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SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549
FORM 10-K

(Mark One)

[X] ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE
SECURITIES EXCHANGE ACT OF 1934 [NO FEE REQUIRED]
For the fiscal year ended December 31, 1999
OR
[ ] TRANSITION REPORT PURSUANT TO SECTION 13 OR 15 (d) OF THE
SECURITIES EXCHANGE ACT OF 1934 [NO FEE REQUIRED]
Commission File Number: 1-7933

Aon Corporation
(Exact Name of Registrant as Specified in its Charter)

DELAWARE
(State or Other Jurisdiction of 36-3051915
Incorporation or Organization) (I.R.S. Employer
123 NORTH WACKER DRIVE, Identification No.)
CHICAGO, ILLINOIS 60606
(Address of Principal Executive Offices) (Zip Code)
(312) 701-3000
(Telephone Number)

Securities registered pursuant to Section 12(b) of the Act:
Name of Each Exchange
Title of Each Class on Which Registered
------------------- -------------------
Common Stock, $1 par value New York Stock Exchange*
7.40% Notes Due 2002 New York Stock Exchange

Securities registered pursuant to Section 12(g) of the Act: NONE

*The Common Stock of the Registrant is also listed for trading on the Chicago
Stock Exchange and the International Stock Exchange London.


Indicate by check mark whether the Registrant (1) has filed all reports required
to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during
the preceding 12 months (or for such shorter period that the Registrant was
required to file such reports), and (2) has been subject to such filing
requirements for the past 90 days. YES [X] NO [ ]


Indicate by check mark if disclosure of delinquent filers pursuant to Item 405
of Regulation S-K is not contained herein, and will not be contained, to the
best of Registrant's knowledge, in definitive proxy or information statements,
incorporated by reference in Part III of this Form 10-K or any amendment to
this Form 10-K. [X]

Aggregate market value of the voting stock held by non-affiliates of the
Registrant as of February 23, 2000 was $5,042,411,250.

Number of shares of $1.00 par value Common Stock outstanding as of February 23,
2000 was 256,453,450.

DOCUMENTS FROM WHICH INFORMATION IS INCORPORATED BY REFERENCE:
Annual Report to Stockholders of the Registrant for the Year 1999
(Parts I, II and IV)
Notice of Annual Meeting of Holders of Common Stock and Series C Preferred
Stock and Proxy Statement for Annual Meeting of Stockholders on April 18, 2000
of the Registrant (Part III)

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PART I

ITEM 1. BUSINESS.

The Registrant is a holding company whose operating subsidiaries carry on
business in three distinct segments: (i) insurance brokerage and other services,
(ii) consulting, and (iii) insurance underwriting. Incorporated in 1979, it is
the parent corporation of long-established and more recently formed companies.

The Insurance Brokerage and Other Services segment consists principally of
Aon's retail and reinsurance brokerage operations, which includes specialty and
wholesale activity. These services are provided by Aon Group, Inc., its
subsidiaries and certain other indirect subsidiaries of the Registrant (the "Aon
Group") including Aon Risk Services Companies, Inc.; Aon Holdings bv; Aon
Services Group, Inc.; Aon Re Worldwide, Inc.; Aon Group Limited; and Alternative
Market Operations ("AMO").

The Consulting segment provides a range of consulting services including
employee benefits, human resources, compensation and change management. These
services are provided by Aon Consulting Worldwide, Inc. which is also a
subsidiary of Aon Group.

Aon Group revenues grew significantly in 1997, 1998 and 1999 when the
Registrant acquired, among other companies, Alexander & Alexander Services
Inc. ("A&A"), The Minet Group, and Jauch & Hubener in 1997; Le Blanc de
Nicolay, Gil y Carvajal and Auto Insurance Specialists, Inc. in 1998; and the
Nikols Group, Presidium Holdings, Inc. and Societe Generale d' Assurance et de
Prevoganie in 1999.

Aon's Insurance Underwriting segment is comprised of direct sales life
and accident and health insurance, extended warranty, specialty and other
insurance products. Combined Insurance Company of America ("Combined Insurance")
engages in the marketing and underwriting of life and accident and health
insurance products. Virginia Surety Company, Inc. and London General Insurance
Company Limited offer extended warranty and specialty insurance products.

The Registrant hereby incorporates by reference pages 8 through 17, 19
through 21, and pages 49 and 50 of the Annual Report to Stockholders of the
Registrant for the Year 1999 ("Annual Report").


COMPETITION AND INDUSTRY POSITION

(1) INSURANCE BROKERAGE AND OTHER SERVICES

Aon Group, Inc. ("Aon Group"); Aon Risk Services Companies, Inc. ("Aon
Risk Services Companies"); Aon Holdings bv ("Aon Holdings"); Aon Services
Group, Inc. ("Aon Services Group"); Aon Re Worldwide, Inc. ("Aon Re"); Aon
Group Limited ("AGL"); Alternative Market Operations ("AMO").

Aon Group is the holding company for the subsidiaries which conduct the
Registrant's commercial brokerage and consulting operations. Aon Group companies
have 550 offices around the world in 120 countries. In 1999, Aon Group employed
over 39,000 professionals and support personnel to serve the diverse needs of
clients.

Aon Risk Services Companies' subsidiaries operate in a highly competitive
industry and compete with a large number of retail insurance brokerage and
agency firms as well as individual brokers and agents and direct writers of
insurance coverage. Aon Risk Services Companies' subsidiaries provide risk
management services, including insurance placement, claims management, loss
control and administrative services. It has also developed certain specialist
niche areas such as marine, aviation, directors and officers liability,
financial institutions, construction, energy, media and entertainment. In 1999,
significant investments were made in professional talent, technology and the
development of specialized products and services to meet the evolving needs of
clients.

Subsidiaries of Aon Risk Services Companies and Aon Holdings operate
through owned offices in North America and Europe, as well as in South America,
Africa, Australia and Asia. The acquisition of A&A significantly augmented the
Registrant's presence in Latin America, Asia, Africa and Australia, and the
acquisitions of Jauch &

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Hubener, Le Blanc de Nicolay, Gil y Carvajal and The Nikols Group strengthened
the Registrant's presence throughout Europe.

Aon Services Group addresses the highly specialized product development,
consulting and administrative risk management needs of professional groups,
service businesses, governments, healthcare providers and commercial
organizations. It also provides underwriting management skills, claims and risk
management expertise, and third-party administration services to insurance
companies. Aon Services Group operating subsidiaries market and broker both the
primary and reinsurance risks of these programs. For individuals and businesses,
Aon Services Group provides affinity products for professional liability, life,
disability income and personal lines. The acquisition of The Minet Group by the
Registrant augmented Aon Services Group's already strong expertise in wholesale
brokerage and professional liability programs. The 1998 acquisition of Auto
Insurance Specialists, Inc., an insurance broker specializing in automobile
insurance coverages, gives Aon Services Group a significant presence in that
market with opportunities for wide geographic application.

Aon's reinsurance brokerage activities are organized under Aon Re in the
United States and AGL in the United Kingdom. Aon Re is the largest reinsurance
broker in the world, offering reinsurance, analytical services and alternative
risk financing vehicles. Aon Re serves the alternative market with reinsurance
placement, alternative risk services, captive management services and
catastrophe information forecasting. AGL is a London-based Lloyd's broker that
places wholesale and reinsurance business in the London and international
markets and serves the needs of a wide range of clients around the world.

AMO was established by Aon in late 1997 and is a leader in specialty
underwriting solutions and custom-designed products and services. Several of
AMO's specialties include entertainment, public entities, professional
liability, workers compensation, and media business and financial institutions.


(2) CONSULTING

Aon Consulting Worldwide, Inc. ("Aon Consulting")

Subsidiaries of Aon Consulting (and the European benefits operations of
Aon Holdings) serve the employee benefit needs of clients around the world. Aon
Consulting is one of the world's largest integrated human resources consulting
organizations. Focusing on the increasing demand for outsourcing solutions, Aon
Consulting targets emerging businesses, IPOs, recent mergers and acquisitions
and corporations that are reengineering staff functions.

