<PAGE>
 
                                                                    Exhibit 10.8


                              Market Facts, Inc.
                First Amendment and Waiver To Credit Agreement


Harris Trust and Savings Bank
111 West Monroe Street
Chicago, Illinois 60603

Ladies and Gentlemen:

     Reference is hereby made to that certain Credit Agreement dated as of 
June 7, 1996 (the "Credit Agreement") by and among, Market Facts, Inc., a
Delaware corporation (the "Company"), and you (the "Bank"). All capitalized
terms used herein without definition shall have the same meanings herein as such
terms have in the Credit Agreement.

     The Company hereby applies to the Bank to increase the amount of the 
Revolving Credit Commitment, to increase the amount of the Revolving Loans 
permitted for conversion into the Term Loan and to make certain other 
corresponding amendments to the Credit Agreement, and the Bank is willing to do 
so under the terms and conditions set forth in this Amendment.

1.   WAIVER.

     The Company has informed the Bank that the Company acquired all the capital
stock of BAIGlobal, Inc. on July 31, 1997 for an initial purchase price of 
$6,000,000 and contingent future payments of an additional $5,000,000 (the 
"BAIGlobal Acquisition"). By virtue of the BAIGlobal Acquisition, the Company 
was not in compliance with Section 8.13 of the Credit Agreement. The Bank hereby
waives compliance with Section 8.13 of the Credit Agreement, to the extent, and 
only to the extent, such Section would otherwise disallow the BAIGlobal 
Acquisition, provided that this waiver shall not become effective unless and 
until the conditions precedent set forth in Section 4 have been satisfied.

2.   AMENDMENTS.

     2.01.  Section 1.1 of the Credit Agreement shall be amended by deleting the
amount "$7,000,000" appearing therein and by substituting the amount 
"$10,000,000" in lieu thereof.

     2.02.  Section 1.2 of the Credit Agreement shall be amended by deleting the
amount "$7,000,000" appearing therein and by substituting the amount
"$10,000,000" in lieu thereof.

     2.03.  Section 1.3 of the Credit Agreement shall be amended by deleting the
amount "$4,800,000" appearing therein and by substituting the amount
"$7,000,000" in lieu thereof.
<PAGE>
 
3.   REPLACEMENT OF NOTE.

     In replacement for the outstanding Revolving Credit Note dated June 14, 
1996 payable to the order of the Bank in the aggregate face principal amount of 
$7,000,000 (the "Existing Revolving Credit Note") pursuant to the Credit 
Agreement and the other changes made hereby, the Company shall execute and 
deliver to the Bank a new revolving credit note in the amount of $10,000,000 and
otherwise in the form (with appropriate insertions) annexed hereto as Exhibit A 
(the "New Revolving Credit Note") which shall substitute for the Existing 
Revolving Credit Note issued to the Bank and shall evidence all Revolving Loans 
now or hereafter outstanding from the Bank under the Revolving Credit. All 
references in the Credit Agreement or in any other instrument or document 
referring to the Existing Revolving Credit Note shall be deemed references to 
the New Revolving Credit Note.

4.   CONDITIONS PRECEDENT.

     The effectiveness of this Amendment is subject to the satisfaction of all 
of the following conditions precedent:

     4.01.  The Company and the Bank shall have executed and delivered this 
Amendment.

     4.02.  The Company shall have executed the New Revolving Credit Note in 
favor of the Bank in the form attached hereto as Exhibit A, to be dated as of 
the date of its issuance and in a face amount equal to $10,000,000.

     4.03.  No Default or Event of Default shall have occurred and be continuing
as of the date this Amendment would otherwise take effect.

     4.04.  Legal matters incident to the execution and delivery of this 
Amendment shall be satisfactory to the Bank and its counsel.

     Upon the effectiveness of this Amendment, the Bank shall promptly return to
the Company the Existing Revolving Credit Note which is being replaced by the 
New Revolving Credit Note contemplated by this Amendment.

5.   REPRESENTATIONS.

     In order to induce the Bank to execute and deliver this Amendment, the 
Company hereby represents to the Bank that as of the date hereof, the 
representations and warranties set forth in Section 6 of the Credit Agreement 
are and shall be and remain true and correct (except that for purposes of this 
paragraph, (i) the representations contained in Section 6.3 shall be deemed to 
include this Amendment as and when it refers to Loan Documents and (ii) the 
representations contained in Section 6.5 shall be deemed to refer to the most 
recent financial statements of the Company delivered to the Bank) and (except as
specifically waived herein) the Company is in full compliance with all of the 
terms and conditions of the Credit Agreement and no Default or Event of Default 
has occurred and is continuing under the Credit Agreement or shall result after 
giving effect to this Amendment.

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6.   MISCELLANEOUS.

