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Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
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MIC-Info: RSA-MD5,RSA,
 NjiMYYPc2KeQNBKk9LuraE8rZTqmjcndzmoz2vQL6GqszxesUpbia7smrky04EJ3
 G9rcRDvqKVYFD99/RAXXUQ==

<SEC-DOCUMENT>0001179110-07-017599.txt : 20070830
<SEC-HEADER>0001179110-07-017599.hdr.sgml : 20070830
<ACCEPTANCE-DATETIME>20070830111349
ACCESSION NUMBER:		0001179110-07-017599
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20070829
FILED AS OF DATE:		20070830
DATE AS OF CHANGE:		20070830

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			MATHSTAR INC
		CENTRAL INDEX KEY:			0001118037
		STANDARD INDUSTRIAL CLASSIFICATION:	SEMICONDUCTORS & RELATED DEVICES [3674]
		IRS NUMBER:				000000000
		STATE OF INCORPORATION:			MN
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		19075 NORTHWEST TANASBOURNE DRIVE
		STREET 2:		SUITE 200
		CITY:			HILLSBORO
		STATE:			OR
		ZIP:			97124
		BUSINESS PHONE:		503-726-5500

	MAIL ADDRESS:	
		STREET 1:		19075 NORTHWEST TANASBOURNE DRIVE
		STREET 2:		SUITE 200
		CITY:			HILLSBORO
		STATE:			OR
		ZIP:			97124

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			CRUCKSHANK JAMES W
		CENTRAL INDEX KEY:			0001274643

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-51560
		FILM NUMBER:		071089896

	MAIL ADDRESS:	
		STREET 1:		5920 FRIARS ROAD
		STREET 2:		SUITE 104
		CITY:			SAN DIEGO
		STATE:			CA
		ZIP:			92108
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>edgar.xml
<DESCRIPTION>FORM 4 -
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2007-08-29</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001118037</issuerCik>
        <issuerName>MATHSTAR INC</issuerName>
        <issuerTradingSymbol>MATH</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001274643</rptOwnerCik>
            <rptOwnerName>CRUCKSHANK JAMES W</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>19075 NW TANASBOURNE DRIVE #200</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>HILLSBORO</rptOwnerCity>
            <rptOwnerState>OR</rptOwnerState>
            <rptOwnerZipCode>97124</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>CFO and VP of Administration</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2007-08-29</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>10000</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>1.11</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>83750</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2007-08-29</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>10000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>1.10</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>93750</value>
                    <footnoteId id="F3"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>See Footnote</value>
                    <footnoteId id="F2"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">Shares purchased by Mr. Cruckshank to be held in his Individual Retirement Account</footnote>
        <footnote id="F2">Shares purchased by Mr. Cruckshank's wife to be held in her Individual Retirement Account in which Mr. Cruckshank has a beneficial interest.</footnote>
        <footnote id="F3">Includes 63,750 shares held by Mr. Cruckshank directly and 15,000 shares held in Mr. Cruckshank's Individual Retirement Account as well as 15,000 shares held in Mr. Cruckshank's wife's Individual Retirement Account in which Mr. Cruckshank has a beneficial interest.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>James W. Cruckshank</signatureName>
        <signatureDate>2007-08-30</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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