In the United States, the benefits environment continues to change as
companies look for ways to manage their benefits costs while increasing the
choices offered to their employees. Aon Consulting, with its expertise in all
areas of benefits and compensation, and its access to the Registrant's other
subsidiaries, is well-positioned to serve this market. Aon Consulting
subsidiaries offer services to clients including organizational analysis and HR
strategic planning, recruitment and selection, benefits design and management
training and development, job design and competency modeling; compensation and
reward systems; human resources compliance and risk management; and individual
and organizational change management. Benefits issues in foreign countries are
becoming more complicated, and Aon Holdings and Aon Consulting anticipate
increased demand for their services in these markets.


- 3 -

(3) INSURANCE UNDERWRITING

Combined Insurance Company of America ("Combined Insurance"); Combined
Life Insurance Company of New York ("CLICNY"); Virginia Surety Company, Inc.
("VSC"); London General Insurance Company Limited ("London General"); and Aon
Warranty Group, Inc. ("Aon Warranty").

The Registrant's insurance underwriting subsidiaries are part of a highly
competitive industry that serves individual consumers in North America, Europe,
Latin America and the Pacific by providing accident and health coverage,
traditional life insurance and extended warranties through distribution networks
most of which are directly owned by the Registrant's subsidiaries.

The life and accident and health distribution network encompasses
primarily the agents of Combined Insurance and CLICNY ( which operates
exclusively in the State of New York). With more than five million policy-
holders, Combined Insurance has more individual accident policies in force
than any other United States company. Combined Insurance, the Registrant's
principal life and accident and health insurer, has a direct sales force of
several thousand career agents calling on individuals to sell a broad spectrum
of accident and health products and is one of the few companies with agents that
call on customers every six months to renew coverage and to sell additional
coverage. Combined Insurance's current product portfolio often allows policy-
holders the option of paying premiums monthly through a pre-authorized check
mechanism. Those policyholders are still called on by an agent to add additional
coverage. Combined Insurance offers a wide range of accident-only and sickness-
only insurance products, including short-term disability, cancer aid, Medicare
supplement, disability income and long-term care coverage. Most of Combined
Insurance's products are primarily fixed indemnity obligations, thereby not
subject to escalating medical costs. Combined Insurance offers a simplified
accident and sickness long-term disability policy. In addition to its
traditional business, Combined Insurance has expanded its product distribution
through payroll deduction, worksite marketing programs. Combined Insurance's
business is conducted by the Registrant's operations in the United States,
Canada, Latin America, Europe and Asia Pacific. Combined Insurance and CLICNY
market whole life products through direct sales career agents in the United
States.

The Registrant's extended warranty and specialty insurance business,
conducted by VSC subsidiaries in North America, South America and Asia Pacific
and London General in Europe, is composed primarily of extended warranty
insurance products, professional liability insurance coverages, workers'
compensation and specialty financial institution coverages. VSC and London
General are among the world's largest underwriters of consumer extended
warranties. The automobile warranty products are sold in the United States,
Canada, the United Kingdom, Ireland, France, The Netherlands, Belgium, Spain,
Argentina, Brazil, Australia and Japan. Aon Warranty Group handles the
administration of certain extended warranty products on automobiles, electronic
goods, personal computers and appliances. It serves manufacturers, distributors
and retailers of major worldwide consumer product and financial institutions,
associations and affinity groups in North America and in Europe.


- 4 -

(4) DISCONTINUED OPERATIONS

The Registrant hereby incorporates by reference note 4 of the Notes to
Consolidated Financial Statements on page 35 of the Annual Report.


LICENSING AND REGULATION

Regulatory authorities in the states or countries in which the operating
subsidiaries of Aon Group conduct business may require individual or company
licensing to act as brokers, agents, third party administrators, managing
general agents, reinsurance intermediaries or adjusters. Under the laws of most
states in the United States and in most foreign countries, regulatory
authorities have relatively broad discretion with respect to granting, renewing
and revoking brokers' and agents' licenses to transact business in the state or
country. The manner of operating in particular states and countries may vary
according to the licensing requirements of the particular state or country,
which may require, among other things, that a firm operate in the state or
country through a local corporation. In a few states and countries, licenses are
issued only to individual residents or locally-owned business entities. In such
cases, Aon Group subsidiaries have arrangements with residents or business
entities licensed to act in the state or country.

Insurance companies must comply with laws and regulations of the
jurisdictions in which they do business. These laws and regulations are designed
to ensure financial solvency of insurance companies and to require fair and
adequate service and treatment for policyholders. They are enforced by the
states in the United States, by industry self-regulating agencies in the United
Kingdom, and by various regulatory agencies in other countries through the
granting and revoking of licenses to do business, licensing of agents,
monitoring of trade practices, policy form approval, minimum loss ratio
requirements, limits on premium and commission rates, and minimum reserve and
capital requirements. Compliance is monitored by the state insurance departments
through periodic regulatory reporting procedures and periodic examinations. The
quarterly and annual financial reports to the regulators in the United States
utilize statutory accounting principles which are different from the generally
accepted accounting principles used in stockholders' reports. The statutory
accounting principles, in keeping with the intent to assure the protection of
policyholders are based, in general, on a liquidation concept while generally
accepted accounting principles are based on a going-concern concept.

The state insurance regulators are members of the National Association of
Insurance Commissioners ("NAIC"). This Association seeks to promote uniformity
of, and to enhance the state regulation of, insurance. Both the NAIC and the
individual states continue to focus on the solvency of insurance companies and
their conduct in the market place. This focus is reflected in additional
regulatory oversight by the states and emphasis on the enactment or adoption of
a series of NAIC model laws and regulations designed to promote solvency. Any
increase in any solvency-related oversight by the states is not expected to have
any significant impact on the insurance business of the Registrant.

Several years ago, the NAIC developed a formula for analyzing insurers
called risk-based capital ("RBC"). RBC is intended to establish "minimum"
capital threshold levels that vary with the size and mix of a company's
business. It is designed to identify companies with the capital levels that may
require regulatory attention. RBC does not have any significant impact on the
insurance business of the Registrant.

The state insurance holding company laws require prior notice to and
approval of the domestic state insurance department of intracorporate transfers
of assets within the holding company structure, including the payment of
dividends by insurance company subsidiaries. In addition, the premium finance
loans by Cananwill, Inc., an indirect wholly-owned subsidiary of the Registrant,
are subject to one or more of truth-in-lending and credit regulations, insurance
premium finance acts, retail installment sales acts and other similar consumer
protection legislation. Failure to comply with such laws or regulations can
result in the temporary suspension or permanent loss of the right to engage in
business in a particular jurisdiction as well as other penalties.

Recent federal and state laws and proposals mandating specific practices
by medical insurers and the health care industry will not, because of the nature
of the business of the Registrant's subsidiaries, materially affect the
Registrant. Numerous states have had legislation introduced to reform the health
care system and such legislation has passed in several states. While it is
impossible to forecast the precise nature of future federal and state health
care changes, the Registrant does not expect a major impact on its operations
because of the supplemental nature of

- 5 -


most of the policies issued by its insurance subsidiaries and because the
coverages are primarily purchased to provide, on a fixed-indemnity basis,
protection against loss-of-time or disability benefits. Congress has passed the
Financial Services Modernization Act commonly known as S 900 or the Gramm,
Leach, Bliley Act. While S 900 makes substantial changes in allowing financial
organizations to diversify, the Registrant does not believe the enactment of
S 900 will have a material effect on the business of its insurance institutions.


CLIENTELE

No significant part of the Registrant's or its subsidiaries' business is
dependent upon a single client or on a few clients, the loss of any one of which
would have a material adverse effect on the Registrant.


EMPLOYEES

The Registrant's subsidiaries had approximately 50,000 employees at the
end of 1999 of whom approximately 42,000 are salaried and hourly employees and
the remaining 8,000 are sales representatives who are generally compensated
wholly or primarily by commission.


ITEM 2. PROPERTIES.

The Registrant's subsidiaries own and occupy office buildings in six
states and certain foreign countries, and lease office space elsewhere in the
United States and in various foreign cities. Loss of the use of any owned or
leased property, while potentially disruptive, would have no material impact on
the Registrant.


- 6 -

ITEM 3. LEGAL PROCEEDINGS.

The Registrant hereby incorporates by reference note 13 of the Notes to
Consolidated Financial Statements on pages 47 and 48 of the Annual Report.

