December 31, 1999


William W. Sherertz, President
BARRETT BUSINESS SERVICES, INC.
4724 SW Macadam Avenue
Portland, OR 97201

Dear Mr. Sherertz:

         This  letter  amendment  (this  "Amendment")  is to confirm the changes
agreed upon between Wells Fargo Bank, National  Association ("Bank") and BARRETT
BUSINESS SERVICES, INC. ("Borrower") to the terms and conditions of that certain
letter agreement  between Bank and Borrower dated as of May 31, 1998, as amended
from time to time (the "Agreement"). For valuable consideration, the receipt and
sufficiency  of which are hereby  acknowledged,  Bank and Borrower  hereby agree
that the Agreement shall be amended as follows to reflect said changes.

         1.   Paragraph  V.8.  is  hereby  deleted  in  its  entirety,  and  the
following substituted therefor:

                   "8.  Financial   Condition.   Maintain  Borrower's  financial
              condition  as  follows   using   generally   accepted   accounting
              principles  consistently  applied and used consistently with prior
              practices  (except  to the  extent  modified  by  the  definitions
              herein):

                   (a) Current Ratio as of the end of each fiscal quarter not at
              any time less than 1.15 to 1.0,  with "Current  Ratio"  defined as
              total current assets divided by total current liabilities.

                   (b) EBITDA  not less than  $10,000,000.00  as of each  fiscal
              quarter  end,  on a trailing  four-quarters  basis  including  the
              current  quarter then ended,  with "EBITDA"  defined as net profit
              before tax plus  interest  expense  (net of  capitalized  interest
              expense), depreciation expense and amortization expense.

                   (c) Funded Debt to EBITDA  Ratio as of the end of each fiscal
              quarter not more than 2.25 to 1.0,  with "Funded  Debt" defined as
              all  borrowed  funds  plus the  amount  of all  capitalized  lease
              obligations of Borrower."

         2.   Except as specifically  provided herein,  all terms and conditions
of  the  Agreement   remain  in  full  force  and  effect,   without  waiver  or
modification.  All terms  defined in the  Agreement  shall have the same meaning
when used herein.  This Amendment and the Agreement  shall be read together,  as
one document.

         3.   Borrower  hereby  remakes  all   representations   and  warranties
contained in the  Agreement  and  reaffirms  all  covenants  set forth  therein.
Borrower further certifies that as of the date of Borrower's  acknowledgment set
forth  below  there  exists no  default or  defined  event of default  under the
Agreement  or any  promissory  note or other  contract,  instrument  or document
executed in connection therewith, nor any condition, act or event which with the
giving of notice or the passage of time or both would  constitute such a default
or defined event of default.

BARRETT BUSINESS SERVICES, INC.
December 31, 1999
Page 2

UNDER OREGON LAW, MOST  AGREEMENTS,  PROMISES AND COMMITMENTS MADE BY BANK AFTER
OCTOBER 3, 1989 CONCERNING  LOANS AND OTHER CREDIT  EXTENSIONS WHICH ARE NOT FOR
PERSONAL,  FAMILY OR  HOUSEHOLD  PURPOSES  OR SECURED  SOLELY BY THE  BORROWER'S
RESIDENCE MUST BE IN WRITING,  EXPRESS CONSIDERATION AND BE SIGNED BY BANK TO BE
ENFORCEABLE.

         Your  acknowledgment  of this Amendment shall constitute  acceptance of
the foregoing terms and conditions.


                                   Sincerely,

                                   WELLS FARGO BANK,
                                     NATIONAL ASSOCIATION


                                   By: /s/ Julie Wilson
                                       ----------------------
                                       Julie Wilson
                                       Vice President


Acknowledged and accepted as of 1/26/00:
                                --------

BARRETT BUSINESS SERVICES, INC.


By:  /s/ William W. Sherertz
     --------------------------
     William W. Sherertz
     President