-----BEGIN PRIVACY-ENHANCED MESSAGE-----
Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
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MIC-Info: RSA-MD5,RSA,
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 B6uOEX7DxNIlYiRLHuW10Q==

<SEC-DOCUMENT>0001002910-03-000244.txt : 20030520
<SEC-HEADER>0001002910-03-000244.hdr.sgml : 20030520
<ACCEPTANCE-DATETIME>20030520155445
ACCESSION NUMBER:		0001002910-03-000244
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20030331
FILED AS OF DATE:		20030520

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			CORNELIUS WILLIAM E
		CENTRAL INDEX KEY:			0001013054
		STANDARD INDUSTRIAL CLASSIFICATION:	AIRCRAFT [3721]
		STATE OF INCORPORATION:			MD
		FISCAL YEAR END:			1231

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-14756
		FILM NUMBER:		03712548

	BUSINESS ADDRESS:	
		STREET 1:		P O BOX 516
		STREET 2:		MCDONNELL BLVD AT AIRPORT RD
		CITY:			ST LOUIS
		STATE:			MO
		ZIP:			63166-0516
		BUSINESS PHONE:		3142320232

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			AMEREN CORP
		CENTRAL INDEX KEY:			0001002910
		STANDARD INDUSTRIAL CLASSIFICATION:	ELECTRIC & OTHER SERVICES COMBINED [4931]
		IRS NUMBER:				431723446
		STATE OF INCORPORATION:			MO
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		1901 CHOUTEAU AVE
		STREET 2:		MC 1370
		CITY:			ST LOUIS
		STATE:			MO
		ZIP:			63166-6149
		BUSINESS PHONE:		431723446

	MAIL ADDRESS:	
		STREET 1:		1901 CHOUTEAU AVE
		STREET 2:		MC 1370
		CITY:			ST LOUIS
		STATE:			MO
		ZIP:			63103
</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>2003-03-31</periodOfReport>


    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001002910</issuerCik>
        <issuerName>AMEREN CORP</issuerName>
        <issuerTradingSymbol>AEE</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001013054</rptOwnerCik>
            <rptOwnerName>CORNELIUS WILLIAM E</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>  </rptOwnerStreet1>
            <rptOwnerStreet2>  </rptOwnerStreet2>
            <rptOwnerCity>  </rptOwnerCity>
            <rptOwnerState>  </rptOwnerState>
            <rptOwnerZipCode>  </rptOwnerZipCode>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeSecurity>
        <securityTitle>
            <value>Common Stock, $.01 Par Value</value>
        </securityTitle>
        <transactionDate>
            <value>2003-03-31</value>
        </transactionDate>
        <transactionCoding>
            <transactionFormType>5</transactionFormType>
            <transactionCode>L</transactionCode>
            <equitySwapInvolved>0</equitySwapInvolved>
        </transactionCoding>
        <transactionTimeliness>
            <value>E</value>
        </transactionTimeliness>
        <transactionAmounts>
            <transactionShares>
                <value>63</value>
            </transactionShares>
            <transactionValue>
                <value>39.045</value>
            </transactionValue>
            <transactionAcquiredDisposedCode>
                <value>A</value>
            </transactionAcquiredDisposedCode>
        </transactionAmounts>
        <postTransactionAmounts>
            <sharesOwnedFollowingTransaction>
                <value>4454</value>
            </sharesOwnedFollowingTransaction>
        </postTransactionAmounts>
        <ownershipNature>
            <directOrIndirectOwnership>
                <value>D</value>
            </directOrIndirectOwnership>
        </ownershipNature>
    </nonDerivativeSecurity>

    <nonDerivativeSecurity>
        <securityTitle>
            <value>Common Stock, $.01 Par Value</value>
        </securityTitle>
        <transactionDate>
            <value>2003-03-31</value>
        </transactionDate>
        <transactionCoding>
            <transactionFormType>5</transactionFormType>
            <transactionCode>L</transactionCode>
            <equitySwapInvolved>0</equitySwapInvolved>
        </transactionCoding>
        <transactionTimeliness>
            <value>E</value>
        </transactionTimeliness>
        <transactionAmounts>
            <transactionShares>
                <value>2</value>
                <footnoteId id="F1"/>
            </transactionShares>
            <transactionValue>
                <value>39.045</value>
            </transactionValue>
            <transactionAcquiredDisposedCode>
                <value>A</value>
            </transactionAcquiredDisposedCode>
        </transactionAmounts>
        <postTransactionAmounts>
            <sharesOwnedFollowingTransaction>
                <value>125</value>
            </sharesOwnedFollowingTransaction>
        </postTransactionAmounts>
        <ownershipNature>
            <directOrIndirectOwnership>
                <value>I</value>
            </directOrIndirectOwnership>
            <natureOfOwnership>
                <value>Spouse as Trustee for Grandchild #1</value>
            </natureOfOwnership>
        </ownershipNature>
    </nonDerivativeSecurity>