ITEM 4. SUBMISSION OF MATTERS TO A VOTE OF SECURITY HOLDERS.

None.

EXECUTIVE OFFICERS OF THE REGISTRANT

Executive officers of the Registrant are regularly elected by its Board of
Directors at the annual meeting of the Board which is held following each annual
meeting of the stockholders of the Registrant. The executive officers of the
Registrant were elected to their current positions on April 16, 1999 to serve
until the meeting of the Board following the annual meeting of stockholders on
April 18, 2000. Ages shown are as of December 31, 1999.

For information concerning certain directors and executive officers of the
Registrant, see item 10 below. As of March 24, 2000, the following individuals
are also executive officers of the Registrant as defined in Rule 16a-1(f):

HAS
CONTINUOUSLY
SERVED AS AN
OFFICER
OF REGISTRANT OR
NAME, AGE, AND ONE OR MORE OF
CURRENT OFFICE ITS SUBSIDIARIES BUSINESS EXPERIENCE
OR PRINCIPAL POSITION SINCE PAST 5 YEARS
--------------------- ----- ------------

Harvey N. Medvin, 63 1972 Mr. Medvin became Vice President
Executive Vice President and and Chief Financial Officer of the
Chief Financial Officer Registrant in 1982 and was elected to
his current position in 1987. He
also serves as a Director or Officer
of certain of the Registrant's
subsidiaries.

Daniel T. Cox, 53 1986 Mr. Cox was elected to his current
Executive Vice President position in 1991 and, prior to their
sale in 1996, had served as Chairman
and Chief Executive Officer of
certain of the Registrant's under-
writing subsidiaries. Mr. Cox has
headed the Registrant's benefits
consulting operation since 1987. He
also serves as Director or Officer
of certain of the Registrant's
subsidiaries.

Michael A. Conway, 52 1990 Mr. Conway was Vice President of
Senior Vice President and Combined Insurance from 1980 to
Senior Investment Officer 1984. Following other employment,
Mr. Conway rejoined the Registrant
in 1990 as Senior Vice President of
Combined Insurance and was elected
to his current position in 1991. He
also serves as Director or Officer
of certain of the Registrant's
subsidiaries.


- 7 -

PART II


ITEM 5. MARKET FOR THE REGISTRANT'S COMMON STOCK AND RELATED SECURITY HOLDER
MATTERS.

The Registrant's $1.00 par value common shares ("Common Shares") are
traded on the New York, Chicago and London stock exchanges. The Registrant
hereby incorporates by reference the "Dividends paid per share" and "Price
range" data on page 52 of the Annual Report.

The Registrant had approximately 13,300 holders of record of its Common
Shares as of February 23, 2000.

The Registrant hereby incorporates by reference note 9 of the Notes to
Consolidated Financial Statements on page 40 of the Annual Report.


ITEM 6. SELECTED FINANCIAL DATA.

The Registrant hereby incorporates by reference the "Selected Financial
Data" table on page 52 of the Annual Report.


ITEM 7. MANAGEMENT'S DISCUSSION AND ANALYSIS OF FINANCIAL CONDITION AND
RESULTS OF OPERATIONS.

The Registrant hereby incorporates by reference "Financial and Operations
Highlights - Management's Discussion and Analysis" on pages 18 through 24 and
"Information Concerning Forward-Looking Statements" on page 54 of the Annual
Report.


ITEM 7A. QUANTITATIVE AND QUALITATIVE DISCLOSURES ABOUT MARKET RISK.

The Registrant hereby incorporates by reference "Market Risk Exposure" on
pages 23 and 24 of the Annual Report.

ITEM 8. FINANCIAL STATEMENTS AND SUPPLEMENTARY DATA.

The Registrant hereby incorporates by reference the following statements,
notes and data from the Annual Report.
Page(s)
-------
Consolidated Financial Statements ..................... 25 - 29
Notes to Consolidated Financial Statements ............ 30 - 50
Report of Ernst & Young LLP, Independent Auditors ..... 51
Quarterly Financial Data .............................. 53


ITEM 9. CHANGES IN AND DISAGREEMENT WITH ACCOUNTANTS ON ACCOUNTING AND
FINANCIAL DISCLOSURE.

Not Applicable.


- 8 -

PART III


ITEM 10. DIRECTORS AND EXECUTIVE OFFICERS OF THE REGISTRANT.

The Registrant hereby incorporates by reference the information on pages
3, 6 and 7 of the Proxy Statement For The Annual Meeting of the Stockholders on
April 18, 2000, of the Registrant ("Proxy Statement") concerning the following
Directors of the Registrant, each of whom also serves as an executive officer of
the Registrant as defined in Rule 16a-1(f): Patrick G. Ryan, Michael D.
O'Halleran and Raymond I. Skilling. Information concerning additional executive
officers of the Registrant is contained in Part I hereof, pursuant to General
Instruction G(3) and Instruction 3 to Item 401(b) of Regulation S-K. The
Registrant also hereby incorporates by reference the information on pages 10
through 12 of the Proxy Statement.


ITEM 11. EXECUTIVE COMPENSATION.

The Registrant hereby incorporates by reference the information under the
headings "Executive Compensation," "Aggregated Option Exercises in Last Fiscal
Year and Fiscal Year-End Option Values," "Option Grants in 1999 Fiscal Year" and
"Pension Plan Table" on pages 14 through 17 of the Proxy Statement.


ITEM 12. SECURITY OWNERSHIP OF CERTAIN BENEFICIAL OWNERS AND MANAGEMENT.

The Registrant hereby incorporates by reference the share ownership data
contained on pages 2, 9 and 10 of the Proxy Statement.


ITEM 13. CERTAIN RELATIONSHIPS AND RELATED TRANSACTIONS.

The Registrant hereby incorporates by reference the information under the
heading "Transactions With Management" on page 21 of the Proxy Statement.


- 9 -

PART IV


ITEM 14. EXHIBITS, FINANCIAL STATEMENT SCHEDULES AND REPORTS ON FORM 8-K.

(a) (1) and (2). The Registrant has incorporated by reference from the Annual
Report (see Item 8) the following consolidated financial statements of the
Registrant and subsidiaries:



Annual
Report
Page(s)
-------


Consolidated Statements of Income - Years Ended December 31, 1999, 1998 and 1997 25

Consolidated Statements of Financial Position - As of December 31, 1999 and 1998 26-27

Consolidated Statements of Stockholders' Equity - Years Ended December 31, 1999,
1998 and 1997 28

Consolidated Statements of Cash Flows - Years Ended December 31, 1999, 1998 and
1997 29

Notes to Consolidated Financial Statements 30-50

Report of Ernst & Young LLP, Independent Auditors 51


Financial statement schedules of the Registrant and consolidated subsidiaries
not included in the Annual Report but filed herewith:
Consolidated Financial Statement Schedules -

Schedule
--------
Condensed Financial Information of Registrant I
Valuation and Qualifying Accounts II


All other schedules for Aon Corporation and Subsidiaries have been omitted
because the required information is not present in amounts sufficient to require
submission of the schedules or because the information required is included in
the respective financial statements or notes thereto. The following
supplementary schedules have been provided for Aon Corporation and Subsidiaries
as they relate to the insurance underwriting operations:

Schedule
--------
Summary of Investments Other than Investments in Related Parties II.1
Reinsurance II.2
Supplementary Insurance Information II.3


(A)(3). EXHIBITS

(a) Second Restated Certificate of Incorporation of the Registrant -
incorporated by reference to Exhibit 3(a) to the Registrant's Annual
Report to the Securities and Exchange Commission on Form 10-K for
the year ended December 31, 1991 (the "1991 Form 10-K").

(b) Certificate of Amendment of the Registrant's Second Restated
Certificate of Incorporation - incorporated by reference to Exhibit
3 to the Registrant's Quarterly Report on Form 10-Q for the quarter
ended March 31, 1994 (the "First Quarter 1994 Form 10Q").

(c) Bylaws of the Registrant - incorporated by reference to Exhibit (d)
to the Registrant's Annual Report to the Securities and Exchange
Commission on Form 10-K for the year ended December 31, 1982 (the
"1982 Form 10-K").

