EXHIBIT 8.1

                       [SHEARMAN & STERLING LETTERHEAD]

                                 May 22, 2002

Amgen Inc.
One Amgen Center Drive
Thousand Oaks, CA 91320-1799

                    Liquid Yield Option(TM) Notes Due 2032

Ladies and Gentlemen:

      We have acted as special tax counsel for Amgen Inc. (the "Company") in
connection with the preparation and filing of a Registration Statement on Form
S-3 (the "Registration Statement") pursuant to the Securities Act of 1933, as
amended (the "Securities Act"), relating to the registration for resale under
the Securities Act of $2,821,208,500 aggregate issue price of the Company's
Liquid Yield Option(TM) Notes due 2032 (the "LYONs") which may be converted in
certain cases into shares of the Company's common stock. The LYONs were issued
under an Indenture, dated as of March 1, 2002 (the "Indenture"), between the
Company and LaSalle Bank National Association, as indenture trustee.

      In preparing this opinion, we have examined and relied on such documents
as we have deemed appropriate, including INTER ALIA, the Registration
Statement, the Indenture, and the originals or copies, certified or otherwise
identified to our satisfaction, of all such corporate records of the Company
and such other instruments, certificates and other documents of public
officials and such other persons, and we have made such investigations of law
as we have deemed appropriate as a basis for the opinion expressed below.

      Based on (i) the foregoing; (ii) a sensitivity analysis prepared by
Merrill Lynch, Pierce, Fenner & Smith Incorporated ("MLPF&S") showing that,
under reasonable assumptions regarding future growth rates in the market
trading price of the LYONs, the dividend yield on the Company's common stock
and other relevant factors, contingent interest would become payable over the
term of the LYONs; and (iii) on certain estimates made by MLPF&S regarding the
present value of these contingent interest payments, we are of the opinion that:

      1.  the LYONs will be treated as indebtedness for United States federal
income tax purposes;

      2.  the LYONs will be subject to the regulations governing contingent
payment debt instruments contained in section 1.1275-4(b) of the Treasury
Regulations; and

      3.  the term "comparable yield" means the annual yield the Company would
pay, as of the initial issue date, on a fixed-rate, nonconvertible debt
security, with no contingent payments, but with terms and conditions otherwise
comparable to those of the LYONs.

Depending on the identity of the persons to whom the LYONs were marketed or
sold, there may be a presumption that the comparable yield is the applicable
federal rate based on the overall maturity of the LYONs. This presumption may
only be overcome with clear and convincing evidence that the comparable yield
should be some yield other than the applicable federal rate.

      We confirm that the statements in the Registration Statement under the
captions "Summary--The Offering--Tax Original Issue Discount" and "Certain
United States Federal Income Tax Considerations," insofar as such statements
constitute a summary of the legal matters referred to therein, have been
reviewed by us and are correct in all material respects.
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(TM) Trademark of Merrill Lynch & Co., Inc.



Amgen Inc.                                                         May 22, 2002
                                      2


      We express no opinions other than those expressed herein. We hereby
consent to the filing of this opinion as an exhibit to the Registration
Statement and to the use of our name under the heading "Legal Matters" in the
Registration Statement. In giving this consent, we do not thereby admit that we
are included in the category of persons whose consent is required under Section
7 of the Securities Act or the rules and regulations promulgated thereunder.

                                          Very truly yours,

                                          /s/  SHEARMAN & STERLING