    <nonDerivativeSecurity>
        <securityTitle>
            <value>Common Stock, $.01 Par Value</value>
        </securityTitle>
        <transactionDate>
            <value>2003-05-15</value>
        </transactionDate>
        <transactionCoding>
            <transactionFormType>4</transactionFormType>
            <transactionCode>A</transactionCode>
            <equitySwapInvolved>0</equitySwapInvolved>
        </transactionCoding>
        <transactionTimeliness>
            <value></value>
        </transactionTimeliness>
        <transactionAmounts>
            <transactionShares>
                <value>119</value>
            </transactionShares>
            <transactionValue>
                <value>42.06</value>
            </transactionValue>
            <transactionAcquiredDisposedCode>
                <value>A</value>
            </transactionAcquiredDisposedCode>
        </transactionAmounts>
        <postTransactionAmounts>
            <sharesOwnedFollowingTransaction>
                <value>244</value>
            </sharesOwnedFollowingTransaction>
        </postTransactionAmounts>
        <ownershipNature>
            <directOrIndirectOwnership>
                <value>I</value>
            </directOrIndirectOwnership>
            <natureOfOwnership>
                <value>Spouse as Trustee for Grandchild #1</value>
            </natureOfOwnership>
        </ownershipNature>
    </nonDerivativeSecurity>

    <nonDerivativeSecurity>
        <securityTitle>
            <value>Common Stock, $.01 Par Value</value>
        </securityTitle>
        <transactionDate>
            <value>2003-03-31</value>
        </transactionDate>
        <transactionCoding>
            <transactionFormType>5</transactionFormType>
            <transactionCode>L</transactionCode>
            <equitySwapInvolved>0</equitySwapInvolved>
        </transactionCoding>
        <transactionTimeliness>
            <value>E</value>
        </transactionTimeliness>
        <transactionAmounts>
            <transactionShares>
                <value>2</value>
                <footnoteId id="F1"/>
            </transactionShares>
            <transactionValue>
                <value>39.045</value>
            </transactionValue>
            <transactionAcquiredDisposedCode>
                <value>A</value>
            </transactionAcquiredDisposedCode>
        </transactionAmounts>
        <postTransactionAmounts>
            <sharesOwnedFollowingTransaction>
                <value>125</value>
            </sharesOwnedFollowingTransaction>
        </postTransactionAmounts>
        <ownershipNature>
            <directOrIndirectOwnership>
                <value>I</value>
            </directOrIndirectOwnership>
            <natureOfOwnership>
                <value>Spouse as Trustee for Grandchild #2</value>
            </natureOfOwnership>
        </ownershipNature>
    </nonDerivativeSecurity>

    <nonDerivativeSecurity>
        <securityTitle>
            <value>Common Stock, $.01 Par Value</value>
        </securityTitle>
        <transactionDate>
            <value>2003-05-15</value>
        </transactionDate>
        <transactionCoding>
            <transactionFormType>4</transactionFormType>
            <transactionCode>A</transactionCode>
            <equitySwapInvolved>0</equitySwapInvolved>
        </transactionCoding>
        <transactionTimeliness>
            <value></value>
        </transactionTimeliness>
        <transactionAmounts>
            <transactionShares>
                <value>119</value>
            </transactionShares>
            <transactionValue>
                <value>42.06</value>
            </transactionValue>
            <transactionAcquiredDisposedCode>
                <value>A</value>
            </transactionAcquiredDisposedCode>
        </transactionAmounts>
        <postTransactionAmounts>
            <sharesOwnedFollowingTransaction>
                <value>244</value>
            </sharesOwnedFollowingTransaction>
        </postTransactionAmounts>
        <ownershipNature>
            <directOrIndirectOwnership>
                <value>I</value>
            </directOrIndirectOwnership>
            <natureOfOwnership>
                <value>Spouse as Trustee for Grandchild #2</value>
            </natureOfOwnership>
        </ownershipNature>
    </nonDerivativeSecurity>

