SECURITIES AND EXCHANGE COMMISSION

SCHEDULE TO

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

AMGEN INC.

AMGEN INC.

Liquid Yield Option Notes due 2032 (Zero Coupon—Senior)
(Title of Class of Securities)

031162 AC4 and 031162 AE0
(CUSIP Number of Class of Securities)

CALCULATION OF FILING FEE

Check the appropriate boxes to designate any transactions to which this statement relates:

Check the following box if the filing is a final amendment reporting the results of the tender offer: o

INTRODUCTORY STATEMENT

     As required by, pursuant to the terms of and subject to the conditions set forth in the Indenture, dated as of March 1, 2002 (the “Indenture”), between Amgen Inc., a Delaware corporation (the “Company”), and LaSalle Bank National Association, as trustee (the “Trustee”), for the Company’s Liquid Yield Option Notes due 2032 (Zero Coupon—Senior) (the “Securities”), this Tender Offer Statement on Schedule TO-I (“Schedule TO-I”) is filed by the Company, with respect to the right of each holder (the “Holder”) of the Securities to sell and the obligation of the Company to purchase the Securities, the Company Notice, dated January 31, 2005 (the “Company Notice”), and the related notice materials filed as exhibits to this Schedule TO-I (which Company Notice and related notice materials, as amended or supplemented from time to time, collectively constitute the “Put Option”).

     This Schedule TO-I is intended to satisfy the disclosure requirements of Rule 13e-4(c)(2) under the Securities Exchange Act of 1934, as amended.

Items 1 through 9.

     The Company is the issuer of the Securities and is obligated to purchase all of the Securities if tendered by the holders under the terms and subject to the conditions set forth in the Put Option. The Securities are convertible into shares of common stock, $0.0001 par value per share, of the Company. The Company maintains its registered and principal executive offices at One Amgen Center Drive, Thousand Oaks, California 91320-1799 and the telephone number there is (805) 447-1000. As permitted by General Instruction F to Schedule TO, all of the information set forth in the Put Option is incorporated by reference into this Schedule TO-I.

Item 10. Financial Statements.

     (a) Pursuant to Instruction 2 to Item 10 of Schedule TO, the Company’s financial condition is not material to a holder’s decision whether to put the Securities to the Company because (i) the consideration being paid to holders surrendering Securities consists solely of cash, (ii) the Put Option is not subject to any financing conditions, (iii) the Put Option applies to all outstanding Securities and (iv) the Company is a public reporting company that files reports electronically on EDGAR. The financial condition and results of operations of the Company and its subsidiaries are reported electronically on EDGAR on a consolidated basis.

     (b) Not applicable.

Item 11. Additional Information.

     (a) Not applicable.

     (b) Not applicable.

Item 12. Exhibits.

Item 13. Information Required by Schedule 13E-3.

     Not applicable.

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.

EXHIBIT INDEX

Exhibit 99(a)(1)(A)

COMPANY NOTICE
TO HOLDERS OF

LIQUID YIELD OPTION NOTES DUE 2032
(Zero Coupon—Senior)

ISSUED BY
AMGEN INC.
CUSIP Numbers: 031162 AC4 and 031162 AE0

     NOTICE IS HEREBY GIVEN pursuant to the terms and conditions of the Indenture, dated as of March 1, 2002 (the “Indenture”), between Amgen Inc., a Delaware corporation (the “Company”), and LaSalle Bank National Association, as trustee and paying agent (the “Paying Agent”), and the Liquid Yield Option Notes Due 2032 (Zero Coupon—Senior) (the “Securities”) of the Company, that at the option of each holder (the “Holder”) of the Securities, the Securities will be purchased by the Company for $738.68 in cash per $1,000 principal amount at maturity of the Securities (the “Purchase Price”), subject to the terms and conditions of the Indenture, the Securities and this Company Notice and related notice materials, as amended and supplemented from time to time (the “Put Option”). Holders may surrender their Securities from January 31, 2005 through 5:00 p.m., New York City time, on Tuesday, March 1, 2005 (the “Purchase Date”). This Company Notice is being sent pursuant to the provisions of Section 3.08 of the Indenture and paragraph 7 of the Securities. All capitalized terms used but not specifically defined in this Company Notice shall have the meanings given to such terms in the Indenture and the Securities.

