==============================================================================
                       SECURITIES AND EXCHANGE COMMISSION
==============================================================================
                             Washington, D.C. 20549
                                 -----------
                                  SCHEDULE TO/A
                                 (RULE 14D-100)

          TENDER OFFER STATEMENT UNDER SECTION 14(d)(1) or 13(e)(1)
                    OF THE SECURITIES EXCHANGE ACT OF 1934


                                (Amendment No. 3)

                              PURE RESOURCES, INC.
                            (Name of Subject Company)

                               UNOCAL CORPORATION
                         UNION OIL COMPANY OF CALIFORNIA
                       (Name of Filing Persons--Offerors)

                   COMMON STOCK, PAR VALUE $0.01 PER SHARE
                         (Title of Class of Securities)

                                   74622E 10 2
                      (CUSIP Number of Class of Securities)

                          Barry A. L. Hoffman, Esq.
                             Deputy General Counsel
                               Unocal Corporation
                        2141 Rosecrans Avenue, Suite 4000
                          El Segundo, California 90245
                                 (310) 726-7600
           (Name, Address and Telephone Number of Person Authorized
      to Receive Notices and Communications on Behalf of Filing Persons)

                                   -Copies to-
                                 Daniel A. Neff
                                Elliott V. Stein
                         Wachtell, Lipton, Rosen & Katz
                               51 West 52nd Street
                               New York, NY 10019
                                 (212) 403-1000
                                   -----------

                            CALCULATION OF FILING FEE


                  Transaction Valuation*       Amount of Filing Fee
           ----------------------------------------------------------
                     $553,431,082                    $50,916
           ----------------------------------------------------------

*  Estimated solely for the purpose of calculating the filing fee pursuant to
   Rule 0-11 under the Securities Exchange Act of 1934, as amended, based on the
   product of (i) 23.20 the average of the high and low sales prices of Pure
   Resources, Inc.'s common stock and (ii) 23,854,788, the maximum number of
   shares to be acquired pursuant to this offer.

[X]Check the box if any part of the fee is offset as provided by Rule
   0-11(a)(2) and identify the filing with which the offsetting fee was
   previously paid. Identify the previous filing by registration statement
   number, or the Form or Schedule and the date of its filing.
         Amount Previously Paid:  $50,916.Filing Party:  Unocal Corporation.
         Form or Registration No.:  Form S-4.   Date Filed:  September 4, 2002
[_]Check the box if the filing relates solely to preliminary communications
   made before the commencement of a tender offer.
Check the appropriate boxes below to designate any transactions to which the
   statement relates:
[X]   third-party tender offer subject to Rule 14d-1.
[_]   issuer tender offer subject to Rule 13e-4.
[_]   going-private transaction subject to Rule 13e-3.
[X]   amendment to Schedule 13D under Rule 13d-2.
Check the following box if the filing is a final amendment reporting the results
   of the tender offer: [_]
==============================================================================










                                  SCHEDULE 13D

-----------------------------                      -----------------------------
   CUSIP NO. 74622E 10 2                                   Page 2 of 6
-----------------------------                      -----------------------------

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

1.      NAME OF REPORTING PERSON
        S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON

           Unocal Corporation
           95-3825062

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

2.       CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP
                                                                         (a) [ ]
                                                                         (b) [ ]
--------------------------------------------------------------------------------

3.       SEC USE ONLY

--------------------------------------------------------------------------------
4.       SOURCE OF FUNDS

         AF
--------------------------------------------------------------------------------

5.       CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED
         PURSUANT TO ITEMS 2(d) OR 2(e)
                                                                             [ ]
--------------------------------------------------------------------------------

6.       CITIZENSHIP OR PLACE OF ORGANIZATION

         Delaware
--------------------------------------------------------------------------------
    NUMBER OF               7.  SOLE VOTING POWER
                                -0-
     SHARES
                    ------------------------------------------------------------
  BENEFICIALLY
                            8.  SHARED VOTING POWER
    OWNED BY                    35,890,333 (1)

      EACH          ------------------------------------------------------------
                            9.  SOLE DISPOSITIVE POWER
   REPORTING                    32,709,067

  PERSON WITH       ------------------------------------------------------------
                           10.  SHARED DISPOSITIVE POWER
                                -0-

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

11.      AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
         35,890,333 (*)

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

12.      CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES
         CERTAIN SHARES
                                                                             [ ]
--------------------------------------------------------------------------------

13.      PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)
         71.3%

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

14.      TYPE OF REPORTING PERSON REPORTING

         C0
--------------------------------------------------------------------------------


------------------
(1) Includes 32,709,067 shares directly owned by Union Oil Company of
California, and 3,181,266 shares beneficially owned by Jack D. Hightower, with
respect to which the reporting persons may be deemed to share voting control by
virtue of the Voting Agreement (as described on the reporting persons joint
Statement on Schedule 13D, as amended, which is incorporated herein by
reference).




