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Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
Originator-Key-Asymmetric:
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 TWSM7vrzLADbmYQaionwg5sDW3P6oaM5D3tdezXMm7z1T+B+twIDAQAB
MIC-Info: RSA-MD5,RSA,
 PC+/Pk6kDNyoPRDo+QOUYLyjvymUp5V+graw3t7BI4afcm5yk7Cv3YvhUY2Pgust
 1LmNOISXbkyBVk+NqsLTOA==

<SEC-DOCUMENT>0001179110-03-007751.txt : 20030923
<SEC-HEADER>0001179110-03-007751.hdr.sgml : 20030923
<ACCEPTANCE-DATETIME>20030923125645
ACCESSION NUMBER:		0001179110-03-007751
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20030919
FILED AS OF DATE:		20030923

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			AON CORP
		CENTRAL INDEX KEY:			0000315293
		STANDARD INDUSTRIAL CLASSIFICATION:	ACCIDENT & HEALTH INSURANCE [6321]
		IRS NUMBER:				363051915
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		200 EAST RANDOLPH STREET
		CITY:			CHICAGO
		STATE:			IL
		ZIP:			60601
		BUSINESS PHONE:		3123811000

	MAIL ADDRESS:	
		STREET 1:		200 EAST RANDOLPH STREET
		CITY:			CHICAGO
		STATE:			IL
		ZIP:			60601

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	COMBINED INTERNATIONAL CORP
		DATE OF NAME CHANGE:	19870504

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			NOTEBAERT RICHARD C
		CENTRAL INDEX KEY:			0001112731
		STANDARD INDUSTRIAL CLASSIFICATION:	TELEPHONE & TELEGRAPH APPARATUS [3661]
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			0101

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-07933
		FILM NUMBER:		03905605

	BUSINESS ADDRESS:	
		STREET 1:		4951 INDIANA AVE
		STREET 2:		C/O TELLABS INC
		CITY:			LISLE
		STATE:			IL
		ZIP:			60532
		BUSINESS PHONE:		6303788800

	MAIL ADDRESS:	
		STREET 1:		4951 INDIANA AVE
		STREET 2:		TELLABS INC
		CITY:			LISLE
		STATE:			IL
		ZIP:			60532
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>edgar.xml
<DESCRIPTION>FORM 4 -
<TEXT>
<XML>
<ownershipDocument>
    <schemaVersion>X0201</schemaVersion>

    <documentType>4</documentType>
<periodOfReport>2003-09-19</periodOfReport>
<notSubjectToSection16>0</notSubjectToSection16>
    <issuer>
        <issuerCik>0000315293</issuerCik>
        <issuerName>AON CORP</issuerName>
        <issuerTradingSymbol>AOC</issuerTradingSymbol>
</issuer>
<reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001112731</rptOwnerCik>
            <rptOwnerName>NOTEBAERT RICHARD C</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>AON CORPORATION - CORPORATE LAW DEPT</rptOwnerStreet1>
            <rptOwnerStreet2>200 EAST RANDOLPH STREET, 8TH FLOOR</rptOwnerStreet2>
            <rptOwnerCity>CHICAGO</rptOwnerCity>
            <rptOwnerState>IL</rptOwnerState>
            <rptOwnerZipCode>60601</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
            <reportingOwnerRelationship>
<isDirector>1</isDirector>
<isOfficer>0</isOfficer>
<isTenPercentOwner>0</isTenPercentOwner>
<isOther>0</isOther>
<officerTitle></officerTitle>
<otherText></otherText>
</reportingOwnerRelationship>
</reportingOwner>
<nonDerivativeTable></nonDerivativeTable>
<derivativeTable><derivativeTransaction><securityTitle><value>Phantom Stock</value>
</securityTitle>
<conversionOrExercisePrice><footnoteId id="F1"></footnoteId>
</conversionOrExercisePrice>
<transactionDate><value>2003-09-19</value>
<footnoteId id="F2"></footnoteId>
</transactionDate>
<transactionCoding><transactionFormType>4</transactionFormType>
<transactionCode>A</transactionCode>
<equitySwapInvolved>0</equitySwapInvolved>
</transactionCoding>
<transactionAmounts><transactionShares><value>342.622</value>
</transactionShares>
<transactionPricePerShare><value>21.890</value>
</transactionPricePerShare>
<transactionAcquiredDisposedCode><value>A</value>
</transactionAcquiredDisposedCode>
</transactionAmounts>
<exerciseDate><value>2003-09-19</value>
</exerciseDate>
<expirationDate><footnoteId id="F3"></footnoteId>
</expirationDate>
<underlyingSecurity><underlyingSecurityTitle><value>Common Stock</value>
</underlyingSecurityTitle>
<underlyingSecurityShares><value>342.622</value>
</underlyingSecurityShares>
</underlyingSecurity>
<postTransactionAmounts><sharesOwnedFollowingTransaction><value>5815.057</value>
</sharesOwnedFollowingTransaction>
</postTransactionAmounts>
<ownershipNature><directOrIndirectOwnership><value>D</value>
</directOrIndirectOwnership>
</ownershipNature>
</derivativeTransaction>
</derivativeTable>
<footnotes><footnote id="F1">The phantom stock units convert to common stock on a 1 for 1 basis.</footnote>
<footnote id="F2">The phantom stock units represent an outside director fee that was deferred pursuant to a directors' deferred compensation arrangement.</footnote>
<footnote id="F3">The phantom stock units will be paid in cash or Aon Corporation common stock on a distribution date elected by the reporting person.</footnote>
</footnotes>
<ownerSignature><signatureName>Richard C. Notebaert</signatureName>
<signatureDate>2003-09-23</signatureDate>
</ownerSignature>
</ownershipDocument>

</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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