     To exercise your option to have the Company purchase the Securities and receive payment of $738.68 per $1,000 principal amount at maturity of the Securities, you must validly surrender the Securities prior to 5:00 p.m., New York City time, on the Purchase Date. Securities surrendered for purchase may be withdrawn at any time prior to 5:00 p.m., New York City time, on the Purchase Date. The right of Holders to surrender Securities for purchase in the Put Option expires at 5:00 p.m., New York City time, on the Purchase Date.

     The Trustee has informed the Company that, as of the date of this Company Notice, all custodians and beneficial holders of the Securities hold the Securities through Depository Trust Company (“DTC”) accounts and that there are no certificated Securities in non-global form. Accordingly, all Securities surrendered for purchase hereunder must be delivered through the transmittal procedures of DTC.

The Paying Agent is:
LaSalle Bank National Association

     Additional copies of this Company Notice may be obtained from the Paying Agent at its addresses set forth above.

TABLE OF CONTENTS

     No person has been authorized to give any information or to make any representations other than those contained in the Put Option and, if given or made, such information or representations must not be relied upon as having been authorized. The Put Option does not constitute an offer to buy or the solicitation of an offer to sell securities in any circumstances or jurisdiction in which such offer or solicitation is unlawful. The delivery of the Put Option shall not under any circumstances create any implication that the information contained in the Put Option is current as of any time subsequent to the date of such information. None of the Company or its board of directors or employees are making any representation or recommendation to any Holder as to whether or not to surrender such Holder’s Securities. You should consult your own financial and tax advisors and must make your own decision as to whether to surrender your Securities for purchase and, if so, the amount of Securities to surrender.

i

SUMMARY TERM SHEET

     The following are answers to some of the questions that you may have about the Put Option. To understand the Put Option fully and for a more complete description of the terms of the Put Option, we urge you to read carefully the remainder of this Company Notice because the information in this summary is not complete. We have included page references to direct you to a more complete description of the topics in this summary.

     Who is offering to purchase my securities?

     Amgen Inc., a Delaware corporation (the “Company”), is obligated, at your option, to purchase your validly surrendered Liquid Yield Option Notes due 2032 (Zero Coupon—Senior) (the “Securities”). (Page 3)

     Why is the Company offering to purchase my securities?

     The right of each holder (the “Holder”) of the Securities to sell and the obligation of the Company to purchase the Securities pursuant to the Put Option is a term of the Securities and has been a right of Holders from the time the Securities were issued on March 1, 2002. We are required to repurchase the Securities of any Holder exercising the Put Option pursuant to the terms of the Securities and the Indenture. (Page 4)

     What securities are you obligated to purchase?

     We are obligated to purchase all of the Securities surrendered, at the option of the Holder. As of January 31, 2005, there was $3,949,575,000 aggregate principal amount at maturity of Securities outstanding. The Securities were issued under an Indenture, dated as of March 1, 2002 (the “Indenture”), between the Company and LaSalle Bank National Association, as trustee and paying agent (the “Paying Agent”). (Page 4)

     How much will you pay and what is the form of payment?

     Pursuant to the terms of the Indenture and the Securities, we will pay, in cash, a purchase price of $738.68 per $1,000 principal amount at maturity of the Securities (the “Purchase Price”) with respect to any and all Securities validly surrendered for purchase and not withdrawn. The Purchase Price is based solely on the requirements of the Indenture and the Securities and bears no relationship to the market price of the Securities or the Common Stock. (Page 4)

     How can I determine the market value of the Securities?