    <nonDerivativeSecurity>
        <securityTitle>
            <value>Common Stock, $.01 Par Value</value>
        </securityTitle>
        <transactionDate>
            <value>2003-03-31</value>
        </transactionDate>
        <transactionCoding>
            <transactionFormType>5</transactionFormType>
            <transactionCode>L</transactionCode>
            <equitySwapInvolved>0</equitySwapInvolved>
        </transactionCoding>
        <transactionTimeliness>
            <value>E</value>
        </transactionTimeliness>
        <transactionAmounts>
            <transactionShares>
                <value>2</value>
                <footnoteId id="F1"/>
            </transactionShares>
            <transactionValue>
                <value>39.045</value>
            </transactionValue>
            <transactionAcquiredDisposedCode>
                <value>A</value>
            </transactionAcquiredDisposedCode>
        </transactionAmounts>
        <postTransactionAmounts>
            <sharesOwnedFollowingTransaction>
                <value>125</value>
            </sharesOwnedFollowingTransaction>
        </postTransactionAmounts>
        <ownershipNature>
            <directOrIndirectOwnership>
                <value>I</value>
            </directOrIndirectOwnership>
            <natureOfOwnership>
                <value>Spouse as Trustee for Grandchild #3</value>
            </natureOfOwnership>
        </ownershipNature>
    </nonDerivativeSecurity>

    <nonDerivativeSecurity>
        <securityTitle>
            <value>Common Stock, $.01 Par Value</value>
        </securityTitle>
        <transactionDate>
            <value>2003-05-15</value>
        </transactionDate>
        <transactionCoding>
            <transactionFormType>4</transactionFormType>
            <transactionCode>A</transactionCode>
            <equitySwapInvolved>0</equitySwapInvolved>
        </transactionCoding>
        <transactionTimeliness>
            <value></value>
        </transactionTimeliness>
        <transactionAmounts>
            <transactionShares>
                <value>119</value>
            </transactionShares>
            <transactionValue>
                <value>42.06</value>
            </transactionValue>
            <transactionAcquiredDisposedCode>
                <value>A</value>
            </transactionAcquiredDisposedCode>
        </transactionAmounts>
        <postTransactionAmounts>
            <sharesOwnedFollowingTransaction>
                <value>244</value>
            </sharesOwnedFollowingTransaction>
        </postTransactionAmounts>
        <ownershipNature>
            <directOrIndirectOwnership>
                <value>I</value>
            </directOrIndirectOwnership>
            <natureOfOwnership>
                <value>Spouse as Trustee for Grandchild #3</value>
            </natureOfOwnership>
        </ownershipNature>
    </nonDerivativeSecurity>

    <nonDerivativeSecurity>
        <securityTitle>
            <value>Common Stock, $.01 Par Value</value>
        </securityTitle>
        <transactionDate>
            <value>2003-03-31</value>
        </transactionDate>
        <transactionCoding>
            <transactionFormType>5</transactionFormType>
            <transactionCode>L</transactionCode>
            <equitySwapInvolved>0</equitySwapInvolved>
        </transactionCoding>
        <transactionTimeliness>
            <value>E</value>
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        <transactionAmounts>
            <transactionShares>
                <value>2</value>
                <footnoteId id="F1"/>
            </transactionShares>
            <transactionValue>
                <value>39.045</value>
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            <transactionAcquiredDisposedCode>
                <value>A</value>
            </transactionAcquiredDisposedCode>
        </transactionAmounts>
        <postTransactionAmounts>
            <sharesOwnedFollowingTransaction>
                <value>125</value>
            </sharesOwnedFollowingTransaction>
        </postTransactionAmounts>
        <ownershipNature>
            <directOrIndirectOwnership>
                <value>I</value>
            </directOrIndirectOwnership>
            <natureOfOwnership>
                <value>Spouse as Trustee for Grandchild #4</value>
            </natureOfOwnership>
        </ownershipNature>
    </nonDerivativeSecurity>

