-----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,
 ERnk0pFO2fjHGbHpULnPmVSRSkZSBtjQEAMnJsoQe4Vxc5B41qe5z/Vp469SWL0S
 ejj8/P5pux9xDyFEbmZ40Q==

<SEC-DOCUMENT>0001102624-08-000139.txt : 20080516
<SEC-HEADER>0001102624-08-000139.hdr.sgml : 20080516
<ACCEPTANCE-DATETIME>20080516162112
ACCESSION NUMBER:		0001102624-08-000139
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20080515
FILED AS OF DATE:		20080516
DATE AS OF CHANGE:		20080516

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			PROSPECT CAPITAL CORP
		CENTRAL INDEX KEY:			0001287032
		IRS NUMBER:				432048643
		STATE OF INCORPORATION:			MD
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		10 EAST 40TH STREET 44TH FL
		CITY:			NEW YORK
		STATE:			NY
		ZIP:			10016
		BUSINESS PHONE:		212-448-0702

	MAIL ADDRESS:	
		STREET 1:		10 EAST 40TH STREET 44TH FL
		CITY:			NEW YORK
		STATE:			NY
		ZIP:			10016

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	PROSPECT ENERGY CORP
		DATE OF NAME CHANGE:	20040623

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	PROSPECT STREET ENERGY CORP
		DATE OF NAME CHANGE:	20040414

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Barry John F
		CENTRAL INDEX KEY:			0001294357

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	814-00659
		FILM NUMBER:		08842596

	BUSINESS ADDRESS:	
		BUSINESS PHONE:		212-448-0702

	MAIL ADDRESS:	
		STREET 1:		C/O PROSPECT ENERGY CORPORATION
		STREET 2:		10 EAST 40TH STREET, 44TH FLOOR
		CITY:			NEW YORK
		STATE:			NY
		ZIP:			10016
</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>2008-05-15</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001287032</issuerCik>
        <issuerName>PROSPECT CAPITAL CORP</issuerName>
        <issuerTradingSymbol>PSEC</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001294357</rptOwnerCik>
            <rptOwnerName>Barry John F</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>10 EAST 40TH STREET, 44TH FLOOR</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>NEW YORK</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10016</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>CEO</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2008-05-15</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>5000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>15.3082</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>357668.015</value>
                    <footnoteId id="F1"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Prospect Capital Management</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Prospect Capital Management LLC's purchase of PSEC shares.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>John Barry</signatureName>
        <signatureDate>2008-05-16</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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