-----BEGIN PRIVACY-ENHANCED MESSAGE-----
Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
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MIC-Info: RSA-MD5,RSA,
 C1WuUjhw+NNmSFYM6FR5DnO+arvPafh7gSp4d65jDuKTH8qtTGIzulPGGISD+mNY
 N99NPALUmHYWkmJJHIeBiA==

<SEC-DOCUMENT>0001198929-03-000088.txt : 20030722
<SEC-HEADER>0001198929-03-000088.hdr.sgml : 20030722
<ACCEPTANCE-DATETIME>20030722140933
ACCESSION NUMBER:		0001198929-03-000088
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20030718
FILED AS OF DATE:		20030722

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			PETROCORP INC
		CENTRAL INDEX KEY:			0000911359
		STANDARD INDUSTRIAL CLASSIFICATION:	CRUDE PETROLEUM & NATURAL GAS [1311]
		IRS NUMBER:				760380430
		STATE OF INCORPORATION:			TX
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		6733 SOUTH YALE
		CITY:			TULSA
		STATE:			OK
		ZIP:			74136-2391
		BUSINESS PHONE:		7138752500

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			ST PAUL COMPANIES INC /MN/
		CENTRAL INDEX KEY:			0000086312
		STANDARD INDUSTRIAL CLASSIFICATION:	FIRE, MARINE & CASUALTY INSURANCE [6331]
		STATE OF INCORPORATION:			MN
		FISCAL YEAR END:			1231

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-14459
		FILM NUMBER:		03796181

	BUSINESS ADDRESS:	
		STREET 1:		385 WASHINGTON ST
		CITY:			SAINT PAUL
		STATE:			MN
		ZIP:			55102
		BUSINESS PHONE:		6123107911

	FORMER NAME:	
		FORMER CONFORMED NAME:	ST PAUL FIRE & MARINE INSURANCE CO/MD
		DATE OF NAME CHANGE:	19990219

	FORMER NAME:	
		FORMER CONFORMED NAME:	ST PAUL COMPANIES INC/MN/
		DATE OF NAME CHANGE:	19990219

	FORMER NAME:	
		FORMER CONFORMED NAME:	SAINT PAUL COMPANIES INC
		DATE OF NAME CHANGE:	19900730
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>primary_doc.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>

<ownershipDocument>

    <documentType>4</documentType>

    <periodOfReport>2003-07-18</periodOfReport>


    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000911359</issuerCik>
        <issuerName>PETROCORP INC</issuerName>
        <issuerTradingSymbol>PEX</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0000086312</rptOwnerCik>
            <rptOwnerName>ST PAUL COMPANIES INC /MN/</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>  </rptOwnerStreet1>
            <rptOwnerStreet2>  </rptOwnerStreet2>
            <rptOwnerCity>  </rptOwnerCity>
            <rptOwnerState>  </rptOwnerState>
            <rptOwnerZipCode>  </rptOwnerZipCode>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeSecurity>
        <securityTitle>
            <value>Common Stock</value>
        </securityTitle>
        <transactionDate>
            <value>2003-07-18</value>
        </transactionDate>
        <transactionCoding>
            <transactionFormType>4</transactionFormType>
            <transactionCode>S</transactionCode>
            <equitySwapInvolved>0</equitySwapInvolved>
        </transactionCoding>
        <transactionTimeliness>
            <value></value>
        </transactionTimeliness>
        <transactionAmounts>
            <transactionShares>
                <value>22876</value>
            </transactionShares>
            <transactionValue>
                <value>14.0596</value>
            </transactionValue>
            <transactionAcquiredDisposedCode>
                <value>D</value>
            </transactionAcquiredDisposedCode>
        </transactionAmounts>
        <postTransactionAmounts>
            <sharesOwnedFollowingTransaction>
                <value>1708124</value>
            </sharesOwnedFollowingTransaction>
        </postTransactionAmounts>
        <ownershipNature>
            <directOrIndirectOwnership>
                <value>I</value>
            </directOrIndirectOwnership>
            <natureOfOwnership>
                <value>Through a wholly owned subsidiary</value>
                <footnoteId id="F1"/>
            </natureOfOwnership>
        </ownershipNature>
    </nonDerivativeSecurity>

    <nonDerivativeSecurity>
        <securityTitle>
            <value>Common Stock</value>
        </securityTitle>
        <transactionDate>
            <value>2003-07-21</value>
        </transactionDate>
        <transactionCoding>
            <transactionFormType>4</transactionFormType>
            <transactionCode>S</transactionCode>
            <equitySwapInvolved>0</equitySwapInvolved>
        </transactionCoding>
        <transactionTimeliness>
            <value></value>
        </transactionTimeliness>
        <transactionAmounts>
            <transactionShares>
                <value>25500</value>
            </transactionShares>
            <transactionValue>
                <value>14.1341</value>
            </transactionValue>
            <transactionAcquiredDisposedCode>
                <value>D</value>
            </transactionAcquiredDisposedCode>
        </transactionAmounts>
        <postTransactionAmounts>
            <sharesOwnedFollowingTransaction>
                <value>1682624</value>
            </sharesOwnedFollowingTransaction>
        </postTransactionAmounts>
        <ownershipNature>
            <directOrIndirectOwnership>
                <value>I</value>
            </directOrIndirectOwnership>
            <natureOfOwnership>
                <value>Through a wholly owned subsidiary</value>
                <footnoteId id="F1"/>
            </natureOfOwnership>
        </ownershipNature>
    </nonDerivativeSecurity>

    <footnotes>
        <footnote id="F1">On April 27 1998, St. Paul Fire and Marine Insurance Company, a wholly owned subsidiary of The St. Paul Companies, Inc., acquired substantially all of the assets of United States Fidelity and Guaranty Company, such assets including 1,731,000 shares of PetroCorp, Inc.  United States Fidelity and Guaranty Company acquired the PetroCorp, Inc. shares prior to 1998.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Bruce A. Backberg</signatureName>
        <signatureDate>2003-07-22</signatureDate>
    </ownerSignature>

</ownershipDocument>

</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
-----END PRIVACY-ENHANCED MESSAGE-----