Filed Pursuant to
                                                                  Rule 424(b)(3)
                                                               File No. 33-63719


                      Supplement to the Unocal Corporation
              Dividend Reinvestment and Common Stock Purchase Plan
                         Prospectus dated August 2, 1999




     Mellon  Bank,  N.A.,  has  succeeded  to The  Chase  Manhattan  Bank as the
administrator  for the Dividend  Reinvestment  and Common Stock  Purchase  Plan.
Therefore,  all  references to The Chase  Manhattan  Bank in the  Prospectus are
changed to Mellon Bank.

     As a result of a change in its ownership, ChaseMellon Shareholder Services,
L.L.C.  has changed its name to Mellon  Investor  Services LLC.  Therefore,  all
references to  ChaseMellon  Shareholder  Services  acting in various  capacities
described in the Prospectus are changed to Mellon Investor Services.

     The paragraph  commencing  at the  bottom of page 5 of the  Prospectus  is
deleted.

     Mellon Investor  Services is also the Rights Agent under a Rights Agreement
dated January 29, 2000,  which replaced the Rights  Agreement  dated January 29,
1990,  formerly referred to in the paragraph  commencing at the bottom of page 5
of the Prospectus.


July 25, 2001