UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D. C. 20549


                                    FORM 11-K


                 Annual Report Pursuant to Section 15(d) of the
                         Securities Exchange Act of 1934



(Mark One)

[X]        Annual report pursuant to Section 15(d) of the Securities Exchange
           Act of 1934

                   For the fiscal year ended December 31, 2001


                                       Or


[  ]       Transition report pursuant to Section 15(d) of the Securities
           Exchange Act of 1934
           For the transition period from              to
                                          ------------    --------------

           Commission file number   1-8483


A. Full title of the plan and the address of the plan, if different from that of
the issuer named below:


                 MOLYCORP, INC. 401(K) RETIREMENT SAVINGS PLAN



B. Name of issuer of the securities held pursuant to the Plan and the address of
its principal executive office:

                               Unocal Corporation,
           2141 Rosecrans Avenue, Suite 4000, El Segundo, California 90245




                  MOLYCORP, INC. 401(k) RETIREMENT SAVINGS PLAN
                          INDEX TO FINANCIAL STATEMENTS



The following financial statements reflect the status of the Molycorp, Inc.
401(k) Retirement Savings Plan as of December 31, 2001 and 2000, and the results
of its transactions for each of the years then ended.


                                                                    Page Number



Report of Independent Accountants                                            1

Financial Statements:

     Statements of Net Assets Available for Benefits
        at December 31, 2001 and 2000                                        2

     Statements of Changes in Net Assets Available for Benefits
        for the years ended December 31, 2001 and 2000                       2

     Notes to Financial Statements                                          3-6

Supplemental Schedules*:

     Schedule of Assets Held for Investment Purposes
        at December 31, 2001                                                 8

Exhibit Index                                                                9



* Supplemental schedules required by the Employee Retirement Income Security Act
of 1974  that are  omitted  are not  applicable  to the  Molycorp,  Inc.  401(k)
Retirement Savings Plan.




                        REPORT OF INDEPENDENT ACCOUNTANTS




To the Administrative  Committee of the Molycorp, Inc. 401(k) Retirement Savings
Plan:



         In our opinion, the accompanying statements of net assets available for
benefits and the related statements of changes in net assets available for
benefits present fairly, in all material respects, the net assets available for
benefits of the Molycorp, Inc. 401(k) Retirement Savings Plan (the "Plan") at
December 31, 2001 and 2000, and the changes in net assets available for benefits
for the years then ended in conformity with accounting principles generally
accepted in the United States of America. These financial statements are the
responsibility of the Plan's management; our responsibility is to express an
opinion on these financial statements based on our audits. We conducted our
audits of these statements in accordance with auditing standards generally
accepted in the United States of America which require that we plan and perform
the audits to obtain reasonable assurance about whether the financial statements
are free of material misstatement. An audit includes examining, on a test basis,
evidence supporting the amounts and disclosures in the financial statements,
assessing the accounting principles used and significant estimates made by
management, and evaluating the overall financial statement presentation. We
believe that our audits provide a reasonable basis for our opinion.



        Our audits were conducted for the purpose of forming an opinion on the
basic financial statements taken as a whole. The supplemental schedule of assets
held for investment purposes at December 31, 2001 is presented for the purpose
of additional analysis and is not a required part of the basic financial
statements but is supplementary information required by the Department of
Labor's Rules and Regulations for Reporting and Disclosure under the Employee
Retirement Income Security Act of 1974. This supplemental schedule is the
responsibility of the Plan's management. The supplemental schedule has been
subjected to the auditing procedures applied in the audits of the basic
financial statements and, in our opinion, is fairly stated in all material
respects in relation to the basic financial statements taken as a whole.







/s/ PricewaterhouseCoopers LLP

PricewaterhouseCoopers LLP
Los Angeles, California
May 24, 2002

                                      -1-


                  Molycorp, Inc. 401(k) Retirement Savings Plan
                 Statements of Net Assets Available for Benefits

                                                             December 31,
                                                      2001                2000
--------------------------------------------------------------------------------

Investments at fair value                          $142,670            $128,303

                                              --------------     ---------------
Net assets available for benefits                  $142,670            $128,303
                                              ==============     ===============


                  Molycorp, Inc. 401(k) Retirement Savings Plan
           Statements of Changes in Net Assets Available for Benefits

                                                       Year Ended December 31,
                                                         2001              2000
--------------------------------------------------------------------------------

Additions:
  Additions to (deductions from) net assets attributed to:
    Investment income (loss)
      Net depreciation in fair value of investments    (10,505)        $ (8,110)
      Interest                                           3,604            3,953
      Dividends                                            230              118
                                                      ----------       ---------
        Total investment loss                           (6,671)          (4,039)

    Participant contributions                           37,347           36,263
                                                      ----------       ---------

        Total additions                                 30,676           32,224
                                                      ----------       ---------

Deductions:
    Participant withdrawals & distributions             16,309            6,288
                                                      ----------       ---------

        Total deductions                                16,309            6,288
                                                      ----------       ---------

    Net increase                                        14,367           25,936
                                                      ----------       ---------

Net assets available for benefits:
    Beginning of year                                  128,303          102,367
                                                      ----------       ---------
    End of year                                       $142,670         $128,303
                                                      ==========       =========

                 See accompanying notes to financial statements.