- 10 -

(d) Indenture dated September 15, 1992 between the Registrant and
Continental Bank Corporation (now known as Bank of America
Illinois), as Trustee - incorporated by reference to Exhibit 4(a) to
the Registrant's Current Report on Form 8-K dated September 23,
1992.

(e) Resolutions establishing terms of 6.875% Notes Due 1999 and 7.40%
Notes Due 2002 - incorporated by reference to Exhibits 4(d) to the
Registrant's Annual Report to the Securities and Exchange Commission
on Form 10-K for the year ended December 31, 1992 (the "1992 Form
10-K").

(f) Resolutions establishing the terms of 6.70% Notes Due 2003 and 6.30%
Notes Due 2004 incorporated by reference to Exhibits 4(c) and 4(d)
of the Registrant's Annual Report to the Securities and Exchange
Commission on Form 10-K for the year ended December 31, 1993 (the
"1993 Form 10-K").

(g) Resolutions establishing the terms of the 6.90 % Notes Due 2004.

(h) Junior Subordinated Indenture dated as of January 13, 1997 between
the Registrant and The Bank of New York, as trustee - incorporated
by reference to Exhibit 4.1 of the Registrant's Amendment No. 1 to
Registration Statement on Form S-4 No. 333-21237 dated March 27,
1997 (the "Capital Securities Registration").

(i) First Supplemental Indenture dated as of January 13, 1997 between
the Registrant and the Bank of New York, as trustee - incorporated
by reference to Exhibit 4.2 of the Capital Securities Registration.

(j) Certificate of Trust of Aon Capital A - incorporated by reference to
Exhibit 4.3 of the Capital Securities Registration.

(k) Amended and Restated Trust Agreement of Aon Capital A dated as of
January 13, 1997 among the Registrant, as Depositor, The Bank of New
York, as Property Trustee, The Bank of New York (Delaware), as
Delaware Trustee, the Administrative Trustees named therein and the
holders, from time to time, of the Capital Securities - incorporated
by reference to Exhibit 4.5 of the Capital Securities Registration.

(l) Capital Securities Guarantee Agreement dated as of January 13, 1997
between the Registrant and the Bank of New York, as guarantee
trustee - incorporated by reference to Exhibit 4.8 of the Capital
Securities Registration.

(m) Capital Securities Exchange and Registration Rights Agreement dated
as of January 13, 1997 among the Registrant, Aon Capital A and
Morgan Stanley & Co. Incorporated and Goldman, Sachs & Co. -
incorporated by reference to Exhibit 4.10 of the Capital Securities
Registration.

(n) Debenture Exchange and Registration Rights Agreement dated as of
January 13, 1997 among the Registrant, Aon Capital A and Morgan
Stanley & Co. Incorporated and Goldman, Sachs & Co. - incorporated
by reference to Exhibit 4.11 of the Capital Securities Registration.

(o) Guarantee Exchange and Registration Rights Agreement dated as of
January 13, 1997 among the Registrant, Aon Capital A and Morgan
Stanley & Co. Incorporated and Goldman, Sachs & Co. - incorporated
by reference to Exhibit 4.12 of the Capital Securities Registration.

(p) Certificate of Designation for the Registrant's Series C Cumulative
Preferred Stock - incorporated by reference to Exhibit 4.1 to the
Registrant's Current Report on Form 8-K dated February 9, 1994.

(q) Registration Rights Agreement dated November 2, 1992 by and between
the Registrant and Frank B. Hall & Co., Inc. - incorporated by
reference to Exhibit 4(c) to the Third Quarter 1992 Form 10-Q.

- 11 -

(r) Registration rights agreement by and among the Registrant and
certain affiliates of Ryan Insurance Group, Inc. (including Patrick
G. Ryan and Andrew J. McKenna) - incorporated by reference to
Exhibit (f) to the 1982 Form 10-K.

(s) Aon Corporation Outside Director Deferred Compensation Agreement by
and among the Registrant and Registrant's directors who are not
salaried employees of Registrant or Registrant's affiliates.

(t) Amendment and Waiver Agreement dated as of November 4, 1991 among
the Registrant and each of Patrick G. Ryan, Shirley Ryan, Ryan
Enterprises Corporation and Harvey N. Medvin - incorporated by
reference to Exhibit 10(j) to the 1991 Form 10-K.

(u) Statement regarding Computation of Ratio of Earnings to Fixed
Charges.

(v) Statement regarding Computation of Ratio of Earnings to Combined
Fixed Charges and Preferred Stock Dividends.

(w) Aon Corporation 1994 Amended and Restated Outside Director Stock
Award Plan - incorporated by reference to Exhibit 10(b) to the First
Quarter 1994 Form 10-Q.

(x) Annual Report to Stockholders of the Registrant for the year ended
December 31, 1999 (for information, and not to be deemed filed,
except for those portions specifically incorporated by reference
herein).

(y) List of Subsidiaries of the Registrant.

(z) Consent of Ernst & Young LLP to the incorporation by reference into
Aon's Annual Report on Form 10-K of its report included in the 1999
Annual Report to Stockholders and into Aon's Registration Statement
Nos. 33-27984, 33-42575, 33-59037, 333-21237, 333-50607, 333-55773
and 333-78723.

(aa) Annual Report to the Securities and Exchange Commission on Form 11-K
for the Aon Savings Plan for the year ended December 31, 1999 - to
be filed by amendment as provided in Rule 15d- 21(b).

(ab) Executive Compensation Plans and Arrangements:

(A) Aon Stock Option Plan (as amended and restated through 1997) -
incorporated by reference to Exhibit 10 (a) to the
Registrant's Quarterly Report to the Securities and Exchange
Commission on Form 10-Q for the Quarter ended March 31, 1997
(the "First Quarter 1997 Form 10-Q").

(B) First Amendment to the Aon Stock Option Plan as Amended and
Restated Through 1997- incorporated by reference to Exhibit
10(a) to the Registrant's Quarterly Report to the Securities
and Exchange Commission on Form 10-Q for the quarter ended
March 31, 1999 (the "First Quarter 1999 Form 10-Q").

(C) Aon Stock Award Plan (as amended and restated through 1997) -
incorporated by reference to Exhibit 10(b) to the First
Quarter 1997 Form 10-Q.

(D) First Amendment to the Aon Stock Award Plan as Amended and
Restated Through 1997- incorporated by reference to Exhibit
10(b) to the First Quarter 1999 Form 10-Q.


- 12 -

(E) Aon Corporation 1995 Senior Officer Incentive Compensation
Plan incorporated by reference to Exhibit 10(p) to the
Registrant's Annual Report to the Securities and Exchange
Commission on Form 10-K for the year ended December 31, 1995
(the "1995 Form 10-K").

(F) Aon Deferred Compensation Plan and First Amendment to the Aon
Deferred Compensation Plan - incorporated by reference to
Exhibit 10(q) of the 1995 Form 10-K.

(G) 1999 Aon Deferred Compensation Plan.

(H) Employment Agreement dated June 1, 1993 by and among the
Registrant, Aon Risk Services, Inc. and Michael D. O'Halleran,
incorporated by reference to Exhibit 10(p) to the Registrant's
Annual Report to the Securities and Exchange Commission on
Form 10-K for the year ended December 31, 1998.

(I) Aon Severance Plan - incorporated by reference to Exhibit 10
to the Registrant's Quarterly Report to the Securities and
Exchange Commission and Form 10-Q for the quarter ended June
30, 1997.

(ac) Asset Purchase Agreement dated July 24, 1992 between the Registrant
and Frank B. Hall & Co. Inc. - incorporated by reference to Exhibit
10(c) to the Registrant's Quarterly Report on Form 10- Q for the
period ended June 30, 1992.

(ad) Stock Purchase Agreement by and among the Registrant, Combined
Insurance Company of America, Union Fidelity Life Insurance Company
and General Electric Capital Corporation dated as of November 11,
1995 - incorporated by reference to Exhibit 10(s) of the 1995 Form
10-K.

(ae) Stock Purchase Agreement by and among the Registrant; Combined
Insurance Company of America; The Life Insurance Company of
Virginia; Forth Financial Resources, Ltd.; Newco Properties, Inc.;
and General Electric Capital Corporation dated as of December 22,
1995 - incorporated by reference to Exhibit 10(t) of the 1995 Form
10-K.

