SUPPLEMENT DATED FEBRUARY 19, 1999
         TO SUPPLEMENTS DATED FEBRUARY 4, 1999, OCTOBER 26, OCTOBER 13,
         AUGUST 17, JULY 16, MAY 22, MAY 4, APRIL 3, APRIL 1, MARCH 23,
            FEBRUARY 25, AND JANUARY 21, 1998, AND DECEMBER 19, 1997,
                      TO PROSPECTUS DATED NOVEMBER 26, 1997

                             COSTCO COMPANIES, INC.

         The following  table sets forth  information as of February 19, 1999 as
to the security ownership of persons not named as Selling Securityholders in the
Prospectus and Prospectus Supplements.  The table also sets forth information as
to  additional  securities  that were  acquired by  Donaldson  Lufkin & Jenrette
Securities  Corporation ("DLJ") and Merrill Lynch, Pierce,  Fenner & Smith, Inc.
("Merrill Lynch") since each was last named as a Selling Securityholder. Amounts
shown for DLJ and  Merrill  Lynch are not  adjusted  for any sales that they may
have made  pursuant to the  Registration  Statement.  DLJ has  provided and will
continue to provide financial  advisory services to Costco Companies,  Inc. (the
"Company")  for which DLJ has  received  customary  fees.  Hamilton E. James,  a
Managing  Director of DLJ, is a member of the Board of Directors of the Company.
Merrill  Lynch  provides  certain  brokerage  services to the Company in Canada.
Except  as  set  forth  for  DLJ  and  Merrill   Lynch,   none  of  the  Selling
Securityholders listed below has had a material relationship with the Company or
any of its predecessors or affiliates within the past three years.

                             Face Amount of Notes     Shares of Common Stock
                                 Owned Prior                Owned Prior 
 Selling Securityholder         to Offering ($)            to Offering 1

CMAC                                   $250,000              2,838
COVA Bond Debenture Fund               $500,000              5,677
Donaldson Lufkin & Jenrette
 Securities Corporation            $100,320,000 2        1,139,083 2
Finger Lake Blue Cross                 $500,000              5,677
IL Annuity and Insurance Co.        $40,000,000            454,180
Merrill Lynch, Pierce, Fenner
 & Smith, Inc.                      $64,889,000 2          736,782 2
Oxford Fund                          $1,500,000             17,031

1        Includes the Shares into which the Notes are convertible.

2        Includes securities previously registered.

              The date of this Prospectus Supplement is February 19, 1999