    <nonDerivativeSecurity>
        <securityTitle>
            <value>Common Stock, $.01 Par Value</value>
        </securityTitle>
        <transactionDate>
            <value>2003-05-15</value>
        </transactionDate>
        <transactionCoding>
            <transactionFormType>4</transactionFormType>
            <transactionCode>A</transactionCode>
            <equitySwapInvolved>0</equitySwapInvolved>
        </transactionCoding>
        <transactionTimeliness>
            <value></value>
        </transactionTimeliness>
        <transactionAmounts>
            <transactionShares>
                <value>119</value>
            </transactionShares>
            <transactionValue>
                <value>42.06</value>
            </transactionValue>
            <transactionAcquiredDisposedCode>
                <value>A</value>
            </transactionAcquiredDisposedCode>
        </transactionAmounts>
        <postTransactionAmounts>
            <sharesOwnedFollowingTransaction>
                <value>244</value>
            </sharesOwnedFollowingTransaction>
        </postTransactionAmounts>
        <ownershipNature>
            <directOrIndirectOwnership>
                <value>I</value>
            </directOrIndirectOwnership>
            <natureOfOwnership>
                <value>Spouse as Trustee for Grandchild #4</value>
            </natureOfOwnership>
        </ownershipNature>
    </nonDerivativeSecurity>

    <nonDerivativeSecurity>
        <securityTitle>
            <value>Common Stock, $.01 Par Value</value>
        </securityTitle>
        <transactionDate>
            <value>2003-03-31</value>
        </transactionDate>
        <transactionCoding>
            <transactionFormType>5</transactionFormType>
            <transactionCode>L</transactionCode>
            <equitySwapInvolved>0</equitySwapInvolved>
        </transactionCoding>
        <transactionTimeliness>
            <value>E</value>
        </transactionTimeliness>
        <transactionAmounts>
            <transactionShares>
                <value>2</value>
                <footnoteId id="F1"/>
            </transactionShares>
            <transactionValue>
                <value>39.045</value>
            </transactionValue>
            <transactionAcquiredDisposedCode>
                <value>A</value>
            </transactionAcquiredDisposedCode>
        </transactionAmounts>
        <postTransactionAmounts>
            <sharesOwnedFollowingTransaction>
                <value>125</value>
            </sharesOwnedFollowingTransaction>
        </postTransactionAmounts>
        <ownershipNature>
            <directOrIndirectOwnership>
                <value>I</value>
            </directOrIndirectOwnership>
            <natureOfOwnership>
                <value>Spouse as Trustee for Grandchild #5</value>
            </natureOfOwnership>
        </ownershipNature>
    </nonDerivativeSecurity>

    <nonDerivativeSecurity>
        <securityTitle>
            <value>Common Stock, $.01 Par Value</value>
        </securityTitle>
        <transactionDate>
            <value>2003-05-15</value>
        </transactionDate>
        <transactionCoding>
            <transactionFormType>5</transactionFormType>
            <transactionCode>L</transactionCode>
            <equitySwapInvolved>0</equitySwapInvolved>
        </transactionCoding>
        <transactionTimeliness>
            <value>E</value>
        </transactionTimeliness>
        <transactionAmounts>
            <transactionShares>
                <value>119</value>
            </transactionShares>
            <transactionValue>
                <value>42.06</value>
            </transactionValue>
            <transactionAcquiredDisposedCode>
                <value>A</value>
            </transactionAcquiredDisposedCode>
        </transactionAmounts>
        <postTransactionAmounts>
            <sharesOwnedFollowingTransaction>
                <value>244</value>
            </sharesOwnedFollowingTransaction>
        </postTransactionAmounts>
        <ownershipNature>
            <directOrIndirectOwnership>
                <value>I</value>
            </directOrIndirectOwnership>
            <natureOfOwnership>
                <value>Spouse as Trustee for Grandchild #5</value>
            </natureOfOwnership>
        </ownershipNature>
    </nonDerivativeSecurity>

    <footnotes>
        <footnote id="F1">Stock was acquired during the first quarter of 2003 through reinvested dividends.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ G. L. Waters, Asst. Secy. for William E. Cornelius</signatureName>
        <signatureDate>2003-05-20</signatureDate>
    </ownerSignature>

</ownershipDocument>

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