(af) Agreement and Plan of Merger among the Registrant; Subsidiary
Corporation, Inc. ("Purchaser"); and Alexander & Alexander Services
Inc. ("A&A") dated as of December 11, 1996 - incorporated by
reference to Exhibit (c)(1) of the Registrant's Tender Offer
Statement on Schedule 14D-1 filed by the Registrant with the
Securities and Exchange Commission ("SEC") on December 16, 1996 (the
"Schedule 14D-1").

(ag) First Amendment to Agreement and Plan of Merger, dated as of January
7, 1997, among the Registrant, Purchaser and A&A - incorporated by
reference to Exhibit (c)(3) to the Schedule 14D-1 filed by the
Registrant with the SEC on January 9, 1997.

(b) Reports on Form 8-K.

The Registrant filed no Current Reports on Form 8-K during the last
quarter of the Registrant's year ended December 31, 1999.


- 13 -

SIGNATURES


Pursuant to the requirements of Section 13 or 15(d) of the Securities
Exchange Act of 1934, the Registrant has duly caused this report to be signed on
its behalf by the undersigned, thereunto duly authorized, on the 17th day of
March, 2000.

Aon Corporation



By: /s/ PATRICK G. RYAN
-------------------
Patrick G. Ryan, Chairman
and Chief Executive Officer


Pursuant to the requirements of the Securities Exchange Act of 1934, this
Report has been signed below by the following persons on behalf of the
Registrant and in the capacities and on the dates indicated.

SIGNATURE TITLE DATE
--------- ----- ----


/s/ PATRICK G. RYAN Chairman, Chief Executive March 17, 2000
- - - - - - - - - - - - - - - - - ---------------------------- Officer and Director
Patrick G. Ryan (Principal Executive Officer)


/s/DANIEL T. CARROLL Director March 17, 2000
- - - - - - - - - - - - - - - - - ----------------------------
Daniel T. Carroll


/s/FRANKLIN A. COLE Director March 17, 2000
- - - - - - - - - - - - - - - - - ----------------------------
Franklin A. Cole


/s/EDGAR D. JANNOTTA Director March 17, 2000
- - - - - - - - - - - - - - - - - ----------------------------
Edgar D. Jannotta


/s/LESTER B. KNIGHT Director March 17, 2000
- - - - - - - - - - - - - - - - - ----------------------------
Lester B. Knight


/s/PERRY J. LEWIS Director March 17, 2000
- - - - - - - - - - - - - - - - - ----------------------------
Perry J. Lewis


/s/ANDREW J. McKENNA Director March 17, 2000
- - - - - - - - - - - - - - - - - ----------------------------
Andrew J. McKenna


/s/NEWTON N. MINOW Director March 17, 2000
- - - - - - - - - - - - - - - - - ----------------------------
Newton N. Minow



- 14 -


SIGNATURE TITLE DATE
--------- ----- ----


/s/RICHARD C. NOTEBAERT Director March 17, 2000
- - - - - - - - - - - - - - - - - ----------------------------
Richard C. Notebaert


/s/MICHAEL D. O'HALLERAN Director March 17, 2000
- - - - - - - - - - - - - - - - - ----------------------------
Michael D. O'Halleran



/s/DONALD S. PERKINS Director March 17, 2000
- - - - - - - - - - - - - - - - - ----------------------------
Donald S. Perkins


/s/JOHN W. ROGERS, JR. Director March 17, 2000
- - - - - - - - - - - - - - - - - ----------------------------
John W. Rogers, Jr.


/s/GEORGE A. SCHAEFER Director March 17, 2000
- - - - - - - - - - - - - - - - - ----------------------------
George A. Schaefer


/s/RAYMOND I. SKILLING Director March 17, 2000
- - - - - - - - - - - - - - - - - ----------------------------
Raymond I. Skilling


/s/FRED L. TURNER Director March 17, 2000
- - - - - - - - - - - - - - - - - ----------------------------
Fred L. Turner


/s/ARNOLD R. WEBER Director March 17, 2000
- - - - - - - - - - - - - - - - - ----------------------------
Arnold R. Weber


/s/CAROLYN Y. WOO Director March 17, 2000
- - - - - - - - - - - - - - - - - ----------------------------
Carolyn Y. Woo


/s/HARVEY N. MEDVIN Executive Vice President March 17, 2000
- - - - - - - - - - - - - - - - - ---------------------------- and Chief Financial
Harvey N. Medvin Officer
(Principal Financial and
Accounting Officer)


- 15 -



SCHEDULE I

Aon Corporation
(Parent Company)
CONDENSED STATEMENTS OF FINANCIAL POSITION


As of December 31
------------------------
(millions) 1999 1998
----------- -----------

ASSETS

Investments in subsidiaries ........................ $ 5,585 $ 5,305
Notes receivable - subsidiaries .................... 447 239
Cash and cash equivalents .......................... 17 6
Other assets ....................................... 123 84
----------- -----------
Total Assets ................................... $ 6,172 $ 5,634
=========== ===========

LIABILITIES AND STOCKHOLDERS' EQUITY
LIABILITIES
Short-term borrowings .............................. $ 823 $ 436
6.3% long-term debt securities ..................... 100 100
7.4% long-term debt securities ..................... 100 100
6.875% long-term debt securities.................... - 100
6.9% long-term debt securities ..................... 250 -
6.7% long-term debt securities ..................... 150 150
Subordinated debt .................................. 800 800
Notes payable - subsidiaries ....................... 622 588
Notes payable - other .............................. 70 70
Debt guarantee of employee stock ownership plan .... - 17
Accrued expenses and other liabilities ............. 156 206
----------- -----------
TOTAL LIABILITIES .............................. 3,071 2,567
----------- -----------

Redeemable Preferred Stock ........................ 50 50

STOCKHOLDERS' EQUITY
Common stock ....................................... 259 172
Paid-in additional capital ......................... 525 450
Accumulated other comprehensive loss ............... (309) (116)
Retained earnings .................................. 2,905 2,782
Less treasury stock at cost ........................ (90) (58)
Less deferred compensation ......................... (239) (213)
----------- -----------
TOTAL STOCKHOLDERS' EQUITY ..................... 3,051 3,017
----------- -----------
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY ..... $ 6,172 $ 5,634
=========== ===========
See notes to condensed financial statements.


- 16 -



SCHEDULE I
(Continued)

Aon Corporation
(Parent Company)
CONDENSED STATEMENTS OF INCOME


Years Ended December 31
----------------------------
(millions) 1999 1998 1997
-------- -------- --------

REVENUE

Dividends from subsidiaries ........................ $ 467 $ 351 $ 180
Other investment income ............................ 20 69 51
-------- -------- --------
TOTAL REVENUE ................................. 487 420 231
-------- -------- --------


EXPENSES
Operating and administrative ....................... 13 20 6
Interest - subsidiaries ............................ 96 94 85
Interest - other ................................... 85 76 62
-------- -------- --------
TOTAL EXPENSES ................................ 194 190 153
-------- -------- --------


INCOME BEFORE INCOME TAXES AND EQUITY (DEFICIT) IN
UNDISTRIBUTED INCOME OF SUBSIDIARIES ................ 293 230 78
Income tax benefit ................................. 70 54 43
-------- -------- --------
363 284 121
EQUITY (DEFICIT) IN UNDISTRIBUTED INCOME OF SUBSIDIARIES.. (11) 257 178
-------- -------- --------
NET INCOME ......................................... $ 352 $ 541 $ 299
======== ======== ========
- - - - - - - - - - - - - - - - - -------------------------------------------------------------------------------------------
See notes to condensed financial statements.



