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Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
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<SEC-DOCUMENT>0001123292-09-000113.txt : 20090205
<SEC-HEADER>0001123292-09-000113.hdr.sgml : 20090205
<ACCEPTANCE-DATETIME>20090205152815
ACCESSION NUMBER:		0001123292-09-000113
CONFORMED SUBMISSION TYPE:	3
PUBLIC DOCUMENT COUNT:		2
CONFORMED PERIOD OF REPORT:	20090127
FILED AS OF DATE:		20090205
DATE AS OF CHANGE:		20090205

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			BREWER RICHARD B
		CENTRAL INDEX KEY:			0001189164

	FILING VALUES:
		FORM TYPE:		3
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-22873
		FILM NUMBER:		09572893

	BUSINESS ADDRESS:	
		BUSINESS PHONE:		2068291643

	MAIL ADDRESS:	
		STREET 1:		C/O DENDREON CORP
		STREET 2:		3005 1ST AVE
		CITY:			SEATTLE
		STATE:			WA
		ZIP:			98121

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			ARCA biopharma, Inc.
		CENTRAL INDEX KEY:			0000907654
		STANDARD INDUSTRIAL CLASSIFICATION:	IN VITRO & IN VIVO DIAGNOSTIC SUBSTANCES [2835]
		IRS NUMBER:				363855489
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		8001 ARISTA PLACE
		STREET 2:		SUITE 200
		CITY:			BROOMFIELD
		STATE:			CO
		ZIP:			80021
		BUSINESS PHONE:		720-940-2200

	MAIL ADDRESS:	
		STREET 1:		8001 ARISTA PLACE
		STREET 2:		SUITE 200
		CITY:			BROOMFIELD
		STATE:			CO
		ZIP:			80021

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	NUVELO INC
		DATE OF NAME CHANGE:	20030203

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	HYSEQ INC
		DATE OF NAME CHANGE:	19970610
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<SEQUENCE>1
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<ownershipDocument>

    <schemaVersion>X0203</schemaVersion>

    <documentType>3</documentType>

    <periodOfReport>2009-01-27</periodOfReport>

    <noSecuritiesOwned>0</noSecuritiesOwned>

    <issuer>
        <issuerCik>0000907654</issuerCik>
        <issuerName>ARCA biopharma, Inc.</issuerName>
        <issuerTradingSymbol>ABIO</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001189164</rptOwnerCik>
            <rptOwnerName>BREWER RICHARD B</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O ARCA BIOPHARMA, INC.</rptOwnerStreet1>
            <rptOwnerStreet2>8001 ARISTA PLACE, SUITE 200</rptOwnerStreet2>
            <rptOwnerCity>BROOMFIELD</rptOwnerCity>
            <rptOwnerState>CO</rptOwnerState>
            <rptOwnerZipCode>80021</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>President and CEO</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>83490</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeHolding>
            <securityTitle>
                <value>Option to Purchase Common Stock</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>.90</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <footnoteId id="F1"/>
            </exerciseDate>
            <expirationDate>
                <value>2016-11-02</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>165644</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Option to Purchase Common Stock</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>5.57</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <footnoteId id="F2"/>
            </exerciseDate>
            <expirationDate>
                <value>2019-01-22</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>25047</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeHolding>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">The options are exercisable immediately and if exercised are subject to ARCA's right of repurchase, which lapses at the rate of 25%  upon grant and 6.25% at the end of each three-month period following the first anniversary of the November 2, 2006 grant date. Of these options, as of January 27, 2009, 82,822 were subject to a right of repurchase in favor of ARCA.</footnote>
        <footnote id="F2">The options vest in equal monthly installments over a four year period from the date of grant</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>Patrick Wheeler, attorney in fact</signatureName>
        <signatureDate>2009-02-05</signatureDate>
    </ownerSignature>
</ownershipDocument>
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<p style=' margin-bottom:0pt; margin-top:0pt;text-align:center;'><b><small>ARCA</small> <small>BIOPHARMA,</small> <small>INC.</small></b></p>

<p style=' margin-bottom:0pt; margin-top:0pt;text-align:center;'><font size=2>&nbsp;</font></p>

<p style=' margin-bottom:12pt; margin-top:0pt;text-align:center;'><B><font SIZE=2>POWER OF ATTORNEY</font></B></p>

