EXHIBIT 99(a)

                    REVOCABLE PROXY OF CASCADE BANCORP, INC.
                        SPECIAL MEETING OF SHAREHOLDERS
                                  
                               November 20, 1997      
    
     The undersigned hereby appoints Donald W. Lisko and Thomas L. Matson, and
each of them (with full power to act alone) as proxies, with full power of
substitution, and hereby authorizes them to represent and to vote, as designated
below, all the shares of Cascade Bancorp, Inc. ("Cascade") common stock, $1.00
par value per share, held of record by the undersigned on October 15, 1997, at
a Special Meeting of Shareholders to be held at Cascade's principal office
located at 25 - 16th Street N.E., Auburn, Washington on November 20, 1997, at
7:30 p.m., local time, and at any and all adjournments of such Meeting, as
follows:      


                                                                                    
 1.   Merger Proposal.  A proposal to approve the merger of            FOR      AGAINST      ABSTAIN
      Cascade with and into Columbia Banking System, Inc.,             ---      -------      -------
      with Columbia Banking System, Inc., as the survivor,            [   ]      [   ]        [   ]
      pursuant to the Agreement and Plan of Reorganization and 
      Merger dated as of June 30, 1997.


        THE BOARD OF DIRECTORS UNANIMOUSLY RECOMMENDS A VOTE "FOR" THE
                                ABOVE PROPOSAL.

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THIS PROXY WILL BE VOTED AS DIRECTED, BUT IF NO INSTRUCTIONS ARE SPECIFIED, THIS
PROXY WILL BE VOTED FOR THE PROPOSITION STATED. IF ANY OTHER BUSINESS IS
PRESENTED AT SUCH MEETING, THIS PROXY WILL BE VOTED BY THOSE NAMED IN THIS PROXY
IN THEIR BEST JUDGMENT. AT THE PRESENT TIME, THE BOARD OF DIRECTORS KNOWS OF NO
OTHER BUSINESS TO BE PRESENTED AT THE MEETING. HOWEVER, IF ANY OTHER MATTERS ARE
PROPERLY PRESENTED AT THE MEETING, THIS PROXY WILL BE VOTED IN ACCORDANCE WITH
THE RECOMMENDATIONS OF MANAGEMENT. THIS PROXY IS SOLICITED BY THE BOARD OF
DIRECTORS.
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     Please sign exactly as your name appears on this form of proxy.  When
signing as attorney, executor, administrator, trustee or guardian, please give
your full title.  If shares are held jointly, each holder must sign.  In the
event that you are present and elect to vote at the Special Meeting or at any
adjournment thereof, you must notify the Secretary of Cascade at the Special
Meeting of your decision to terminate this proxy, and then the power of said
attorneys and proxies shall be deemed terminated and of no further force and
effect.

    
     The undersigned acknowledges that prior to the execution of this proxy, he
or she received from Cascade, notice of the Special Meeting and a Joint Proxy
Statement/Prospectus dated October 16, 1997.     

Dated: ____________________, 1997


  __________________________________       ___________________________________
  PRINT NAME OF SHAREHOLDER                PRINT NAME OF SHAREHOLDER
 
 
  __________________________________       ___________________________________
  SIGNATURE OF SHAREHOLDER                 SIGNATURE OF SHAREHOLDER


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   PLEASE COMPLETE, DATE, SIGN AND MAIL THIS PROXY PROMPTLY IN THE ENCLOSED
                           POSTAGE PREPAID ENVELOPE.
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