- 17 -



SCHEDULE I
(Continued)

Aon Corporation
(Parent Company)
CONDENSED STATEMENTS OF CASH FLOWS


Years Ended December 31
------------------------------
(millions) 1999 1998 1997
-------- --------- ---------



CASH FLOWS FROM OPERATING ACTIVITIES ............................ $ 287 $ 445 $ 124

CASH FLOWS FROM INVESTING ACTIVITIES:
Investments in subsidiaries ............................... (363) (93) (1,355)
Notes receivables from subsidiaries ....................... (208) (16) (135)
-------- --------- ---------
CASH USED BY INVESTING ACTIVITIES .................... (571) (109) (1,490)
-------- --------- ---------

CASH FLOWS FROM FINANCING ACTIVITIES:
Treasury stock transactions - net ......................... (66) (18) 21
Issuance (repayment) of short-term borrowings - net ....... 387 (328) 542
Issuance of company-obligated mandatorily redeemable
preferred capital securities of subsidiary trust .. - - 800
Issuance of notes payable and long-term debt .............. 284 200 114
Repayment of long-term debt ............................... (100) - -
Retirement of preferred stock ............................. - - (136)
Cash dividends to stockholders ............................ (210) (194) (182)
-------- --------- ---------
CASH PROVIDED (USED) BY FINANCING ACTIVITIES ......... 295 (340) 1,159
-------- --------- ---------


INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS ................ 11 (4) (207)
CASH AND CASH EQUIVALENTS AT BEGINNING OF YEAR .................. 6 10 217
-------- --------- ---------
CASH AND CASH EQUIVALENTS AT END OF YEAR ........................ $ 17 $ 6 $ 10
======== ========= =========
See notes to condensed financial statements.



- 18 -

SCHEDULE I
(Continued)

Aon Corporation
(Parent Company)
NOTES TO CONDENSED FINANCIAL STATEMENTS


(1) See notes to consolidated financial statements incorporated by reference
from the Annual Report.

(2) Generally, the net assets of Aon's insurance subsidiaries available for
transfer to the parent company are limited to the amounts that the
insurance subsidiaries' statutory net assets exceed minimum statutory
capital requirements; however, payments of the amounts as dividends in
excess of $170 million may be subject to approval by regulatory
authorities.

(3) Subsidiary Guarantees
---------------------
In 1998, Aon guaranteed a committed bank credit facility under which
certain European subsidiaries can borrow up to EUR 400 million. At
December 31, 1999, loans of EUR 347 million ($351 million) were
outstanding under this facility.

An indirect wholly-owned subsidiary of Aon Corporation manages various
investment portfolios, totaling $297 million at December 31, 1999, held
in a collateral trust for the benefit of certain unaffiliated entities and
is obligated to produce specified investment returns for those portfolios.
Aon Corporation has unconditionally guaranteed the obligations of this
subsidiary.

(4) During 1998, Aon Corporation (Parent Company) reclassified $523 million of
notes receivables-subsidiaries to investments in subsidiaries related to
its brokerage operations.


- 19 -



SCHEDULE II
Aon CORPORATION and SUBSIDIARIES
VALUATION AND QUALIFYING ACCOUNTS
Years Ended December 31, 1999, 1998 and 1997


(MILLIONS) ADDITIONS
----------------------------
CHARGED/
BALANCE AT CHARGED TO (CREDITED) BALANCE
BEGINNING COST AND TO OTHER DEDUCTIONS AT END
DESCRIPTION OF YEAR EXPENSES ACCOUNTS (1) OF YEAR
- - - - - - - - - - - - - - - - - -------------------------------------------------------- ------------- ------------- ------------- -------------

YEAR ENDED DECEMBER 31, 1999
----------------------------
Reserve for losses (2)
(deducted from other long-term investments) $ 9 $ - $ (9) $ - $ -

Allowance for doubtful accounts (3)
(deducted from insurance brokerage
and consulting receivables) 93 12 (3) (14) 88

Allowance for doubtful accounts
(deducted from premiums and other) 6 1 - (1) 6


YEAR ENDED DECEMBER 31, 1998
----------------------------
Reserve for losses (2)
(deducted from other long-term investments) $ 9 $ - $ - $ - $ 9

Allowance for doubtful accounts (3)
(deducted from insurance brokerage
and consulting receivables) 81 20 (5) (3) 93

Allowance for doubtful accounts
(deducted from premiums and other) 5 1 - - 6


YEAR ENDED DECEMBER 31, 1997
----------------------------
Reserve for losses (2)
(deducted from other long-term investments) $ 5 $ - $ 4 $ - $ 9

Allowance for doubtful accounts (3)
(deducted from insurance brokerage
and consulting receivables) 60 9 27 (15) 81

Allowance for doubtful accounts
(deducted from premiums and other) 3 2 - - 5



(1) Amounts deemed to be uncollectible.
(2) Amounts shown in additions charged/(credited) to other accounts represent
(income) losses on disposals.
(3) Amounts shown in additions charged/(credited) to other accounts represent
reserves related to acquired business and foreign exchange.



- 20 -



SCHEDULE II.1
Aon Corporation and Subsidiaries
CONSOLIDATED SUMMARY OF INVESTMENTS -
OTHER THAN INVESTMENTS IN RELATED PARTIES
AS OF DECEMBER 31, 1999
Amount Shown
in Statement
Amortized Fair of Financial
(millions) Cost or Cost Value Position
------------ ------------ ------------


FIXED MATURITIES - AVAILABLE FOR SALE:
US government and agencies ................... $ 170 $ 160 $ 160
States and political subdivisions ............ 8 7 7
Debt securities of foreign governments
not classified as loans ................. 755 750 750
Corporate securities ......................... 1,530 1,450 1,450
Public utilities ............................. 47 45 45
Mortgage-backed securities ................... 44 43 43
Other fixed maturities ....................... 43 42 42
------------ ------------ ------------
TOTAL FIXED MATURITIES .................. 2,597 2,497 2,497
------------ ------------ ------------

EQUITY SECURITIES - AVAILABLE FOR SALE:
Common stocks:
Public utilities ......................... 2 1 1
Banks, trusts and insurance companies .... 151 149 149
Industrial, miscellaneous and all other .. 125 103 103
Non-redeemable preferred stocks .............. 384 321 321
------------ ------------ ------------
TOTAL EQUITY SECURITIES ................. 662 574 574
------------ ------------ ------------

Mortgage loans on real estate .................... 4 * 4 *
Real estate - net of depreciation ................ 10 * 10 *
Policy loans ..................................... 65 * 65 *
Other long-term investments ...................... 672 * 672 *
Short-term investments ........................... 2,362 2,362
------------ ------------
TOTAL INVESTMENTS ....................... $ 6,372 $ 6,184
------------ ------------


* These investment categories are combined and are shown as other
investments in the Statement of Financial Position.




- 21 -



SCHEDULE II.2

Aon Corporation and Subsidiaries
REINSURANCE


Y e a r E n d e d D e c e m b e r 3 1 , 1 9 9 9
--------------------------------------------------------------------------------------
Ceded to Assumed Percentage of
(millions) Gross other from other amount
amount companies companies Net amount assumed to net
--------------------------------------------------------------------------------------


LIFE INSURANCE IN FORCE ............ $ 14,444 $ 15,902 $ 7,567 $ 6,109 124%
=============== ================ ================ =============== ================

PREMIUMS
Life Insurance ................. $ 227 $ 93 $ 2 $ 136 2%
A&H Insurance .................. 1,167 257 91 1,001 9%
Specialty Property & Casualty .. 860 274 85 671 13%
--------------- ---------------- ---------------- --------------- ----------------
TOTAL PREMIUMS ............... $ 2,254 $ 624 $ 178 $ 1,808 10%
=============== ================ ================ =============== ================



Y e a r E n d e d D e c e m b e r 3 1 , 1 9 9 8
--------------------------------------------------------------------------------------
Ceded to Assumed Percentage of
Gross other from other amount
amount companies companies Net amount assumed to net
--------------------------------------------------------------------------------------

LIFE INSURANCE IN FORCE ............ $ 10,653 $ 9,813 $ 5,510 $ 6,350 87%
=============== ================ ================ =============== ================

PREMIUMS
Life Insurance ................. $ 235 $ 103 $ 7 $ 139 5%
A&H Insurance .................. 1,134 235 46 945 5%
Specialty Property & Casualty .. 734 241 96 589 16%
--------------- ---------------- ---------------- --------------- ----------------
TOTAL PREMIUMS ............... $ 2,103 $ 579 $ 149 $ 1,673 9%
=============== ================ ================ =============== ================



Y e a r E n d e d D e c e m b e r 3 1 , 1 9 9 7
--------------------------------------------------------------------------------------
Ceded to Assumed Percentage of
Gross other from other amount
amount companies companies Net amount assumed to net
--------------------------------------------------------------------------------------

