-----BEGIN PRIVACY-ENHANCED MESSAGE-----
Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
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 TWSM7vrzLADbmYQaionwg5sDW3P6oaM5D3tdezXMm7z1T+B+twIDAQAB
MIC-Info: RSA-MD5,RSA,
 GLDYdtuHi+G9uPKavelDLnIhQKV7Kem8Lm+xkzqPuSRKBrCkywpZyEJV6sXh9ptj
 c8c637kwObpUbDEVafsgPg==

<SEC-DOCUMENT>0001179110-06-002340.txt : 20060130
<SEC-HEADER>0001179110-06-002340.hdr.sgml : 20060130
<ACCEPTANCE-DATETIME>20060130182606
ACCESSION NUMBER:		0001179110-06-002340
CONFORMED SUBMISSION TYPE:	3
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20060124
FILED AS OF DATE:		20060130
DATE AS OF CHANGE:		20060130

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			KNOTT DAVID M
		CENTRAL INDEX KEY:			0000808722

	FILING VALUES:
		FORM TYPE:		3
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-21898
		FILM NUMBER:		06563470

	MAIL ADDRESS:	
		STREET 1:		485 UNDERHILL BLVD
		STREET 2:		STE 205
		CITY:			SYOSSET
		STATE:			NY
		ZIP:			11791-3419

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			ARROWHEAD RESEARCH CORP
		CENTRAL INDEX KEY:			0000879407
		STANDARD INDUSTRIAL CLASSIFICATION:	SERVICES-COMMERCIAL PHYSICAL & BIOLOGICAL RESEARCH [8731]
		IRS NUMBER:				460408024
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			0930

	BUSINESS ADDRESS:	
		STREET 1:		1118 EAST GREEN STREET
		CITY:			PASADENA
		STATE:			CA
		ZIP:			91106
		BUSINESS PHONE:		626-792-5549

	MAIL ADDRESS:	
		STREET 1:		1118 EAST GREEN STREET
		CITY:			PASADENA
		STATE:			CA
		ZIP:			91106

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	INTERACTIVE GROUP INC
		DATE OF NAME CHANGE:	20020509

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	INTERACTIVE INC
		DATE OF NAME CHANGE:	19940224
</SEC-HEADER>
<DOCUMENT>
<TYPE>3
<SEQUENCE>1
<FILENAME>edgar.xml
<DESCRIPTION>FORM 3 -
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0202</schemaVersion>

    <documentType>3</documentType>

    <periodOfReport>2006-01-24</periodOfReport>

    <noSecuritiesOwned>0</noSecuritiesOwned>

    <issuer>
        <issuerCik>0000879407</issuerCik>
        <issuerName>ARROWHEAD RESEARCH CORP</issuerName>
        <issuerTradingSymbol>ARWR</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0000808722</rptOwnerCik>
            <rptOwnerName>KNOTT DAVID M</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>485 UNDERHILL BLVD</rptOwnerStreet1>
            <rptOwnerStreet2>SUITE 205</rptOwnerStreet2>
            <rptOwnerCity>SYOSSET</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>11791</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle></officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common stock, $0.001 par value per share</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>40300</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Anno, L.P.</value>
                    <footnoteId id="F1"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common stock, $0.001 par value per share</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>160200</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Commonfund Hedged Equity Company</value>
                    <footnoteId id="F1"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common stock, $0.001 par value per share</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>45600</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Good Steward Trading Company SPC</value>
                    <footnoteId id="F1"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common stock, $0.001 par value per share</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>1330500</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Knott Partners, L.P.</value>
                    <footnoteId id="F1"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common stock, $0.001 par value per share</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>1739181</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Matterhorn Offshore Fund Limited</value>
                    <footnoteId id="F1"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common stock, $0.001 par value per share</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>733800</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Shoshone Partners, LP</value>
                    <footnoteId id="F1"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeHolding>
            <securityTitle>
                <value>Warrant to purchase Common Stock, $0.001 par value per share</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>4.50</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2006-07-25</value>
            </exerciseDate>
            <expirationDate>
                <value>2011-01-24</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock, $0.001 par value per share</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>3075</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Anno, L.P.</value>
                    <footnoteId id="F1"/>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Warrant to purchase Common Stock, $0.001 par value per share</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>4.50</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2006-07-25</value>
            </exerciseDate>
            <expirationDate>
                <value>2011-01-24</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock, $0.001 par value per share</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>12075</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Commonfund Hedged Equity Company</value>
                    <footnoteId id="F1"/>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Warrant to purchase Common Stock, $0.001 par value per share</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>4.50</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2006-07-25</value>
            </exerciseDate>
            <expirationDate>
                <value>2011-01-24</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock, $0.001 par value per share</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>3450</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Good Steward Trading Company SPC</value>
                    <footnoteId id="F1"/>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Warrant to purchase Common Stock, $0.001 par value per share</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>4.50</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2006-07-25</value>
            </exerciseDate>
            <expirationDate>
                <value>2011-01-24</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock, $0.001 par value per share</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>108475</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Knott Partners, L.P.</value>
                    <footnoteId id="F1"/>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Warrant to purchase Common Stock, $0.001 par value per share</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>4.50</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2006-07-25</value>
            </exerciseDate>
            <expirationDate>
                <value>2011-01-24</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock, $0.001 par value per share</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>161688</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Matterhorn Offshore Fund Limited</value>
                    <footnoteId id="F1"/>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Warrant to purchase Common Stock, $0.001 par value per share</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>4.50</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2006-07-25</value>
            </exerciseDate>
            <expirationDate>
                <value>2011-01-24</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock, $0.001 par value per share</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>68400</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Shoshone Partners, LP</value>
                    <footnoteId id="F1"/>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeHolding>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">The Reporting Person is the managing member of Knott Partners Management, LLC, which is the sole General Partner of Shoshone Partners, L.P. and managing general partner of Knott Partners, L.P.  In addition, the Reporting Person is the sole shareholder, director and president of Dorset Management Corporation, which provides investment management services to those entities listed in Table I(3).  As a result of the Reporting Person's interests in Knott Partners Management, LLC and Dorset Management Corporation, the Reporting Person has investment discretion and control in the securities in Table I(2).  The Reporting Person may be deemed to beneficially own indirect pecuniary interest in securities in Table I(2) as a result of a performance related fee. The Reporting Person disclaims beneficial ownership therein except to the extent ultimately realized.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>David M. Knott</signatureName>
        <signatureDate>2006-01-30</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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