			02142
		BUSINESS PHONE:		6176792000

	MAIL ADDRESS:	
		STREET 1:		14 CAMBRIDGE CENTER
		CITY:			CAMBRIDGE
		STATE:			MA
		ZIP:			02142

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	BIOGEN IDEC INC
		DATE OF NAME CHANGE:	20031112

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	IDEC PHARMACEUTICALS CORP / DE
		DATE OF NAME CHANGE:	19970530
</SEC-HEADER>
<DOCUMENT>
<TYPE>3
<SEQUENCE>1
<FILENAME>form3061209_ex.xml
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0203</schemaVersion>

    <documentType>3</documentType>

    <periodOfReport>2009-06-10</periodOfReport>

    <noSecuritiesOwned>1</noSecuritiesOwned>

    <issuer>
        <issuerCik>0000875045</issuerCik>
        <issuerName>BIOGEN IDEC INC.</issuerName>
        <issuerTradingSymbol>BIIB</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001361754</rptOwnerCik>
            <rptOwnerName>Denner Alexander J</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O ICAHN CAPITAL LP</rptOwnerStreet1>
            <rptOwnerStreet2>767 FIFTH AVENUE, SUITE 4700</rptOwnerStreet2>
            <rptOwnerCity>NEW YORK</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10153</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <ownerSignature>
        <signatureName>ALEXANDER J. DENNER</signatureName>
        <signatureDate>2009-06-12</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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