EXHIBIT 8.1

                       [LETTERHEAD OF LATHAM & WATKINS]

                                 July 15, 2002

Amgen Inc.
One Amgen Center Drive
Thousand Oaks, California  91320

     Re: Amended and Restated Agreement and Plan of Merger by and among Amgen
Inc., AMS Acquisition Inc. and Immunex Corporation dated as of December 16,
2001, as amended by the First Amendment to the Amended and Restated Agreement
and Plan of Merger, dated as of July 15, 2002

Ladies and Gentlemen:

     We have acted as counsel to Amgen Inc., a Delaware corporation ("Parent"),
in connection with the proposed merger (the "Merger") of Immunex Corporation, a
Washington corporation (the "Company"), with and into AMS Acquisition Inc., a
Washington corporation and a direct, wholly owned subsidiary of Parent ("Merger
Sub"), pursuant to an Amended and Restated Agreement and Plan of Merger Among
Parent, Merger Sub and the Company dated as of December 16, 2001, as amended by
the First Amendment to the Amended and Restated Agreement and Plan of Merger,
dated as of July 15, 2002 (the "Merger Agreement"). Capitalized terms not
defined herein have the meanings specified in the Merger Agreement.

     In acting as counsel to Parent in connection with the Merger, we have
participated in the preparation of the Merger Agreement, and pursuant to Section
7.2(c) of the Merger Agreement, you have requested our opinion regarding
whether, on the basis of the facts and assumptions set forth herein, the Merger
will be treated for United States federal income tax purposes as a
reorganization within the meaning of Section 368(a) of the Internal Revenue Code
of 1986, as amended (the "Code"). In rendering our opinion, we have examined
and, with your consent, are expressly relying upon (without any independent
investigation or review thereof) the truth and accuracy of the statements,
covenants, representations and warranties contained in (i) the Merger Agreement
(including any Exhibits, Annexes and Schedules thereto), (ii) the Joint
Proxy/Prospectus; (iii) representations made to us by Parent and the Company in
their respective letters provided to us, each dated the date hereof (the
"Representation Letters"), and (iv) such other documents and corporate records
as we have deemed necessary or appropriate for purposes of our opinion.


July 15, 2002
Page 2

     In addition, we have assumed, with your consent, that:

     1.   Original documents (including signatures) are valid and authentic,
          documents submitted to us as copies conform to the original documents,
          and there has been (or will be by the Effective Time of the Merger)
          due execution and delivery of all documents where due execution and
          delivery are prerequisites to effectiveness thereof;

     2.   The Merger will be consummated in the manner contemplated by, and in
          accordance with the provisions of, the Merger Agreement and the Joint
          Proxy/Prospectus, and will be effective under the laws of the State of
          Washington;

     3.   All statements, descriptions and representations contained in any of
          the documents referred to herein or otherwise made to us are true,
          complete and correct, and no actions have been taken or will be taken
          which are inconsistent with such statements, descriptions or
          representations or which make any such statements, descriptions or
          representations untrue, incomplete or incorrect at the Effective Time;

     4.   Any statements made in any of the documents referred to herein "to the
          knowledge of" or similarly qualified are true, complete and correct
          and will continue to be true, complete and correct at all times up to
          and including the Effective Time, in each case without such
          qualification; and

     5.   The parties have complied with and, if applicable, will continue to
          comply with, the covenants contained in the Merger Agreement and the
          Joint Proxy/Prospectus.

     Based upon the foregoing, and subject to the qualifications and limitations
stated herein, we are of the opinion that the Merger will be treated for United
States federal income tax purposes as a reorganization within the meaning of
Section 368(a) of the Code.

     In addition to the matters set forth above, this opinion is subject to the
exceptions, limitations and qualifications set forth below.

     1.   This opinion represents our best judgment, as of the date hereof,
          regarding the application of United States federal income tax laws
          arising under the Code, existing judicial decisions, administrative
          regulations and published rulings and procedures, but does not address
          all of the United States federal income tax consequences of the
          Merger. We express no opinion as to United States federal, state,
          local, foreign, or other tax consequences, other than as set forth
          herein. Our opinion is not binding upon the Internal Revenue Service
          or the courts, and there is no assurance that the Internal Revenue
          Service will not assert a contrary position. Furthermore, no assurance
          can be given that future legislative, judicial


July 15, 2002
Page 3

          or administrative changes, on either a prospective or retroactive
          basis, would not adversely affect the accuracy of the conclusions
          stated herein. Nevertheless, we undertake no responsibility to advise
          you of any new developments in the application or interpretation of
          the United States federal income tax laws.

     2.   No opinion is expressed as to any transaction other than the Merger as
          described in the Merger Agreement or to any transaction whatsoever,
          including the Merger, if, to the extent relevant to our opinion,
          either all the transactions described in the Merger Agreement are not
          consummated in accordance with the terms of the Merger Agreement and
          without waiver or breach of any provisions thereof, or all of the
          representations, warranties, statements and assumptions upon which we
          have relied are not true and accurate at all relevant times.

     This opinion is rendered to you in connection with the Merger and pursuant
to the requirements of Section 7.2(c) of the Merger Agreement and is not to be
used, circulated, quoted or otherwise referred to or relied upon for any other
purpose without our express written permission. In addition, this opinion letter
may not be relied upon by or furnished to any other person, firm, corporation or
entity without our prior written consent.

                                Very truly yours,

                                /s/ Latham & Watkins