     6.01.  Except as specifically amended herein, the Credit Agreement shall 
continue in full force and effect in accordance with its original terms. 
Reference to this specific Amendment need not be made in the Credit Agreement, 
the Notes, or any other instrument or document executed in connection therewith,
or in any certificate, letter or communication issued or made pursuant to or 
with respect to the Credit Agreement, any reference in any of such items to the 
Credit Agreement being sufficient to refer to the Credit Agreement as amended 
hereby.

     6.02.  This Amendment may be executed in any number of counterparts, and by
the different parties on different counterpart signature pages, all of which 
taken together shall constitute one and the same agreement. Any of the parties 
hereto may execute this Amendment by signing any such counterpart and each of 
such counterparts shall for all purposes be deemed to be an original. This 
Amendment shall be governed by the internal laws of the State of Illinois.

     6.03.  The Company agrees to pay all reasonable out-of-pocket costs and 
expenses incurred by the Bank in connection with the preparation, execution and 
delivery of this Amendment and the documents and transactions contemplated 
hereby, including the reasonable fees and expenses of counsel for the Bank with 
respect to the foregoing.

     Dated as of September 4, 1997.

                                          MARKET FACTS, INC.


                                          By /s/ Timothy Sullivan
                                             ---------------------------------
                                             Its Senior Vice President
                                                 -----------------------------

     Accepted and agreed to in Chicago, Illinois as of the date and year last 
above written.

                                          HARRIS TRUST AND SAVINGS BANK


                                          By /s/ Dan Sabol
                                             ---------------------------------
                                             Its Vice President
                                                 -----------------------------

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<PAGE>
 
                              Market Facts, Inc.
                             Revolving Credit Note


                                                               Chicago, Illinois
$10,000,000                                                    September 4, 1997

     On the Revolving Credit Termination Date, for value received, the 
undersigned, MARKET FACTS, INC., a Delaware corporation (the "Company"), hereby 
promises to pay to the order of HARRIS TRUST AND SAVINGS BANK (the "Bank") at 
its office at 111 West Monroe Street, Chicago, Illinois, the principal sum of 
(i) Ten Million and no/100 Dollars ($10,000,000), or (ii) such lesser amount as 
may at the time of the maturity hereof, whether by acceleration or otherwise, be
the aggregate unpaid principal amount of all Revolving Loans owing from the 
Company to the Bank under the Revolving Credit provided for in the Credit 
Agreement hereinafter mentioned.

     This Note evidences Revolving Loans made and to be made to the Company by 
the Bank under the Revolving Credit provided for under that certain Credit 
Agreement dated as of June 7, 1996, between the Company and the Bank (said 
Credit Agreement, as the same may be amended, modified or restated from time to 
time, being referred to herein as the "Credit Agreement"), and the Company 
hereby promises to pay interest at the office described above on such Revolving 
Loans evidenced hereby at the rates and at the times and in the manner specified
therefor in the Credit Agreement.

     Each Revolving Loan made under the Revolving Credit against this Note, any 
repayment of principal hereon, the status of each such Revolving Loan from time 
to time as part of the Domestic Rate Portion or a LIBOR Portion and, in the case
of any LIBOR Portion, the interest rate and Interest Period applicable thereto 
shall be endorsed by the holder hereof on a schedule to this Note or recorded on
the books and records of the holder hereof (provided that such entries shall be 
endorsed on a schedule to this Note prior to any negotiation hereof). The 
Company agrees that in any action or proceeding instituted to collect or enforce
collection of this Note, the entries endorsed on a schedule to this Note or 
recorded on the books and records of the holder hereof shall be prima facie 
evidence of the unpaid principal balance of this Note, the status of each 
Revolving Loan from time to time as part of the Domestic Rate Portion or a LIBOR
Portion and, in the case of any LIBOR Portion, the interest rate and Interest 
Period applicable thereto absent manifest error.

     This Note is issued by the Company under the terms and provisions of the 
Credit Agreement, and this Note and the holder hereof are entitled to all of the
benefits and security provided for thereby or referred to therein, to which 
reference is hereby made for a statement thereof. This Note may be declared to 
be, or be and become, due prior to its expressed maturity and voluntary 
prepayments may be made hereon, all in the events, on the terms and with the 
effects provided in the Credit Agreement. All capitalized terms used
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herein without definition shall have the same meanings herein as such terms are
defined in the Credit Agreement.

     This Note is issued in substitution for and in replacement of that certain
Revolving Credit Note of the Company dated June 14, 1996 payable to the order of
the Bank in the face principal amount of $7,000,000.

     The Company hereby promises to pay all reasonable out-of-pocket costs and
expenses (including attorneys' fees) suffered or incurred by the holder hereof
in collecting this Note or enforcing any rights in any collateral therefor. The
Company hereby waives presentment for payment and demand. This Note shall be
construed in accordance with, and governed by, the internal laws of the State of
Illinois without regard to principles of conflicts of laws.

                                        MARKET FACTS, INC.


                                        By: /s/ Timothy J. Sullivan
                                            --------------------------    
                                        Name: Timothy J. Sullivan
                                              ------------------------    
                                        Title: Senior Vice President
                                               ----------------------- 

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