Exhibit 10
                      AON 1998 EMPLOYEE STOCK PURCHASE PLAN


         Aon Corporation,  a Delaware  corporation,  hereby adopts this Aon 1998
Employee Stock Purchase Plan (the "Plan") as of the Effective Date. The purposes
of this Plan are as follows:

        (1)     To  assist   eligible   employees   of  the   Company   and  its
                Participating   Subsidiaries  in  acquiring  a  stock  ownership
                interest in the Company  pursuant to a plan which is intended to
                qualify as an "employee  stock  purchase plan" under Section 423
                of the Internal Revenue Code of 1986, as amended.

        (2)     To help eligible employees provide for their future security and
                to encourage them to remain in the employment of the Company and
                its Participating Subsidiaries.

Definitions.

         Whenever any of the following  terms is used in the Plan with the first
letter or letters  capitalized,  it shall have the following  meaning unless the
context  clearly  indicates  to the  contrary  (such  definitions  to be equally
applicable to both the singular and plural forms of the terms defined):

        (a)     "Code" means the Internal Revenue Code of 1986, as amended.

        (b)     "Committee" means the Organization and Compensation Committee of
                the Board of Directors of the Company.

        (c)     "Company" means Aon Corporation, a Delaware corporation.

        (d)     "Dates  of  Exercise"  means  the dates as of which an Option is
                exercised  and the Stock  subject to that  Option is  purchased.
                With  respect to any Option,  the Dates of Exercise are the last
                day of June and  December  on which  Stock is  traded on the New
                York  Stock  Exchange  during  the  Option  Period in which that
                Option was granted.

        (e)     "Date of Grant" means the date as of which an Option is granted,
                as set forth in paragraph 3(a).

        (f)     "EligibleCompensation"  means the  following  types of  earnings
                paid to an  Eligible  Employee  for his service on behalf of the
                Company:

                (i)     salary   and    fixed-based    compensation    including
                        compensation for overtime;

                (ii)    bonuses paid pursuant to periodic individual performance
                        appraisals and formal  contractual  bonus programs,  but
                        excluding other bonus and miscellaneous income; and



                (iii)   net commission,  renewal and override  compensation (but
                        excluding deferred commission payments).

        (g)     "Effective Date" means July 1,1998.

        (h)     "EligibleEmployee"  means  any  employee  of  the  Company  or a
                Participating Subsidiary who meets the following criteria:

                (i)     the employee does not,  immediately  after the Option is
                        granted,  own (within  the meaning of Section  423(b)(3)
                        and 424(d) of the Code) stock possessing five percent or
                        more of the total combined  voting power or value of all
                        classes of stock of the Company or of a Subsidiary;

                (ii)    the employee has completed  one year of  employment  for
                        the Company or a Subsidiary; and

                (iii)   the employee's  customary employment is 20 hours or more
                        a week.

        (i)     "Option"  means an option  granted under the Plan to an Eligible
                Employee to purchase shares of Stock.

        (j)     "Option  Period"  means  with  respect  to any Option the period
                beginning  upon the Date of Grant and  ending on the last day of
                June or  December  immediately  following  the  Date  of  Grant,
                whichever  is  earlier,  or  ending  on such  other  date as the
                Committee shall determine. No Option Period may exceed 27 months
                from the Date of Grant.

        (k)     "Option  Price"  with  respect to any Option has the meaning set
                forth in paragraph 4(b).

        (l)     "Participant"  means an Eligible  Employee who has complied with
                the provisions of paragraph 3(b).

        (m)     "Participating   Subsidiary"   means  any   present   or  future
                Subsidiary  that the  Committee  designates  to be  eligible  to
                participate  in the Plan,  and that elects to participate in the
                Plan.

        (n)     "Periodic  Deposit  Account" means the account  established  and
                maintained by the Company to which shall be credited pursuant to
                Section 3(c) amounts received from Participants for the purchase
                of Stock under the Plan.