<p style=' margin-bottom:12pt; margin-top:0pt; text-indent:0.5in;text-align:left;'><font size=2>Know all by these presents, that the undersigned hereby constitutes and appoints each of Christopher Ozeroff, Patrick Wheeler, Brian Selby and Paula Evans, signing singly, and with full power of substitution, the undersigned&#146;s true and lawful attorney-in-fact to:</font></p>

<p style=' margin-bottom:12pt; margin-top:0pt; text-indent:0.54in;text-align:left;'><font size=2> (1)&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;execute and file for and on behalf of the undersigned, in the undersigned&#146;s name, place and stead, in any and all capacities, all Forms 3, 4 and 5 (including any amendments thereto) that the undersigned may be required to file with the United States Securities and Exchange Commission as a result of the undersigned&#146;s ownership of or transactions in securities of ARCA biopharma, Inc. (the &#147;</font><u><font size=2>Company</font></u><font size=2>&#148;);</font></p>

<p style=' margin-bottom:12pt; margin-top:0pt; text-indent:0.54in;text-align:left;'><font size=2> (2)&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;do and perform any and all acts for and on behalf of the undersigned which may be necessary or desirable to complete and execute any such Form 3, 4 or 5 and timely file any such form with the United States Securities and Exchange Commission and any stock exchange or similar authority; and</font></p>

<p style=' margin-bottom:12pt; margin-top:0pt; text-indent:0.54in;text-align:left;'><font size=2> (3)&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;take any other action of any type whatsoever in connection with the foregoing which, in the opinion of such attorney-in-fact, may be of benefit to, and in the best interest of, or legally required by, the undersigned.</font></p>

<p style=' margin-bottom:12pt; margin-top:0pt; text-indent:0.5in;text-align:left;'><font size=2>The undersigned hereby grants to each such attorney-in-fact full power and authority to do and perform any and every act and thing whatsoever requisite, necessary, or proper to be done in the exercise of any of the rights and powers herein granted, as fully to all intents and purposes as the undersigned might or could do if personally present, with full power of substitution or revocation, hereby ratifying and confirming all that such attorney-in-fact, or such attorney-in-fact&#146;s substitute or substitutes, shall lawfully do or cause to be done by virtue of this power of attorney and the rights and powers herein granted.  The undersigned acknowledges that the foregoing attorneys-in-fact, in serving in such capacity at the request of the undersigned, are not assuming, nor is the Company assuming, any of the undersigned&#146;s responsibilities to comply with Section 16 of the Securities
Exchange Act of 1934.</font></p>

<p style=' margin-bottom:12pt; margin-top:0pt; text-indent:0.5in;text-align:left;'><font size=2>This Power of Attorney shall remain in full force and effect until the undersigned is no longer required to file Forms 3, 4 and 5 with respect to the undersigned&#146;s holdings of and transactions in securities issued by the Company, unless earlier revoked by the undersigned in a signed writing delivered to the foregoing attorneys-in-fact.</font></p>

<p style=' margin-bottom:0pt; margin-top:0pt;text-align:left;'><font size=2>&nbsp;</font></p>

<p style=' margin-bottom:0pt; margin-top:0pt;text-align:left;'>&nbsp;</p>


<p style=' margin-bottom:0pt; margin-top:0pt;text-align:left;'>
<font size=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;IN WITNESS WHEREOF, the undersigned has caused this Power of Attorney to be executed as of January 27, 2009.</font></p>

<p style=' margin-bottom:0pt; margin-top:0pt;text-align:left;'><font size=2>&nbsp;</font></p>

<p style=' margin-bottom:0pt; margin-top:0pt; margin-left:3.5in;text-align:left;'><u><font size=2>/s/ Richard B. Brewer</font></u></p>

<p style=' margin-bottom:0pt; margin-top:0pt; margin-left:3.5in;text-align:left;'><font size=2>Signature</font></p>

<p style=' margin-bottom:0pt; margin-top:0pt; margin-left:3.5in;text-align:left;'><font size=2>&nbsp;</font></p>

<p style=' margin-bottom:0pt; margin-top:0pt; margin-left:3.5in;text-align:left;'><u><font size=2>Richard B. Brewer</font></u></p>


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<p style=' margin-bottom:0pt; margin-top:0pt;text-align:left;'>&nbsp;</p>

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<p style=' margin-bottom:0pt; margin-top:0pt;text-align:left;'><font size=2>&nbsp;</font></p>



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