SECURITIES AND EXCHANGE COMMISSION
                              Washington, DC 20549



                                    FORM 8-K

                             Current Report Pursuant
                          to Section 13 or 15(d) of the

                         Securities Exchange Act of 1934



    Date of report (Date of earliest event reported)        May 18, 2000
                                                        ------------------------



                               UNOCAL CORPORATION
- --------------------------------------------------------------------------------
             (Exact name of registrant as specified in its charter)



                                    Delaware

- --------------------------------------------------------------------------------
                 (State or Other Jurisdiction of Incorporation)



    1-8483                                   95-3825062
- --------------------------------------------------------------------------------
(Commission File Number)                (I.R.S. Employer Identification No.)



2141 Rosecrans Avenue, Suite 4000, El Segundo, California         90245
- --------------------------------------------------------------------------------

(Address of Principal Executive Offices)                       (Zip Code)



                                 (310) 726-7600

- --------------------------------------------------------------------------------
              (Registrant's Telephone Number, Including Area Code)


Item 5.      Other Events.
- --------------------------

Patent Case
- -----------

On May 18,  2000,  the United  States  Court of Appeals for the Federal  Circuit
denied a  petition  by six major oil  companies  to rehear  their  appeal of the
earlier decision validating the company's patent for reformulated gasoline.

In March,  a three judge panel of the Court upheld the validity of the company's
reformulated motor gasoline patent and confirmed the earlier jury award of 5-3/4
cents per gallon in damages for the infringement.

Following a 1997 trial in the U.S.  District  Court for the Central  District of
California  (Los  Angeles),  a jury had found the  patent was valid and that six
defendant  companies  had  infringed  the patent  with  respect to 1.19  billion
gallons,  or  29.1  percent  of  the  total  California   reformulated  gasoline
manufactured by the six defendant  companies between March 1, 1996, and July 31,
1996.  The jury also  awarded the company  5-3/4 cents per gallon in damages for
this  infringement.  The  jury's  award  for the  five-month  period  now  total
approximately $95 million, including interest and certain attorney's fees.

The "393" patent (No.  5,288,393) was awarded to the company by the U.S.  Patent
and  Trademark  Office  on  Feb.  22,  1994,  for  new,  useful  and  nonobvious
compositions  of  traditional  automotive  gasolines that  substantially  reduce
unwanted tailpipe emissions using current refining technology.  The compositions
outlined in the patent involve  specifications of various parameters in gasoline
manufacturing,  including Reid Vapor Pressure,  olefin content,  and the T50 and
T90 distillation points.

A series of  additional  patents has been granted to the company since the "393"
patent. These patents were an outgrowth of the earlier research and supplemented
the claims of the earlier patent.  The patents may have  application  throughout
the United States,  not just California.  None of the patents require or exclude
the use of MTBE.

The company believes that its patents may offer a significant  potential revenue
stream. With the conclusion of the appeal, the company will now ask the District
Court in Los Angeles to implement an earlier order for the  defendant  companies
to provide an  accounting  of their  infringement  of the "393" patent since the
five-month period covered by the trial.

Offer to Purchase Shares of Northrock Resources Ltd.
- ----------------------------------------------------

The company's Unocal Canada Management  Limited subsidiary will proceed with the
previously  announced  offer to purchase all the publicly  held common shares of
Northrock  Resources  Ltd.  (Northrock).  The  company  previously  announced  a
conditional  offer of $10.10  Canadian  dollars per share for the  approximately
21.9 million  shares,  or  approximately  52 percent,  of Northrock  that remain
outstanding.  The company's  Unocal Canada Resources  subsidiary  currently owns
19.6 million  shares,  or  approximately  48 percent,  of Northrock,  which were
acquired in transactions that closed in May and December of 1999.

Unocal Canada  Management  will be making this offer with the consent of, and in
full cooperation with,  Northrock.  Northrock's  board of directors  recommended
acceptance of the offer to Northrock's  shareholders after receiving a valuation
and fairness opinion from an independent  financial  advisor.  The offer for the
remaining  shares of Northrock will be subject to certain  conditions  including
obtaining all required regulatory  approvals and that a minimum of 90 percent of
the Northrock  shares not already owned by Unocal Canada  Resources are tendered
to the offer.  A take-over bid circular  containing  the offer will be mailed to
Northrock's shareholders of record as soon as reasonably possible.

                                      -1-


Forward looking statements  regarding any litigation and commercial  acquisition
activities  in  this  filing  are  based  on  assumptions   concerning   market,
operational,  competitive, regulatory,  environmental, and other considerations.
Actual  results  could differ  materially  as a result the  foregoing  and other
factors as outlined in Unocal's 1999 Form 10-K

Pursuant  to the  requirements  of the  Securities  Exchange  Act of  1934,  the
registrant  has duly  caused  this  report  to be  signed  on its  behalf by the
undersigned, thereunto duly authorized.

                                                UNOCAL CORPORATION
                                                (Registrant)





Date:  May 23, 2000                        By:  /s/ JOE D. CECIL
- -------------------------                       -------------------------------
                                                Joe D. Cecil
                                                Vice President and Comptroller


                                       -2-