Senior Debt Securities

EXHIBIT 4.1



                          COSTCO WHOLESALE CORPORATION

                                       and

                   U.S. BANK National Association, as Trustee

                           --------------------------

                             Senior Debt Securities

                          First Supplemental Indenture

                           ---------------------------

                           Dated as of March 20, 2002








                          First Supplemental Indenture

     THIS FIRST SUPPLEMENTAL  INDENTURE,  dated as of March 20, 2002 (the "First
Supplemental  Indenture"),  between COSTCO WHOLESALE CORPORATION,  a corporation
duly  organized and existing  under the laws of the State of Washington  (herein
called the "Company"), having its principal offices at 000 Xxxx Xxxxx, Xxxxxxxx,
Xxxxxxxxxx 00000, and U.S. BANK National Association,  as Trustee (herein called
the "Trustee"),  under the Indenture,  dated as of October 26, 2001, between the
Company and the Trustee (the "Base Indenture").

                             RECITALS OF THE COMPANY

     Whereas,  the Company  executed  and  delivered  the Base  Indenture to the
Trustee to provide for the issuance  from time to time of the  Company's  senior
debt securities to be issued in one or more series as might be determined by the
Company under the Base Indenture;

     Whereas,  the Base Indenture  provides that the Company and the Trustee may
enter into a  supplemental  indenture for the purposes of adding terms of senior
debt securities or curing  ambiguities or inconsistencies in such Base Indenture
or making other provisions;

     Whereas, the Company has duly authorized the execution and delivery of this
First  Supplemental  Indenture to provide for the issuance  from time to time of
its senior debt securities,  to be issued in one or more series as in this First
Supplemental Indenture provided; and

     Whereas,  all things necessary to make this First Supplemental  Indenture a
valid agreement of the Company, in accordance with its terms, have been done.

     NOW, THEREFORE, THIS FIRST SUPPLEMENTAL INDENTURE WITNESSETH:

     For and in consideration of the premises and the purchase of the Securities
by the Holders thereof,  it is mutually covenanted and agreed, for the equal and
proportionate benefit of all Holders of the Securities or of any series thereof,
as follows:

Paragraph A. INCORPORATION BY REFERENCE

     Articles  I  through  XV  of  the  Costco  Wholesale  Corporation  Standard
Multiple-Series  Indenture  Provisions,  dated as of March 20,  2002,  a copy of
which is  attached  hereto  as Annex  "A",  are  hereby  incorporated  herein by
reference with the same force and effect as though fully set out herein.

                            [Signature Pages Follow]









         IN WITNESS WHEREOF, the parties hereto have caused this First
Supplemental Indenture to be duly executed and attested as of the day and year
first above written.

                                 COSTCO WHOLESALE CORPORATION



                                 By
                                    -------------------------------------------
                                    Executive Vice President

Attest



---------------------------
Title:  Assistant Secretary



                                  U.S. BANK National Association,
                                    as Trustee


                                  By
                                     -----------------------------------------
                                     Title: Authorized Signatory

Attest



---------------------------
Title:  Assistant Secretary



                   First Supplemental Indenture Signature Page