     There is no established reporting system or market for trading in the Securities. To the extent that the Securities are traded, prices of the Securities may fluctuate widely depending on trading volume, the balance between buy and sell orders, prevailing interest rates, the Company’s operating results, the trading price of the Company’s common stock and the market for similar securities. To the extent available, Holders are urged to obtain current market quotations for the Securities prior to making any decision with respect to the Put Option. The common stock, $0.0001 par value per share (the “Common Stock”), of the Company into which the Securities are convertible is listed on the Nasdaq National Market (“NASDAQ”) under the symbol “AMGN.” On January 24, 2005, the last reported sales price of the Common Stock on the NASDAQ was $62.12 per share. (Pages 4-5)

     What does the board of directors of the Company think of the Put Option?

     The board of directors of the Company has not made any recommendation as to whether you should surrender your Securities for purchase in the Put Option. You must make your own decision whether to

1

surrender your Securities for purchase in the Put Option and, if so, the amount of Securities to surrender. (Page 4)

     When does the Put Option expire?

     The Put Option expires at 5:00 p.m., New York City time, on Tuesday, March 1, 2005 (the “Purchase Date”). We will not extend the period Holders have to accept the Put Option unless required to do so by the Federal securities laws. (Page 4)

     What are the conditions to the purchase by the Company of the Securities?

     The purchase by us of validly surrendered Securities is not subject to any condition other than such purchase being lawful.

     How do I surrender my Securities?

     To surrender your Securities for purchase pursuant to the Put Option, you must surrender the Securities through the transmittal procedures of the Depository Trust Company (“DTC”) no later than 5:00 p.m., New York City time, on the Purchase Date.

     By surrendering your Securities through the transmittal procedures of DTC, you agree to be bound by the terms of the Put Option set forth this Company Notice (Pages 6-7)

     If I surrender my Securities, when will I receive payment for them?

     We will accept for payment all validly surrendered Securities promptly upon expiration of the Put Option. We will promptly forward to the Paying Agent, prior to 10:00 a.m., New York City time, on March 2, 2005, the appropriate amount of cash required to pay the Purchase Price for the surrendered Securities, and the Paying Agent will promptly distribute the cash to the DTC, the sole record Holder. The DTC will thereafter distribute the cash to its participants in accordance with its procedures. (Page 8)

     Until what time can I withdraw previously surrendered Securities?

     You can withdraw Securities previously surrendered for purchase at any time until 5:00 p.m., New York City time, on the Purchase Date. (Page 8)

     How do I withdraw previously surrendered Securities?

     To withdraw previously surrendered Securities, you must comply with the withdrawal procedures of the DTC prior to 5:00 p.m., New York City time, on the Purchase Date. (Page 8)

     Do I need to do anything if I do not wish to surrender my Securities for purchase?

     No. If you do not surrender your Securities before the expiration of the Put Option, we will not purchase your Securities and such Securities will remain outstanding subject to their existing terms. (Pages 4-5)

2

     If I choose to surrender my Securities for purchase, do I have to surrender all of my Securities?

     No. You may surrender all of your Securities, a portion of your Securities or none of your Securities for purchase. If you wish to surrender a portion of your Securities for purchase, however, you must surrender your Securities in a principal amount at maturity of $1,000 or an integral multiple thereof. (Page 4)

     If I do not surrender my Securities for purchase, will I continue to be able to exercise my conversion rights?

     Yes. If you do not surrender your Securities for purchase, your conversion rights will not be affected. You will continue to have the right to convert each $1,000 principal amount at maturity of a Security into 8.8601 shares of Common Stock, subject to the terms, conditions and adjustments specified in the Indenture and the Securities. (Page 4)

     If I am a U.S. resident for U.S. federal income tax purposes, will I have to pay taxes if I surrender my Securities for purchase in the Put Option?

     The receipt of cash in exchange for Securities pursuant to the Put Option will be a taxable transaction for U.S. federal income tax purposes and you may recognize gain, income, loss or deduction. You should consult with your tax advisor regarding the actual tax consequences to you. (Pages 10-13)

     Who is the Paying Agent?

