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                                 EXHIBIT 10 (tt)

              FIRST AMENDMENT TO 1996 INCENTIVE STOCK OPTION PLAN
                              DATED JULY 23, 1998


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                               FIRST AMENDMENT
                                       TO
                      CDW 1996 INCENTIVE STOCK OPTION PLAN


     This First  Amendment  to the CDW 1996  Incentive  Stock  Option Plan (this
"Amendment") is made as of this 23rd day of July, 1998.

                              W I T N E S S E T H:

     WHEREAS, on the 14th day of November,  1996, CDW Computer Centers, Inc., an
Illinois  corporation  (the  "Company"),  adopted the CDW 1996  Incentive  Stock
Option Plan  pursuant to which the Company is  authorized to grant stock options
to the Company's directors, officers, employees and consultants (the "Plan");

     WHEREAS,  the  Compensation  and Stock Option Committee of the Company (the
"Committee")  deems it to be in the best  interests of the Company that the Plan
be amended so as to clarify that the Plan may be used to grant stock  options to
directors, officers, employees and consultants of the Company's subsidiaries and
affiliates and such other changes as reflected herein; and

     WHEREAS,  the  Committee  is  vested  with the  ability  to amend  the Plan
pursuant to Section 12 thereof.

     NOW, THEREFORE, in accordance with the powers vested in the Committee under
the Plan, the Plan shall be amended as follows:

     7.  Section  1(a) of the Plan shall be restated in its entirety as follows:
"The  purpose  of the CDW 1996  Incentive  Stock  Option  Plan (the  "Plan")  as
hereinafter  set forth,  is to enable CDW Computer  Centers,  Inc.,  an Illinois
corporation  (the "Company"),  and its subsidiaries and affiliates,  to attract,
retain and reward all directors, officers, employees and consultants by offering
them an  opportunity  to  have a  greater  proprietary  interest  in and  closer
identity with the Company and with its financial  success and thereby  encourage
such individuals to remain in the employ or service of the Company or to attract
to the Company people of exceptional experience and ability."

     8. The first  sentence of Section 3(a) of the Plan shall be restated in its
entirety as follows:  "Options may be granted under this Plan to all  directors,
officers,  employees and consultants of the Company, its subsidiaries and/or its
affiliates (collectively, "Employees")."

     9. The first sentence of Section  5(f)(i) shall be restated in its entirety
as  follows:  "In the event that an  Employee  shall cease to be employed by the
Company  for any  reason  other  than  death,  Disability  (as  defined  below),
Retirement (as defined below) or for cause (as defined  below),  the Employee or
personal  representative  shall have the right,  subject  to the  provisions  of
Section  5(b),  5(j) and 6 hereof,  to  exercise  his or her Options at any time
within three (3) months after such  cessation of employment  but only as to such
number of Shares as to which his or her Options were vested and  exercisable  at
the date of such cessation of employment."

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     10.  Section  5(f)(i)  shall be  amended  by adding  the  following  as new
subsection (D):

     "(D) if  cessation of  employment  occurs by reason of the  Retirement  (as
     hereinafter defined) of the Employee,  the Options granted to such Employee
     shall continue to vest in accordance with their original  vesting  schedule
     and Employee  shall be entitled to exercise said Options as if the Employee
     were still employed by the Company."

     11.  Section  5(f)(ii)  shall be amended by replacing the term  "Agreement"
throughout said section with the term "Plan".

     12.  Section  5(f)  shall be  amended  by  adding  the  following  as a new
subsection 5(f)(iii):

     ""Retirement"  for purposes of this Plan shall be defined as the  voluntary
     termination  of employment by the Employee at any time after  attaining age
     62 and provided  that said Employee has been  continuously  employed by the
     Company  for a period  of not less  than ten (10)  years at the time of the
     Employee's voluntary termination."

     13. A new Section 5(j) shall be added as follows:

          (j)  Non-Competition.  In the event that an Employee  is employed  by,
     receives compensation from or otherwise is associated with or has agreed in
     principle to be employed by or to receive compensation from or otherwise be
     associated  as  an  officer,   agent,  director,   employee,   shareholder,
     consultant,  or otherwise with a Competitor (as hereinafter defined) of the
     Company  at any  time  prior  to the  expiration  of the  Options:  (i) all
     unexercised  Options  shall be forfeited  and (ii) any Option  Proceeds (as
     hereinafter  defined) shall be immediately  due and payable by the Employee
     to the Company.  For purposes of this  Section,  "Competitor"  shall be any
     entity or person which  engages for any portion of its business in the sale
     of  personal  computer  products to  residents  of the United  States.  For
     purposes of this Section,  "Option  Proceeds" shall mean (i) the difference
     between (A) the per share closing  price of the  Company's  Common Stock as
     reported on the Nasdaq  Stock  Market or such other  reported  value of the
     Common Stock as shall be specified by the Committee at the date of exercise
     and (B) the per share exercise price of the Option,  multiplied by (ii) the
     number of shares acquired  pursuant to any exercise of Options issued under
     this  Plan  which  occurs  after  the date 24  months  prior to the date of
     termination  of employment  with the Company.  The remedy  provided by this
     Section  shall be in  addition to and not in lieu of any rights or remedies
     which  Company may have  against the Employee in respect of a breach by the
     Employee of any duty or obligation to the Company.

     14. The Amendment shall become effective as of the date set forth above.

     IN WITNESS  WHEREOF,  the undersigned have executed this First Amendment to
the CDW 1996 Incentive  Stock Option Plan as of this 23rd day of July,  1998, in
Vernon Hills, State of Illinois.


                Signature                                 Title
                ---------                                 -----


         /s/ Michelle L. Collins             Director and Member of Compensation
         Michelle L. Collins                 and Stock Option Committee

         /s/ Joseph Levy, Jr.                Director and Member of Compensation
         Joseph Levy, Jr.                    and Stock Option Committee

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