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Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
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 TWSM7vrzLADbmYQaionwg5sDW3P6oaM5D3tdezXMm7z1T+B+twIDAQAB
MIC-Info: RSA-MD5,RSA,
 QtFP6StpbqK9JMmCSe+3klrQqcsCZd1LNNctxkJA9d3LuCx9HRA5A/ye4H+FKB3Z
 6bCWK+t5C2cRhG6D5rdUKw==

<SEC-DOCUMENT>0001179110-03-001032.txt : 20030519
<SEC-HEADER>0001179110-03-001032.hdr.sgml : 20030519
<ACCEPTANCE-DATETIME>20030519110129
ACCESSION NUMBER:		0001179110-03-001032
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20030519
FILED AS OF DATE:		20030519

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			RYAN PATRICK G
		CENTRAL INDEX KEY:			0001145037

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-07933
		FILM NUMBER:		03709923

	BUSINESS ADDRESS:	
		STREET 1:		C/O RYAN ENTERPRISES
		STREET 2:		123 N WACKER DRIVE
		CITY:			CHICAGO
		STATE:			IL
		ZIP:			60606
		BUSINESS PHONE:		3127012300

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 RANDLOPH 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
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>edgar.xml
<DESCRIPTION>FORM 4 -2003-05-19
<TEXT>
<XML>
<?xml version="1.0"?><ownershipDocument><schemaVersion>X0101</schemaVersion>    <documentType>4</documentType><periodOfReport>2003-05-19</periodOfReport><notSubjectToSection16>0</notSubjectToSection16><issuer><issuerCik>0000315293</issuerCik><issuerName>AON CORP</issuerName>        <issuerTradingSymbol>AOC</issuerTradingSymbol></issuer><reportingOwner><reportingOwnerId><rptOwnerCik>0001145037</rptOwnerCik><rptOwnerName>RYAN PATRICK G</rptOwnerName></reportingOwnerId><reportingOwnerAddress><rptOwnerStreet1>  </rptOwnerStreet1><rptOwnerStreet2>  </rptOwnerStreet2><rptOwnerCity>  </rptOwnerCity><rptOwnerState>  </rptOwnerState><rptOwnerZipCode>  </rptOwnerZipCode></reportingOwnerAddress><reportingOwnerRelationship><isDirector>1</isDirector><isOfficer>1</isOfficer><isTenPercentOwner>0</isTenPercentOwner><isOther>0</isOther><officerTitle>Chairman and CEO</officerTitle><otherText></otherText></reportingOwnerRelationship></reportingOwner><nonDerivativeSecurity><securityTitle><value>Common Stock</value></securityTit
le><transactionDate><value>2003-05-15</value></transactionDate><transactionCoding><transactionFormType>4</transactionFormType><transactionCode>M</transactionCode><equitySwapInvolved>0</equitySwapInvolved><footnoteId id="F1"/></transactionCoding><transactionTimeliness><value></value></transactionTimeliness><transactionAmounts><transactionShares><value>216437</value></transactionShares><transactionValue><value>24.82</value></transactionValue><transactionAcquiredDisposedCode><value>A</value></transactionAcquiredDisposedCode></transactionAmounts><postTransactionAmounts><sharesOwnedFollowingTransaction><value>0</value><footnoteId id="F2"/></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership></ownershipNature></nonDerivativeSecurity><nonDerivativeSecurity><securityTitle><value>Common Stock</value></securityTitle><transactionDate><value>2003-05-15</value></transactionDate><transactionCoding><transactionFormType>4</transact
ionFormType><transactionCode>F</transactionCode><equitySwapInvolved>0</equitySwapInvolved><footnoteId id="F3"/></transactionCoding><transactionTimeliness><value></value></transactionTimeliness><transactionAmounts><transactionShares><value>64931</value></transactionShares><transactionValue><value>24.82</value></transactionValue><transactionAcquiredDisposedCode><value>D</value></transactionAcquiredDisposedCode></transactionAmounts><postTransactionAmounts><sharesOwnedFollowingTransaction><value>13111806</value><footnoteId id="F4"/></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership></ownershipNature></nonDerivativeSecurity><derivativeSecurity><securityTitle><value>Phantom Shares</value></securityTitle><conversionOrExercisePrice><value>0</value><footnoteId id="F5"/></conversionOrExercisePrice><transactionDate><value>2003-05-15</value></transactionDate><transactionCoding><transactionFormType>4</transactionFormType><tran
sactionCode>M</transactionCode><equitySwapInvolved>false</equitySwapInvolved></transactionCoding><transactionTimeliness><value></value></transactionTimeliness><transactionAmounts><transactionShares><value>216437</value></transactionShares><transactionValue><value>0</value></transactionValue><transactionAcquiredDisposedCode><value>D</value><footnoteId id="F6"/></transactionAcquiredDisposedCode></transactionAmounts><exerciseDate><value>2003-05-15</value></exerciseDate><expirationDate><value>2003-05-15</value></expirationDate><underlyingSecurity><underlyingSecurityTitle><value>Common Stock</value></underlyingSecurityTitle><underlyingSecurityShares><value>216437</value></underlyingSecurityShares></underlyingSecurity><postTransactionAmounts><sharesOwnedFollowingTransaction><value>0</value></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership></ownershipNature></derivativeSecurity><footnotes><footnote id="F1">Shares of com
mon stock acquired upon conversion of phantom stock.  The phantom stock had been acquired upon the exercise of a stock option and deferral of the receipt of the common stock until May 15, 2003.</footnote><footnote id="F2">See the next line in the table and footnote 4 for total beneficial ownership following all reported transactions.</footnote><footnote id="F3">Shares of common stock withheld by issuer for payment of withholding taxes on the conversion of phantom stock into shares of common stock.</footnote><footnote id="F4">The reporting person also is the indirect beneficial owner of the following securities:  365,876 by ESOP and Savings Plan; 9,951,953 by Spouse; 583,942 by Spouse.</footnote><footnote id="F5">1-for-1</footnote><footnote id="F6">Includes 13,937 phantom shares acquired pursuant to the reimbursement of dividend equivalents.</footnote></footnotes><ownerSignature><signatureName>/s/ Patrick G. Ryan</signatureName><signatureDate>2003-05-19</signatureDate></ownerSignature></ownershipDocument>

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</TEXT>
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</SEC-DOCUMENT>
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