                                      -2-



                          NOTES TO FINANCIAL STATEMENTS

NOTE 1 - DESCRIPTION OF THE PLAN

General

        The Molycorp, Inc. 401(k) Retirement Savings Plan (the "Plan") is
sponsored by Molycorp, Inc. (the "Company"), an indirect wholly owned subsidiary
of Unocal Corporation. The Plan provides for voluntary pre-tax contributions by
participants, who are employees represented by collective bargaining agents at
certain facilities operated by the Company. The Plan's trustee and administrator
is Putnam Fiduciary Trust Company (the "Trustee"). Each participant is allowed
to choose how funds are invested from a range of investment fund options made
available through Putnam investments and Unocal Corporation common stock. The
Plan is subject to certain provisions of the Employee Retirement Income Security
Act of 1974 ("ERISA") as a defined contribution plan.

        The Plan booklet dated December 1, 1996 constitutes part of a prospectus
covering securities that have been registered under the Securities Act of 1933.
The December 1, 1996 booklet can be referenced for other information about the
Plan.

        A restated Plan document dated September 1, 2001, was adopted in late
2001 to document modifications subsequent to the January 1, 2001 Plan document.

Participation

        Collective bargaining unit employees at the Company's Questa and York
facilities became eligible to participate in the Plan as of January 1, 1991 if
at least six months of service were completed prior to January 1, 1991.
Otherwise, participants become eligible to participate in the Plan upon
completion of six months of service.

Contributions

        Voluntary participant contributions to the Plan are made on a pre-tax
basis and cannot exceed 15 percent of a participant's base pay. The pre-tax
contributions are also known as 401(k) contributions. Contributions cannot
exceed the amount prescribed by law and cannot be calculated on an amount of
base pay in excess of the amount allowed by law. The Plan does not allow for
employer contributions.

Participant Accounts

        Each participant's account is credited with the participant's
contributions and increased or decreased by the respective investment earnings
or losses of the individual investments as governed by the participant's
investment selections.

Vesting

        Participants are always 100 percent vested in participant contributions
and in the dividends and interest on those contributions.

                                      -3-



Payment of Benefits

        On termination of employment or at such time that participants become
eligible to receive benefits, participants may elect to receive their account
balances or defer their distributions until a later date, but no later than 60
days after the end of the plan year in which the latest of the following occurs:
April 1 after the close of the calendar year in which the participant attains
age 70 1/2, or two years after the participant's employment terminates. If a
participant continues to work after age 70 1/2, distribution of a portion of the
participant's account balance is required by April 1 of the calendar year
following the calendar year in which the participant attains age 70 1/2.

Federal Income Tax Status

        In June 2002, the Company received a ruling, from the Internal Revenue
Service, that subject to the adoption of certain technical amendments, the Plan
meets the requirements of Section 401(a) of the Internal Revenue Code (the
"Code") of 1986, as amended, and that the Trust established thereunder is
entitled to exemption under the provisions of the Code; therefore, the Plan is
not required to pay any federal income taxes. Contributions to and earnings on
Plan accounts will not be taxable to participants prior to withdrawal from the
Plan.

Withdrawals from the Plan are generally subject to federal income tax. Also,
in-service withdrawals and withdrawals following termination of employment prior
to retirement may be subject to an additional 10 percent federal penalty tax.

Plan Termination

        The Company expects to continue the Plan indefinitely, but, as future
conditions cannot be foreseen, the Company may at any time or from time to time
amend or terminate the Plan in whole or in part, subject to the requirements of
ERISA and other applicable laws. An amendment may affect present, as well as
future participants, but may not diminish the account of any participant
existing on the effective date of such amendment. The Company has no present
intent to terminate the Plan.

NOTE 2 - Summary of Significant Accounting Policies

Basis of Accounting

        The accompanying financial statements are prepared on the accrual basis
of accounting in conformity with accounting principles generally accepted in the
United States of America. In addition, the following accounting policies are
applied:

       a.  Purchases and sales of securities are recorded on a trade-date basis.

       b.  Dividends are recorded on an ex-dividend date basis.

       c.  Interest income is recorded on the accrual basis.

       d.  Benefits are recorded when paid.

        The Plan presents in the statements of changes in net assets available
for benefits the net appreciation (depreciation) in the fair value of its
investments which consist of the realized gains or losses and the unrealized
appreciation (depreciation) on those investments.