        (o)     "Plan" means this Aon 1998 Employee Stock Purchase Plan.

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        (p)     "Plan Year" means the calendar year.

        (q)     "Stock" means shares of common stock, par value $1.00 per share,
                of the Company.

        (r)     "Stock  Purchase   Account"means  the  account  established  and
                maintained by the Company to which shall be credited pursuant to
                Section 4(c) Stock  purchased  upon  exercise of an Option under
                the Plan.

        (s)     "Subsidiary" means any corporation,  other than the Company,  in
                an unbroken chain of corporations beginning with the Company, if
                at  the  time  of  the  granting  of  the  Option,  each  of the
                corporations,  other than the last corporation,  in the unbroken
                chain owns stock  possessing  50% or more of the total  combined
                voting  power  of all  classes  of  stock  in  one of the  other
                corporations in such chain.


2.      Stock Subject to Plan.

        Subject to the  provisions of paragraph 8 (relating to  adjustment  upon
changes in the Stock),  the Stock which may be sold pursuant to Options  granted
under  the Plan  shall not  exceed in the  aggregate  five  million  (5,000,000)
shares,  and may be newly issued  shares or treasury  shares or shares bought in
the market, or otherwise, for purposes of the Plan.


3.      Grant of Options.

        (a)     General Statement.  The Company may grant Options under the Plan
                to all  Eligible  Employees  on January 1 and/or  July 1 of each
                Plan  Year  or  on  such  other  date  as  the  Committee  shall
                designate.  The term of each Option shall end on the last day of
                the Option  Period with  respect to which the Option is granted.
                With respect to each Option Period, each Eligible Employee shall
                be granted an Option, on the Date of Grant, for as many full and
                fractional shares of Stock as the Eligible Employee may purchase
                with up to 15% of the Eligible  Compensation  he or she receives
                during  the Option  Period (or during any  portion of the Option
                Period as the Eligible Employee may elect to participate).

        (b)     Election to  Participate.  Each Eligible  Employee who elects to
                participate  in the Plan shall  communicate  to the Company,  in
                accordance  with  procedures  established by the  Committee,  an
                election  to  participate  in  the  Plan  whereby  the  Eligible
                Employee  designates a stated whole percentage equaling at least
                1%, but no more than 15%,  of his or her  Eligible  Compensation
                during the Option Period to be deposited  periodically in his or
                her  Periodic  Deposit  Account  under   subparagraph  (c).  The
                cumulative  amount  deposited  in the Periodic  Deposit  Account
                during a Plan Year with respect to any Eligible Employee may not
                exceed  the  limitation  stated  in  subparagraph (d). 

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                A  Participant's   election  to  participate  in  the Plan shall
                continue in  effect  during  the  current and  subsequent Option
                Periods until changed pursuant to subparagraph 3(c).

        (c)     Periodic Deposit Accounts. The Company shall maintain a Periodic
                Deposit  Account for each  Participant  and shall credit to that
                account in U.S. dollars all amounts received under the Plan from
                the Participant.  No interest will be paid to any Participant or
                credited to his or her Periodic  Deposit  Account under the Plan
                with  respect  to  such  funds.   All  amounts   credited  to  a
                Participant's Periodic Deposit Account shall be used to purchase
                Stock   under   subparagraph   4(c);   provided,    however,   a
                Participant's  Periodic Deposit Account shall be refunded to him
                or her on receipt by the Company  prior to a Date of Exercise in
                accordance  with  procedures  established  by the Company,  of a
                Participant's request for such a refund.