       SCHEDULE 13D

-----------------------------                      -----------------------------
   CUSIP NO. 74622E 10 2                                   Page 3 of 6
-----------------------------                      -----------------------------

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

1.      NAME OF REPORTING PERSON
        S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON

           Union Oil Company of California
           95-1315450

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

2.       CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP
                                                                         (a) [ ]
                                                                         (b) [ ]
--------------------------------------------------------------------------------

3.       SEC USE ONLY

--------------------------------------------------------------------------------
4.       SOURCE OF FUNDS

         OO
--------------------------------------------------------------------------------

5.       CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED
         PURSUANT TO ITEMS 2(d) OR 2(e)
                                                                             [ ]
--------------------------------------------------------------------------------

6.       CITIZENSHIP OR PLACE OF ORGANIZATION

         California
--------------------------------------------------------------------------------
    NUMBER OF               7.  SOLE VOTING POWER
                                -0-
     SHARES
                    ------------------------------------------------------------
  BENEFICIALLY
                            8.  SHARED VOTING POWER
    OWNED BY                    35,890,333 (2)

      EACH          ------------------------------------------------------------
                            9.  SOLE DISPOSITIVE POWER
   REPORTING                    32,709,067

  PERSON WITH       ------------------------------------------------------------
                           10.  SHARED DISPOSITIVE POWER
                                -0-

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

11.      AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
         35,890,333 (*)

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

12.      CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES
         CERTAIN SHARES
                                                                             [ ]
--------------------------------------------------------------------------------

13.      PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)
         71.3%

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

14.      TYPE OF REPORTING PERSON REPORTING

         CO
--------------------------------------------------------------------------------


-------------------
(2) Includes 32,709,067 shares directly owned by Union Oil Company of
California, and 3,181,266 shares beneficially owned by Jack D. Hightower, with
respect to which the reporting persons may be deemed to share voting control by
virtue of the Voting Agreement (as described on the reporting persons joint
Statement on Schedule 13D, as amended, which is incorporated herein by
reference).










            This Amendment No. 3 to the Tender Offer Statement on Schedule TO
and combined Amendment No. 5 to the joint Statement on Schedule 13D (together
with the Initial Schedule TO (as defined below), as previously amended and as
amended hereby, the "Schedule TO") are filed by Unocal Corporation, a Delaware
corporation ("Unocal"), and its wholly owned subsidiary Union Oil Company of
California, a California corporation ("Union Oil", together with Unocal, the
"Reporting Persons"). The Schedule TO, amends and supplements (1) the Reporting
Persons' Tender Offer Statement on Schedule TO filed on September 4, 2002 (the
"Initial Schedule TO") and (2) the Reporting Persons' Statement on Schedule 13D,
as amended and relates to the offer by Unocal to exchange 0.6527 of a share of
Unocal common stock (including the associated preferred stock purchase rights)
for each outstanding share of Pure Resources, Inc. common stock, on the terms
and conditions contained in Unocal's prospectus, dated September 4, 2002, as
amended, and in the related letter of transmittal, copies of which are
incorporated by reference to Exhibit (a)(1), as amended, and Exhibit (a)(2) to
the Initial Schedule TO (which, together with any amendments or supplements
thereto, collectively constitute the "Offer").

ITEM 12.    EXHIBITS.
--------    ---------

(a)(13)     Press Release of Unocal dated October 1, 2002, announcing an
            injunction relating to the Offer (incorporated by reference to Form
            425 filed by Unocal on October 1, 2002).







                                    SIGNATURE

            After due inquiry and to the best of my knowledge and belief, I
certify that the information set forth in this statement is true, complete and
correct.

                                    Union Oil Company of California



                                    By  /s/ Douglas M. Miller
                                      ----------------------------------
                                       Name: Douglas M. Miller
                                       Title: Vice President, Corporate
                                              Development



                                    Unocal Corporation



                                    By  /s/ Douglas M. Miller
                                      ----------------------------------
                                       Name: Douglas M. Miller
                                       Title: Vice President, Corporate
                                              Development





Dated:  October 1, 2002






                                  EXHIBIT INDEX



 (a)(13)    Press Release of Unocal Corporation dated October 1, 2002,
            announcing an injunction relating to the Offer (incorporated by
            reference to Form 425 filed by Unocal on October 1, 2002).