                                      -4-


Valuation of Investments

       The Plan's investments are stated at fair value. Shares of registered
investment companies are valued at the net asset value of shares held by the
Plan at year-end. Shares of Unocal common stock are valued at the closing price
as reported for the New York Stock Exchange Composite Transactions at December
31, 2001 and 2000. Investments in common trust funds are valued based on
information provided by the Plan's investment custodian. The financial
statements of the common trust funds are audited annually by independent
accountants.

Use of Estimates in Preparation of the Financial Statements

        The preparation of financial statements in conformity with accounting
principles generally accepted in the United States of America requires the
Plan's management to make estimates and assumptions that affect the reported
amounts of assets and liabilities and disclosure of contingent assets and
liabilities at the dates of the financial statements and the reported amounts of
additions to and deductions from net assets during the reporting periods. Actual
results could differ from those estimates.

NOTE 3 - Investments

    The following investments represent 5 percent or more of the Plan's net
assets:
                                                         December 31,
                                                      2001          2000
------------------------------------------------------------------------------

Putnam Money Market Fund
97,114 and 75,501 shares, respectively                 $ 97,114      $ 75,501

Putnam New Opportunities Fund
418 and 330 shares, respectively                         17,528        19,773

Putnam S&P 500 Index Fund
363 and 484 shares, respectively                         10,109        15,320

Putnam International Growth Fund
487 and 361 shares, respectively                          9,718         8,952

Unocal Common Stock
21 and 153 shares, respectively                             744         5,903

The Plan's investments appreciated (depreciated) in value as follows:

                                                December 31,
                                           2001             2000
                                        -----------------------------
Mutual funds                               ($8,804)         ($7,915)
Common or collective trust                    (902)            (975)
Common stock                                  (799)              780
                                        ------------    -------------
                                          ($10,505)         ($8,110)
                                        ============    =============

                                      -5-




NOTE 4 - Parties-in-interest

    Certain of the Plan's investments are shares of mutual funds managed by the
Trustee, as defined by the Plan Agreement. Therefore, these transactions qualify
as party-in-interest transactions for which a statutory exemption exists.

    Unocal Corporation, which also qualifies as a party-in-interest, absorbs
substantially all of the administrative expenses of the Plan, which were nominal
for the years ended December 31, 2001 and 2000. Such transactions with the
Company qualify for a statutory exemption.

                                      -6-




                                    SIGNATURE


Pursuant to the requirements of the Securities Exchange Act of 1934, the
Committee appointed by the Board of Directors of the Company to administer the
Plan has duly caused this annual report to be signed on its behalf by the
undersigned hereunto duly authorized.


                                   MOLYCORP, INC. 401(k) RETIREMENT SAVINGS PLAN






Date:  June 28, 2002                       By: /s/ Roger T. Inabu
                                              ----------------------------------
                                               Roger T. Inabu
                                               Comptroller, Molycorp, Inc.

                                      -7-





                  Molycorp, Inc. 401(k) Retirement Savings Plan
                 Schedule of Assets Held for Investment Purposes
                              At December 31, 2001

     (a)                 (b)                                    (c)                              (d)               (e)
              Identity of Issuer,                   Description of Investment,
              Borrower, Lessor                   Including Maturity Date, Rate of
              or Similar Party             Interest, Collateral, Par, or Maturity Value         Cost          Current Value
------------------------------------------------------------------------------------------------------------------------------

                                                                                                                     
      *       Unocal Corporation        Unocal Corporation Common Stock                                                 $ 744
                                        21 shares

     **       Putnam Investments        Putnam Money Market Fund                                                       97,114
                                        97,114 shares

     **       Putnam Investments        Putnam New Opportunities Mutual Fund                                           17,528
                                        418 shares

     **       Putnam Investments        Putnam S&P 500 Index Fund                                                      10,109
                                        363 shares

     **       Putnam Investments        Putnam International Growth Fund                                                9,718
                                        487 shares

     **       Putnam Investments        The Putnam Bond Index Fund                                                      4,190
                                        352 shares

     **       Putnam Investments        Putnam Voyager Fund                                                             1,450
                                        82 shares

     **       Vanguard Group            The Vanguard Windsor II Fund                                                      467
                                        18 shares

     **       Putnam Investments        George Putnam Fund of Boston                                                    1,350
                                        80 shares

                                                                                                            ------------------
                                        Total assets held for investment purposes                                   $ 142,670
                                                                                                            ==================

*   Parent of the Sponsor and employer and, therefore, a party-in-interest for which a statuory exemption exists.
**  Trustee for the Plan and, therefore, a party-in-interest for which a statuory exemption exists.
     The Vanguard Windsor II Fund is also available through Putnam Investments.


                                      -8-



                               UNOCAL CORPORATION

                                  EXHIBIT INDEX





 Exhibit 23      Consent of PricewaterhouseCoopers LLP

                                      -9-