                Credits to an Eligible Employee's Periodic Deposit Account shall
                be made by  payroll  deduction  or by  other  alternate  payment
                arrangements,   in   accordance   with   rules  and   procedures
                established by the Committee. An Eligible Employee may eliminate
                the periodic  credits to his or her Periodic Deposit Account for
                future  periods  by  filing a new  election  amount  at any time
                during an Option  Period.  The change shall become  effective in
                accordance with the Committee's  rules and procedures as soon as
                practicable  after the Company  receives the  election,  but the
                change will not affect the  amounts  deposited  with  respect to
                Eligible  Compensation  sooner  than the  Eligible  Compensation
                payable  with  respect to the next pay period  after the Company
                receives the authorization.

        (d)     Purchase Limitation.  No Eligible Employee shall be permitted to
                purchase  Stock under the Plan or under any other employee stock
                purchase  plan of the  Company  or of any  Subsidiary  which  is
                intended to qualify  under  Section  423 of the Code,  at a rate
                which exceeds $12,500 in fair market value of Stock  (determined
                by reference to the average of the high and low price of a share
                of Stock as quoted on the New York Stock Exchange on the Date of
                Grant) for each Option  Period in which any such Option  granted
                to such Participant is outstanding at any time. In the event the
                Committee  determines to make an Option Period shorter or longer
                than six  months,  the  foregoing  $12,500  limitation  shall be
                ratably adjusted but in no event shall the limit be greater than
                $25,000 in any one calendar year.  The Committee  shall have the
                discretion to impose a reduced  limitation on appropriate notice
                in advance of any Option Period.


4.      Exercise of Options.




        (a)     General Statement. On each Date of Exercise, the entire Periodic
                Deposit Account of each Participant shall be used to purchase at
                the Option Price whole and/or fractional shares of Stock subject

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                to  the  Option.  Each Participant automatically and without any
                act on his or her part will be deemed to have  exercised  his or
                her Option on each such Date of Exercise to the extent  that the
                amounts then  credited  to the  Participant's  Periodic  Deposit
                Account under the Plan are used to purchase Stock.

        (b)     Option Price Defined.  The Option Price per share of Stock to be
                paid by each  Participant  on each exercise of his or her Option
                shall be an amount in U.S.  dollars equal to the lower of 85% of
                the  fair  market  value  of a share  of Stock as of the Date of
                Grant or the applicable Date of Exercise.  The fair market value
                of a share of Stock as of an applicable Date of Grant or Date of
                Exercise  shall be the  average  of the high and low  price of a
                share of Stock as quoted on the New York Stock  Exchange on such
                date.

        (c)     Stock Purchase Accounts;  Stock Certificates.  The Company shall
                cause  to be  maintained  a  Stock  Purchase  Account  for  each
                Participant to reflect the Stock purchased under the Plan by the
                Participant.  Upon  exercise  of  an  Option  by  a  Participant
                pursuant to  subparagraph  4(a),  the Company  shall cause whole
                shares  of Stock  purchased  at that  time to be  issued  to the
                Participant's  Stock Purchase Account.  Any fractional shares of
                Stock resulting from the exercise of an Option shall be credited
                to an Eligible  Employee's  Periodic  Deposit Account to be used
                for the purchase of Stock in the next  following  Option  Period
                unless the Company has  received  prior  notice from an Eligible
                Employee of the  elimination  of periodic  credits in accordance
                with subparagraph 4 (c) of this Plan.

        (d)     Except as provided in paragraph 5,  certificates with respect to
                Stock held in a  Participant's  Stock Purchase  Account shall be
                issued only on request by the  Participant for a distribution of
                whole shares or when  necessary  to comply with the  transaction
                requirements  outside the United States. Upon issuance of such a
                Stock  certificate to a  Participant,  the  Participant's  Stock
                Purchase  Account  shall be  adjusted  to reflect  the number of
                shares of Stock distributed to the Participant.