LIFE INSURANCE IN FORCE ............ $ 10,438 $ 12,515 $ 8,823 $ 6,746 131%
=============== ================ ================ =============== ================

PREMIUMS
Life Insurance ................. $ 214 $ 154 $ 86 $ 146 59%
A&H Insurance .................. 1,073 278 140 935 15%
Specialty Property & Casualty .. 634 178 72 528 14%
--------------- ---------------- ---------------- --------------- ----------------
TOTAL PREMIUMS ............... $ 1,921 $ 610 $ 298 $ 1,609 19%
=============== ================ ================ =============== ================


- 22 -



SCHEDULE II.3
Aon Corporation and Subsidiaries
SUPPLEMENTARY INSURANCE INFORMATION

Future
policy
benefits Unearned
Deferred losses, premiums
policy claims and other Net
acquistion and loss policyholders' Premium investment
(millions) costs expenses funds revenue income(1)
----------- ------------ ----------- ------------ -----------

YEAR ENDED DECEMBER 31, 1999
- - - - - - - - - - - - - - - - - ----------------------------


Insurance brokerage and other services $ - $ - $ - $ - $ 159
Consulting - - - - 3
Insurance underwriting 636 1,769 3,219 1,808 251
Corporate and other - - - - 164
----------- ------------ ----------- ------------ -----------
TOTAL $ 636 $ 1,769 $ 3,219 $ 1,808 $ 577
=========== ============ =========== ============ ===========

YEAR ENDED DECEMBER 31, 1998
- - - - - - - - - - - - - - - - - ----------------------------

Insurance brokerage and other services $ - $ - $ - $ - $ 194
Consulting - - - - 6
Insurance underwriting 573 1,765 3,058 1,673 240
Corporate and other - - - - 150
----------- ------------ ----------- ------------ -----------
TOTAL $ 573 $ 1,765 $ 3,058 $ 1,673 $ 590
=========== ============ =========== ============ ===========


YEAR ENDED DECEMBER 31, 1997
- - - - - - - - - - - - - - - - - ----------------------------

Insurance brokerage and other services $ - $ - $ - $ - $ 163
Consulting - - - - 6
Insurance underwriting 549 1,752 2,698 1,609 214
Corporate and other - - - - 117
----------- ------------ ----------- ------------ -----------
TOTAL $ 549 $ 1,752 $ 2,698 $ 1,609 $ 500
=========== ============ =========== ============ ===========



Benefits Amortization
claims, of deferred
Commissions, losses and policy Other
fees settlement acquisition operating Premiums
(millions) and other expenses costs expenses written(2)
----------- ------------ ----------- ------------ -----------

YEAR ENDED DECEMBER 31, 1999
- - - - - - - - - - - - - - - - - ----------------------------

Insurance brokerage and other services $ 3,985 $ - $ - $ 3,651 $ -
Consulting 653 - - 698 -
Insurance underwriting 47 973 247 596 1,787
Corporate and other - - - 270 -
----------- ------------ ----------- ------------ -----------
TOTAL $ 4,685 $ 973 $ 247 $ 5,215 $ 1,787
=========== ============ =========== ============ ===========



YEAR ENDED DECEMBER 31, 1998
- - - - - - - - - - - - - - - - - ----------------------------

Insurance brokerage and other services $ 3,588 $ - $ - $ 3,119 $ -
Consulting 609 - - 547 -
Insurance underwriting 33 896 216 551 1,668
Corporate and other - - - 233 -
----------- ------------ ----------- ------------ -----------
TOTAL $ 4,230 $ 896 $ 216 $ 4,450 $ 1,668
=========== ============ =========== ============ ===========


YEAR ENDED DECEMBER 31, 1997
- - - - - - - - - - - - - - - - - ----------------------------

Insurance brokerage and other services $ 3,058 $ - $ - $ 2,917 $ -
Consulting 547 - - 508 -
Insurance underwriting 35 842 208 530 1,596
Corporate and other 2 - - 204 -
----------- ------------ ----------- ------------ -----------
TOTAL $ 3,642 $ 842 $ 208 $ 4,159 $ 1,596
=========== ============ =========== ============ ===========

(1) The above results reflect allocations of investment income and certain
expense elements considered reasonable under the circumstances. Results
include income (loss) on disposals of investments.
(2) Net of reinsurance ceded.



- 23 -

Cross Reference Sheet, Pursuant
to General Instruction G(4)


Item in Form 10-K Incorporated by Reference to
- - - - - - - - - - - - - - - - - ----------------- ----------------------------

PART I
- - - - - - - - - - - - - - - - - ------

Item 1. Business Annual Report to Stockholders of
the Registrant for the Year 1999
("Annual Report") pages 8 through
17, 19 through 21, and pages 35,
49 and 50.

Item 3. Legal Proceedings Annual Report pages 47 and 48 (note
13 of Notes to Consolidated
Financial Statements).

PART II
- - - - - - - - - - - - - - - - - -------

Item 5. Market for the Registrant's Annual Report page 40 (note 9 of
Common Stock and Related Notes to Consolidated Financial
Security Holder Matters Statements) and page 52 ("Dividends
paid per share" and "Price range").

Item 6. Selected Financial Data Annual Report page 52.

Item 7. Management's Discussion Annual Report pages 18 through
and Analysis of Financial 24 and page 54 ( "Information
Condition and Results of Concerning Forward-Looking
Operations Statements").


Item 7A. Quantitative and Qualitative Annual Report pages 23 and 24
Disclosures about Market Risk ("Market Risk Exposure").


Item 8. Financial Statements and Annual Report pages 25 through 50
Supplementary Data and 53.


PART III
- - - - - - - - - - - - - - - - - --------

Item 10. Directors and Executive Proxy Statement For Annual Meeting
Officers of the Registrant of Stockholders on April 18, 2000
of the Registrant ("Proxy
Statement") pages 3, 6, 7, and 10
through 12.

Item 11. Executive Compensation Proxy Statement pages 14 through
17.

Item 12. Security Ownership of Proxy Statement pages 2, 9 and 10.
Certain Beneficial Owners
and Management


Item 13. Certain Relationships and Proxy Statement page 21
Related Transactions ("Transactions With Management").


PART IV
- - - - - - - - - - - - - - - - - -------

Item 14. Exhibits, Financial Statement Annual Report pages 25 through 50.
Schedules, And Reports on
Form 8-K


- 24 -

EXHIBIT INDEX

EXHIBIT NUMBER PAGE NUMBER OF
REGULATION SEQUENTIALLY
S-K, ITEM 601 NUMBERED COPY
- - - - - - - - - - - - - - - - - ------------- -------------

(3) Articles of incorporation and bylaws:

(a) Second Restated Certificate of Incorporation of the Registrant -
incorporated by reference to Exhibit 3(a) to the 1991 Form 10-K.

(b) Certificate of Amendment of the Registrant's Second Restated
Certificate of Incorporation - incorporated by reference to Exhibit
3 to the First Quarter 1994 Form 10-Q.

(c) Bylaws of the Registrant - incorporated by reference to Exhibit (d)
to the 1982 Form 10-K.

(d) Certificate of Designation for the Registrant's Series C Cumulative
Preferred Stock - incorporated by reference to Exhibit 4.1 to the
Registrant's Current Report on Form 8-K dated February 9, 1994.

(4) Instruments defining the rights of security holders, including indentures:

(a) Indenture dated September 15, 1992 between the Registrant and
Continental Bank Corporation (now known as Bank of America
Illinois), as Trustee - incorporated by reference to Exhibit 4(a) of
the Registrant's Current Report on Form 8-K dated September 23,
1992.

(b) Resolutions establishing terms of 6.875% Notes Due 1999 and 7.40%
Notes Due 2002 - incorporated by reference to Exhibit 4(d) to the
1992 Form 10-K.

(c) Resolutions establishing the terms of 6.70% Notes Due 2003
incorporated by reference to Exhibit 4(c) to the 1993 Form 10-K.

(d) Resolutions establishing the terms of 6.30% Notes Due 2004
incorporated by reference to Exhibit 4(d) to the 1993 Form 10-K.

