-----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,
 NcKGdeQbX1x4AALiwDA9S5OexlcGFpRRoafIaDzjxsGv5iI8ym7sPeObbPmO5Eo+
 skQSnVZzqHQu6y39pWZwMg==

<SEC-DOCUMENT>0000950172-07-000096.txt : 20070425
<SEC-HEADER>0000950172-07-000096.hdr.sgml : 20070425
<ACCEPTANCE-DATETIME>20070425170717
ACCESSION NUMBER:		0000950172-07-000096
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20070423
FILED AS OF DATE:		20070425
DATE AS OF CHANGE:		20070425

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			BLACKROCK CORE BOND TRUST
		CENTRAL INDEX KEY:			0001160864
		IRS NUMBER:				522346891
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1031

	BUSINESS ADDRESS:	
		STREET 1:		100 BELLEVUE PARKWAY
		STREET 2:		MUTUAL FUND DEPARTMENT
		CITY:			WILMINGTON
		STATE:			DE
		ZIP:			19809
		BUSINESS PHONE:		888-825-2257

	MAIL ADDRESS:	
		STREET 1:		100 BELLEVUE PARKWAY
		STREET 2:		MUTUAL FUND DEPARTMENT
		CITY:			WILMINGTON
		STATE:			DE
		ZIP:			19809

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			FELDSTEIN KATHLEEN F
		CENTRAL INDEX KEY:			0001162744

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	811-10543
		FILM NUMBER:		07788323

	BUSINESS ADDRESS:	
		STREET 1:		147 CLIFTON STREET
		CITY:			BELMONT
		STATE:			MA
		ZIP:			02478
		BUSINESS PHONE:		6179519491
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>primary_doc.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2007-04-23</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001160864</issuerCik>
        <issuerName>BLACKROCK CORE BOND TRUST</issuerName>
        <issuerTradingSymbol>BHK</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001162744</rptOwnerCik>
            <rptOwnerName>FELDSTEIN KATHLEEN F</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O BLACKROCK FINANCIAL MANAGEMENT, INC.</rptOwnerStreet1>
            <rptOwnerStreet2>40 EAST 52ND STREET</rptOwnerStreet2>
            <rptOwnerCity>NEW YORK</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10022</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Performance Rights</value>
                <footnoteId id="F1"/>
            </securityTitle>
            <conversionOrExercisePrice>
                <footnoteId id="F2"/>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2007-04-23</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>371</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>12.86</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F3"/>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F3"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>371</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>1108.82</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">The Phantom Stock units were accrued under the BlackRock Deferred Compensation Plan.</footnote>
        <footnote id="F2">One performance right is convertible into the cash value of one share of BlackRock Core Bond Trust.</footnote>
        <footnote id="F3">The units are to be settled 100% in cash at the deferral period chosen by the reporting person.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Brian P. Kindelan as Attorney-in-Fact</signatureName>
        <signatureDate>2007-04-25</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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