5.      Rights on Retirement, Death, Termination of Employment.

        If a Participant retires, dies, or otherwise terminates  employment,  or
if the  corporation  that  employs a  participant  ceases to be a  Participating
Subsidiary, then to the extent practicable, no further amounts shall be credited
to the  Participant's  Periodic  Deposit Account from any pay due and owing with
respect to the participant after such retirement, death, or other termination of
employment.  All  amounts  credited  to such a  Participant's  Periodic  Deposit
Account  shall  be  returned  to the  Participant  or used on the  next  Date of
Exercise in that Option Period to purchase  Stock under  paragraph 4, based upon
the election by the  Participant or his or her personal  representative.  Such a
Participant's Stock Purchase Account shall be terminated, and Stock certificates
with respect to whole shares of Stock and cash with respect to fractional shares
of  Stock  shall  be  distributed  as soon as  practicable  after  such  Date of
Exercise.

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        Notwithstanding  anything in this Plan to the contrary,  a Participant's
Option shall not be  exercisable  more than three  months after the  Participant
retires or  otherwise  ceases to be employed  by the Company or a  Participating
Subsidiary,   including  as  a  result  of  the  corporation  ceasing  to  be  a
Participating Subsidiary, except to the extent permitted under Section 423(a) of
the Code.


6.      Restriction Upon Assignment of Options.

        An Option  granted under the Plan shall not be  transferrable  otherwise
than by will or the laws of descent and distribution,  and is exercisable during
the  Participant's  lifetime  only by the  Participant.  The  Company  will  not
recognize  and shall be under no duty to recognize  any  assignment or purported
assignment  by a  Participant,  other  than by will or the laws of  descent  and
distribution,  of the Participant's interest in the Plan or of his or her Option
or of any rights under his or her Option.


7.      No Rights of Stockholder Until Exercise of Option.

        A Participant  shall not be deemed to be a  stockholder  of the Company,
nor have any rights or privileges of a  stockholder,  with respect to the number
of shares of Stock subject to an Option. A Participant shall have the rights and
privileges  of  a  stockholder  of  the  Company  when,   but  not  until,   the
Participant's  Option is exercised  pursuant to subparagraph  4(a) and the Stock
purchased by the Participant at that time has been credited to the Participant's
Stock Purchase Account.


8.      Changes in the Stock; Adjustments of an Option.

        If, while any Options are outstanding,  the outstanding  shares of Stock
have  increased,  decreased,  changed  into,  or been  exchanged for a different
number or kind of shares or  securities  of the  Company,  or there has been any
other  change in the  capitalization  of the  Company,  through  reorganization,
merger,  recapitalization,  reclassification,  stock split, reverse stock split,
spinoff or similar transaction,  appropriate or proportionate adjustments may be
made by the  Committee in the number  and/or kind of shares which are subject to
purchase under  outstanding  Options and to the Option  Exercise Price or prices
applicable  to such  outstanding  Options,  including,  if the  Committee  deems
appropriate,  the  substitution of similar options to purchase shares of another
Company (with such other company's consent). In addition, in any such event, the
number  and/or kind of shares which may be offered in the Options  shall also be
proportionately  adjusted.  No adjustments to outstanding  Options shall be made
for dividends paid in the form of stock.

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9.      Use of Funds; Repurchase of Stock.

        All  funds  received  or held by the  Company  under  the  Plan  will be
included  in the  general  funds  of the  Company  free of any  trust  or  other
restriction and may be used for any corporate purpose.  The Company shall not be
required to  repurchase  from any Eligible  Employee  shares of Stock which such
Eligible Employee acquires under the Plan.


10.     Administration by Committee.

        (a)     Duties and Powers of The Committee.  It shall be the duty of the
                Committee to conduct the general  administration  of the Plan in
                accordance  with its  provisions.  The Committee  shall have the
                power to:

                (1)     determine  when  the  initial  and  subsequent   Options
                        Periods will commence;

                (2)     interpret the Plan and the Options;

                (3)     adopt such rules for the administration, interpretation,
                        and  application of the Plan as are consistent  with the
                        Plan and Section 423 of the Code; and

                (4)     interpret, amend, or revoke any such rules.