(e) Resolutions establishing the terms of 6.90% Notes due 2004.

(f) Junior Subordinated Indenture dated as of January 13, 1997 between
the Registrant and The Bank of New York, as trustee - incorporated
by reference to Exhibit 4.1 of the Registrant's Amendment No. 1 to
Registration Statement on Form S-4 No. 333-21237 dated March 27,
1997 (the "Capital Securities Registration").

(g) First Supplemental Indenture dated as of January 13, 1997 between
the Registrant and the Bank of New York, as trustee - incorporated
by reference to Exhibit 4.2 of the Capital Securities Registration.

(h) Certificate of Trust of Aon Capital A - incorporated by reference to
Exhibit 4.3 of the Capital Securities Registration.


- 25 -

EXHIBIT INDEX

EXHIBIT NUMBER PAGE NUMBER OF
REGULATION SEQUENTIALLY
S-K, ITEM 601 NUMBERED COPY
- - - - - - - - - - - - - - - - - ------------- -------------

(i) Amended and Restated Trust Agreement of Aon Capital A dated as of
January 13, 1997 among the Registrant, as Depositor, The Bank of New
York, as Property Trustee, The Bank of New York (Delaware), as
Delaware Trustee, the Administrative Trustees named therein and the
holders, from time to time, of the Capital Securities - incorporated
by reference to Exhibit 4.5 of the Capital Securities Registration.

(j) Capital Securities Guarantee Agreement dated as of January 13, 1997
between the Registrant and the Bank of New York, as guarantee
trustee - incorporated by reference to Exhibit 4.8 of the Capital
Securities Registration.

(k) Capital Securities Exchange and Registration Rights Agreement dated
as of January 13, 1997 among the Registrant, Aon Capital A and
Morgan Stanley & Co. Incorporated and Goldman, Sachs & Co. -
incorporated by reference to Exhibit 4.10 of the Capital Securities
Registration.

(l) Debenture Exchange and Registration Rights Agreement dated as of
January 13, 1997 among the Registrant, Aon Capital A and Morgan
Stanley & Co. Incorporated and Goldman, Sachs & Co. - incorporated
by reference to Exhibit 4.11 of the Capital Securities Registration.

(m) Guarantee Exchange and Registration Rights Agreement dated as of
January 13, 1997 among the Registrant, Aon Capital A and Morgan
Stanley & Co. Incorporated and Goldman, Sachs & Co. - incorporated
by reference to Exhibit 4.12 of the Capital Securities Registration.


(10) Material Contracts:

(a) Aon Stock Option Plan (as amended and restated through 1997) -
incorporated by reference to Exhibit 10(a) to the Registrant's
Quarterly Report to the Securities and Exchange Commission on Form
10-Q for the quarter ended March 31, 1997 (the "First Quarter 1997
Form 10-Q").

(b) First Amendment to the Aon Stock Option Plan as Amended and Restated
Through 1997 - incorporated by reference to Exhibit 10(a) to the
Registrant's Quarterly Report to the Securities and Exchange
Commission on Form 10-Q for the quarter ended March 31, 1999 (the
"First Quarter 1999 Form 10-Q").

(c) Registration Rights Agreement by and among the Registrant and
certain affiliates of Ryan Insurance Group, Inc. (Including Patrick
G. Ryan and Andrew J. McKenna) - incorporated by reference to
Exhibit (f) to the 1982 Form 10-K.

(d) Aon Corporation Outside Director Deferred Compensation Agreement by
and among Registrant and Registrant's directors who are not salaried
employees of Registrant or Registrant's affiliates.


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EXHIBIT INDEX

EXHIBIT NUMBER PAGE NUMBER OF
REGULATION SEQUENTIALLY
S-K, ITEM 601 NUMBERED COPY
- - - - - - - - - - - - - - - - - ------------- -------------

(e) Aon Stock Award Plan (as amended and restated through 1997) -
incorporated by reference to Exhibit 10(b) to the First Quarter 1997
Form 10-Q.

(f) First Amendment to the Aon Stock Award Plan as Amended and Restated
Through 1997 - incorporated by reference to exhibit 10(b) to the
First Quarter 1999 Form 10-Q.

(g) Amendment and Waiver Agreement dated as of November 4, 1991 among
the Registrant and each of Patrick G. Ryan, Shirley Ryan, Ryan
Enterprises Corporation and Harvey N. Medvin - incorporated by
reference to Exhibit 10(j) to the 1991 Form 10-K.

(h) Registration Rights Agreement dated November 2, 1992 by and
between the Registrant and Frank B. Hall & Co., Inc. - incorporated
by reference to Exhibit 4(c) to the Third Quarter 1992 Form 10-Q.

(i) Aon Corporation 1994 Amended and Restated Outside Director Stock
Award Plan - incorporated by reference to Exhibit 10(b) to the First
Quarter 1994 Form 10-Q.

(j) Aon Corporation 1995 Senior Officer Incentive Compensation Plan -
incorporated by reference to Exhibit 10(p) to the 1995 Form 10-K.

(k) Aon Deferred Compensation Plan and First Amendment to the Aon
Deferred Compensation Plan - incorporated by reference to Exhibit
10(q) to the 1995 Form 10-K.

(l) 1999 Aon Deferred Compensation Plan.

(m) Aon Severance Plan - incorporated by reference to Exhibit 10 to the
Registrant's Quarterly Report to the Securities and Exchange
Commission on Form 10-Q for the quarter ended June 30, 1997.

(n) Asset Purchase Agreement dated July 24, 1992 between the Registrant
and Frank B. Hall & Co. Inc. - incorporated by reference to Exhibit
10(c) to the Registrant's Quarterly Report on Form 10-Q for the
period ended June 30, 1992.

(o) Stock Purchase Agreement by and among the Registrant, Combined
Insurance Company of America, Union Fidelity Life Insurance Company
and General Electric Capital Corporation dated as of November 11,
1995 - incorporated by reference to Exhibit 10(s) of the 1995 Form
10-K.

(p) Stock Purchase Agreement by and among the Registrant; Combined
Insurance Company of America; The Life Insurance Company of
Virginia; Forth Financial Resources, Ltd.; Newco Properties, Inc.;
and General Electric Capital Corporation dated as of December 22,
1995 - incorporated by reference to Exhibit 10(t) to the 1995 Form
10-K.

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EXHIBIT INDEX

EXHIBIT NUMBER PAGE NUMBER OF
REGULATION SEQUENTIALLY
S-K, ITEM 601 NUMBERED COPY
- - - - - - - - - - - - - - - - - ------------- -------------

(q) Agreement and Plan of Merger among the Registrant, Purchaser and A&A
dated as of December 11, 1996 - incorporated by reference to Exhibit
(c)(1) to the Registrant's Schedule 14D-1 filed with the SEC on
December 16, 1996.

(r) First Amendment to Agreement and Plan of Merger dated as of January
7, 1997 among the Registrant, Purchaser and A&A - incorporated by
reference to Exhibit (c)(3) to Schedule 14D-1 filed by the
Registrant with the SEC on January 9, 1997.

(s) Employment Agreement dated June 1, 1993 by and among the Registrant,
Aon Risk Services, Inc. and Michael D. O'Halleran, incorporated by
reference to Exhibit 10(p) to the Registrant's Annual Report to the
Securities and Exchange Commission on Form 10-K for the year ended
December 31, 1998.

(12) Statements regarding Computation of Ratios.

(a) Statement regarding Computation of Ratio of Earnings to Fixed
Charges.

(b) Statement regarding Computation of Ratio of Earnings to
Combined Fixed Charges and Preferred Stock Dividends.

(13) Annual Report to Stockholders of the Registrant for the year ended
December 31, 1999.

(21) List of subsidiaries of the Registrant.


(23) Consent of Ernst & Young LLP to the incorporation by reference into Aon's
Annual Report on Form 10-K of their report included in the 1999 Annual
Report to Stockholders and into Aon's Registration Statement Nos.
33-27984, 33-42575, 33-59037, 333-21237, 333-50607, 333-55773 and
333-78723.

(99) Annual Report to the Securities and Exchange Commission on Form 11-K for
the Aon Savings Plan for the year ended December 31, 1999 - to be filed by
amendment as provided in Rule 15d-21(b).

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