-----BEGIN PRIVACY-ENHANCED MESSAGE-----
Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
Originator-Key-Asymmetric:
 MFgwCgYEVQgBAQICAf8DSgAwRwJAW2sNKK9AVtBzYZmr6aGjlWyK3XmZv3dTINen
 TWSM7vrzLADbmYQaionwg5sDW3P6oaM5D3tdezXMm7z1T+B+twIDAQAB
MIC-Info: RSA-MD5,RSA,
 QoYNKj7X3vKw59d7G1dwDB49kfV0d58KdlvFOgvYS+UKT+3q1N/l7vbPpUPBgXJi
 ZYKfaNO7FrqqXitdbMvROA==

<SEC-DOCUMENT>0001002910-03-000254.txt : 20030528
<SEC-HEADER>0001002910-03-000254.hdr.sgml : 20030528
<ACCEPTANCE-DATETIME>20030528103755
ACCESSION NUMBER:		0001002910-03-000254
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20030527
FILED AS OF DATE:		20030528

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			MONTANA MICHAEL J
		CENTRAL INDEX KEY:			0001190106

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-14756
		FILM NUMBER:		03720900

	BUSINESS ADDRESS:	
		BUSINESS PHONE:		314 554 2715

	MAIL ADDRESS:	
		STREET 1:		1901 CHOUTEAU AVENUE MC-1370
		CITY:			ST. LOUIS
		STATE:			MO
		ZIP:			63103

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>edgar.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>
    <schemaVersion>X0101</schemaVersion>

    <documentType>4</documentType><periodOfReport>2003-05-27</periodOfReport>
    <issuer>
        <issuerCik>0001002910</issuerCik>
        <issuerName>AMEREN CORP</issuerName>
        <issuerTradingSymbol>AEE</issuerTradingSymbol></issuer><reportingOwner><reportingOwnerId>
            <rptOwnerCik>0001190106</rptOwnerCik>
            <rptOwnerName>MONTANA MICHAEL J</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>  </rptOwnerStreet1>
            <rptOwnerStreet2>  </rptOwnerStreet2>
            <rptOwnerCity>  </rptOwnerCity>
            <rptOwnerState>  </rptOwnerState>
            <rptOwnerZipCode>  </rptOwnerZipCode>
        </reportingOwnerAddress>
            <reportingOwnerRelationship>
<isDirector>0</isDirector><isOfficer>0</isOfficer><isTenPercentOwner>0</isTenPercentOwner><isOther>1</isOther><otherText>Former VP of Subsidiary</otherText></reportingOwnerRelationship></reportingOwner><nonDerivativeSecurity><securityTitle><value>Common Stock, $.01 Par Value</value></securityTitle><transactionDate><value>2003-05-27</value></transactionDate><transactionCoding><transactionFormType>4</transactionFormType><transactionCode>M</transactionCode><equitySwapInvolved>0</equitySwapInvolved></transactionCoding><transactionAmounts><transactionShares><value>625</value></transactionShares><transactionValue><value>43</value></transactionValue><transactionAcquiredDisposedCode><value>A</value></transactionAcquiredDisposedCode></transactionAmounts><postTransactionAmounts><sharesOwnedFollowingTransaction><value>625</value></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value></value></natureOfOw
nership></ownershipNature></nonDerivativeSecurity><nonDerivativeSecurity><securityTitle><value>Common Stock, $.01 Par Value</value></securityTitle><transactionDate><value>2003-05-27</value></transactionDate><transactionCoding><transactionFormType>4</transactionFormType><transactionCode>S</transactionCode><equitySwapInvolved>0</equitySwapInvolved></transactionCoding><transactionAmounts><transactionShares><value>625</value></transactionShares><transactionValue><value>45.76</value></transactionValue><transactionAcquiredDisposedCode><value>D</value></transactionAcquiredDisposedCode></transactionAmounts><postTransactionAmounts><sharesOwnedFollowingTransaction><value>0</value></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value></value></natureOfOwnership></ownershipNature></nonDerivativeSecurity><derivativeSecurity><securityTitle><value>Stock Option</value></securityTitle><conversionOrExercisePr
ice><value>43</value></conversionOrExercisePrice><transactionDate><value>2003-05-27</value></transactionDate><transactionCoding><transactionFormType>4</transactionFormType><transactionCode>M</transactionCode><equitySwapInvolved>0</equitySwapInvolved></transactionCoding><transactionAmounts><transactionShares><value>625</value></transactionShares><transactionValue><value>45.76</value></transactionValue><transactionAcquiredDisposedCode><value>D</value></transactionAcquiredDisposedCode></transactionAmounts><exerciseDate><value>2002-02-07</value></exerciseDate><expirationDate><value>2006-02-07</value></expirationDate><underlyingSecurity><underlyingSecurityTitle><value>Common Stock, $.01 Par Value</value></underlyingSecurityTitle><underlyingSecurityShares><value>625</value></underlyingSecurityShares></underlyingSecurity><postTransactionAmounts><sharesOwnedFollowingTransaction><value>0</value></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></dir
ectOrIndirectOwnership><natureOfOwnership><value></value></natureOfOwnership></ownershipNature></derivativeSecurity><footnotes/><ownerSignature><signatureName>G. L. Waters, Asst. Secy. for M. J. Montana</signatureName><signatureDate>2003-05-28</signatureDate></ownerSignature></ownershipDocument>

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