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Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
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MIC-Info: RSA-MD5,RSA,
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 wEf6yVQO/ru/yhAkyVkbPQ==

<SEC-DOCUMENT>0001447362-09-000007.txt : 20090320
<SEC-HEADER>0001447362-09-000007.hdr.sgml : 20090320
<ACCEPTANCE-DATETIME>20090320162517
ACCESSION NUMBER:		0001447362-09-000007
CONFORMED SUBMISSION TYPE:	D/A
PUBLIC DOCUMENT COUNT:		1
ITEM INFORMATION:		Rule 506
FILED AS OF DATE:		20090320
DATE AS OF CHANGE:		20090320
EFFECTIVENESS DATE:		20090320

FILER:

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			CASTLE BIOSCIENCES INC
		CENTRAL INDEX KEY:			0001447362
		IRS NUMBER:				770701744
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	FILING VALUES:
		FORM TYPE:		D/A
		SEC ACT:		1933 Act
		SEC FILE NUMBER:	021-123250
		FILM NUMBER:		09696580

	BUSINESS ADDRESS:	
		STREET 1:		2014 SAN MIGUEL DR
		CITY:			FRIENDSWOOD
		STATE:			TX
		ZIP:			77546
		BUSINESS PHONE:		281-796-9032

	MAIL ADDRESS:	
		STREET 1:		2014 SAN MIGUEL DR
		CITY:			FRIENDSWOOD
		STATE:			TX
		ZIP:			77546
</SEC-HEADER>
<DOCUMENT>
<TYPE>D/A
<SEQUENCE>1
<FILENAME>primary_doc.xml
<TEXT>
<XML>
<?xml version="1.0"?>
<edgarSubmission>

    <schemaVersion>X0301</schemaVersion>

    <submissionType>D/A</submissionType>

    <testOrLive>LIVE</testOrLive>

    <primaryIssuer>
        <cik>0001447362</cik>
        <entityName>CASTLE BIOSCIENCES INC</entityName>
        <issuerAddress>
            <street1>2014 SAN MIGUEL DR</street1>
            <street2></street2>
            <city>FRIENDSWOOD</city>
            <stateOrCountry>TX</stateOrCountry>
            <zipCode>77546</zipCode>
        </issuerAddress>
        <issuerPhoneNumber>281-796-9032</issuerPhoneNumber>
        <issuerPreviousNameList>
            <value>None</value>
        </issuerPreviousNameList>
        <jurisdictionOfInc>DE</jurisdictionOfInc>
        <entityType>Corporation</entityType>
        <yearOfInc>
            <withinFiveYears>true</withinFiveYears>
            <value>2007</value>
        </yearOfInc>
    </primaryIssuer>

    <relatedPersonsList>
        <relatedPersonInfo>
            <relatedPersonName>
                <firstName>Derek</firstName>
                <middleName>J.</middleName>
                <lastName>Maetzold</lastName>
            </relatedPersonName>
            <relatedPersonAddress>
                <street1>2014 San Miguel Drive</street1>
                <street2></street2>
                <city>Friendswood</city>
                <stateOrCountry>TX</stateOrCountry>
                <zipCode>77546</zipCode>
            </relatedPersonAddress>
            <relatedPersonRelationshipList>
                <relationship>Executive Officer</relationship>
                <relationship>Director</relationship>
                <relationship>Promoter</relationship>
            </relatedPersonRelationshipList>
            <relationshipClarification></relationshipClarification>
        </relatedPersonInfo>
    </relatedPersonsList>

    <offeringData>
        <industryGroup>
            <industryGroupType>Biotechnology</industryGroupType>
        </industryGroup>
        <issuerSize>
            <revenueRange>Decline to Disclose</revenueRange>
        </issuerSize>
        <federalExemptionsExclusions>
            <item>06</item>
        </federalExemptionsExclusions>
        <typeOfFiling>
            <newOrAmendment>
                <isAmendment>true</isAmendment>
                <previousAccessionNumber>9999999997-08-041882</previousAccessionNumber>
            </newOrAmendment>
            <dateOfFirstSale>
                <value>2008-09-12</value>
            </dateOfFirstSale>
        </typeOfFiling>
        <durationOfOffering>
            <moreThanOneYear>false</moreThanOneYear>
        </durationOfOffering>
        <typesOfSecuritiesOffered>
            <isEquityType>true</isEquityType>
            <isOptionToAcquireType>true</isOptionToAcquireType>
            <isSecurityToBeAcquiredType>true</isSecurityToBeAcquiredType>
        </typesOfSecuritiesOffered>
        <businessCombinationTransaction>
            <isBusinessCombinationTransaction>false</isBusinessCombinationTransaction>
            <clarificationOfResponse></clarificationOfResponse>
        </businessCombinationTransaction>
        <minimumInvestmentAccepted>0</minimumInvestmentAccepted>
        <salesCompensationList></salesCompensationList>
        <offeringSalesAmounts>
            <totalOfferingAmount>1280717</totalOfferingAmount>
            <totalAmountSold>935899</totalAmountSold>
            <totalRemaining>344818</totalRemaining>
            <clarificationOfResponse>$231,241.98 of the Aggregate Offering Price has not been received by the Issuer to date and will not be received until such time, if any, that all of the Warrants that are authorized in this offering are exercised.</clarificationOfResponse>
        </offeringSalesAmounts>
        <investors>
            <hasNonAccreditedInvestors>false</hasNonAccreditedInvestors>
            <totalNumberAlreadyInvested>11</totalNumberAlreadyInvested>
        </investors>
        <salesCommissionsFindersFees>
            <salesCommissions>
                <dollarAmount>0</dollarAmount>
            </salesCommissions>
            <findersFees>
                <dollarAmount>0</dollarAmount>
            </findersFees>
            <clarificationOfResponse></clarificationOfResponse>
        </salesCommissionsFindersFees>
        <useOfProceeds>
            <grossProceedsUsed>
                <dollarAmount>0</dollarAmount>
            </grossProceedsUsed>
            <clarificationOfResponse></clarificationOfResponse>
        </useOfProceeds>
        <signatureBlock>
            <authorizedRepresentative>false</authorizedRepresentative>
            <signature>
                <issuerName>CASTLE BIOSCIENCES INC</issuerName>
                <signatureName>/s/ Derek J. Maetzold</signatureName>
                <nameOfSigner>Derk J. Maetzold</nameOfSigner>
                <signatureTitle>President &amp; CEO</signatureTitle>
                <signatureDate>2009-03-20</signatureDate>
            </signature>
        </signatureBlock>
    </offeringData>
</edgarSubmission>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
-----END PRIVACY-ENHANCED MESSAGE-----