        In its absolute discretion, the Board of Directors of the Company may at
any time and from time to time  exercise  any and all  rights  and duties of the
Committee under the Plan. The Committee may delegate any of its responsibilities
under the Plan by  designating in writing other persons who carry out any or all
of such responsibilities.

        (b)     Majority  Rules.  The  Committee  shall act by a majority of its
                members in  office.  The  Committee  may act either by vote at a
                meeting or by a memorandum or other written instrument signed by
                a majority of the Committee.


        (c)     Compensation;  Professional Assistance;  Good Faith Actions. All
                expenses and liabilities incurred by members of the Committee in
                connection with the administration of the Plan shall be borne by
                the Company.  The Committee may employ  attorneys,  consultants,
                accountants,   appraisers,   brokers,  or  other  persons.   The
                Committee,  the Company, and its officers and directors shall be
                entitled to rely upon the advice, opinions, or valuations of any
                such  persons.  All actions  taken and all  interpretations  and
                determinations  made by the  Committee  in good  faith  shall be
                final and  binding  upon all  Participants,  the Company and all
                other  interested  persons.  No member of the Committee shall be
                personally    liable   for   any   action,    determination   or
                interpretation  made in good faith  with  respect to the Plan or
                the  Options,  and  all   members  of  the  Committee  shall  be

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                fully  protected  by  the Company in respect to any such action,
                determination or interpretation.


11.     No Rights as an Employee.

        Nothing in the Plan nor any Option shall be construed to give any person
(including  any  Eligible  Employee or  Participant)  the right to remain in the
employ of the Company or a Subsidiary  or to affect the right of the Company and
Subsidiaries  to terminate the employment of any person  (including any Eligible
Employee  or  Participant)  at any time with or  without  cause,  to the  extent
otherwise permitted under law.


12.     Amendment of the Plan.

        The Board of  Directors  of the  Company,  or its  delegate,  may amend,
suspend,  or terminate the Plan at any time;  provided that approval by the vote
of the holders of more than 50% of the outstanding  shares of the Stock entitled
to vote  shall be  required  to amend the Plan to reduce the  Exercise  Price or
increase the number of shares of Stock reserved for the Options under the Plan.


13.     Effect Upon Other Plans.

        The  adoption  of the Plan shall not affect  any other  compensation  or
incentive  plans in effect  for the  Company  or any  Subsidiary,  except to the
extent  required by law.  Nothing in this Plan shall be  construed  to limit the
right of the  Company or any  Subsidiary  (a) to  establish  any other  forms of
incentives or compensation for employees of the Company or any Subsidiary or (b)
to grant or assume options otherwise than under this Plan in connection with any
proper corporate purpose,  including, but not by way of limitation, the grant or
assumption of options in connection with the  acquisition,  by purchase,  lease,
merger,  consolidation  or otherwise,  of the  business,  stock or assets of any
corporation, firm or association.


14.     Notices.

         Any notice to be given under the terms of the Plan to the Company shall
be addressed to the Company in care of the  Committee and any notice to be given
to the Eligible  Employee shall be addressed to the Eligible  Employee at his or
her last  address as  reflected  in the  Company's  records.  By a notice  given
pursuant to this  paragraph,  either party may  hereafter  designate a different
address for notices to be given to it or the Eligible Employee. Any notice which
is required to be given to the Eligible Employee shall, if the Eligible Employee
is then deceased, be given to the Eligible Employee's personal representative if
such representative has previously informed the Company of his or her status and
address  by written  notice  under this  paragraph.  Any notice  shall have been

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deemed  duly  given  when  enclosed  in a properly  sealed  envelope  or wrapper
addressed  as  aforesaid,  deposited  (with  postage  prepaid) in a post office,
branch post  office,  or other  depository  regularly  maintained  by the United
States Post Office.


15.     Titles.

        Titles are provided herein for convenience  only and are not to serve as
a basis for interpretation or construction of the Plan.


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