     LaSalle Bank National Association, the trustee under the Indenture, is serving as Paying Agent in connection with the Put Option. Its address and telephone number are set forth on the front cover page of this Company Notice.

     Who can I talk to if I have questions about the Put Option?

     Questions and requests for assistance in connection with the surrender of Securities for purchase in the Put Option may be directed to the Paying Agent at the address and telephone and facsimile numbers set forth on the cover of this Company Notice.

IMPORTANT INFORMATION CONCERNING THE OPTION

     1. Information Concerning the Company. Amgen Inc., a Delaware corporation (the “Company”), is obligated to purchase the Liquid Yield Option Notes Due 2032 (Zero Coupon—Senior) (the “Securities”). The Securities are convertible into the common stock, $0.0001 par value per share (the “Common Stock”), of the Company, subject to the terms, conditions and adjustments specified in the Indenture and the Securities.

     The Company is a global biotechnology company that discovers, develops, manufactures and markets human therapeutics based on advances in cellular and molecular biology. The Company was incorporated in California in 1980 and merged into a Delaware corporation in 1987. The Company maintains its registered and principal executive offices at One Amgen Center Drive, Thousand Oaks, California 91320-1799 and the telephone number there is (805) 447-1000.

3

     2. Information Concerning The Securities. The Securities were issued under an Indenture, dated as of March 1, 2002 (the “Indenture”), between the Company and LaSalle Bank National Association, as trustee and paying agent (the “Paying Agent”). The Securities mature on March 1, 2032.

     2.1. The Company’s Obligation to Purchase the Securities. Pursuant to the terms of the Securities and the Indenture, the Company is obligated to purchase all Securities validly surrendered for purchase and not withdrawn, at the Holder’s option, on March 1, 2005. This Put Option will expire at 5:00 p.m., New York City time, on Tuesday, March 1, 2005 (the “Purchase Date”). We will not extend the period Holders have to accept the Put Option unless required to do so by the Federal securities laws. The purchase by the Company of validly surrendered Securities is not subject to any condition other than such purchase being lawful.

     2.2. Purchase Price. Pursuant to the Securities, the purchase price to be paid by the Company for the Securities on the Purchase Date is $738.68 per $1,000 principal amount at maturity of the Securities (the “Purchase Price”). The Purchase Price will be paid in cash with respect to any and all Securities validly surrendered for purchase and not withdrawn prior to 5:00 p.m., New York City time, on the Purchase Date. Securities surrendered for purchase will be accepted only in principal amounts at maturity equal to $1,000 or integral multiples thereof. The Original Issue Discount (as defined in the Securities) will cease to accrue on the Purchase Date on Securities validly surrendered for purchase and not withdrawn unless the Company defaults in making payment on these Securities.

     The Purchase Price is based solely on the requirements of the Indenture and the Securities and bears no relationship to the market price of the Securities or the Common Stock. Thus, the Purchase Price may be significantly higher or lower than the market price of the Securities on the Purchase Date. Holders of Securities are urged to obtain the best available information as to potential current market prices of the Securities, to the extent available, and the Common Stock before making a decision whether to surrender their Securities for purchase.

     None of the Company or its board of directors or employees are making any recommendation to Holders as to whether to surrender or refrain from surrendering Securities for purchase pursuant to this Company Notice. Each Holder must make such Holder’s own decision whether to surrender such Holder’s Securities for purchase and, if so, the principal amount of Securities to surrender based on such Holder’s assessment of current market value of the Securities and the Common Stock and other relevant factors.

     2.3. Conversion Rights of the Securities. The Securities are convertible into 8.8601 shares of Common Stock per $1,000 principal amount at maturity of the Securities, subject to adjustment under certain circumstances specified in the Indenture. The Paying Agent is currently acting as conversion agent for the Securities.

     Holders that do not surrender their Securities for purchase pursuant to the Put Option will maintain the right to convert their Securities into Common Stock, subject to the terms, conditions and adjustments specified in the Indenture and the Securities. Any Securities which are surrendered pursuant to the Put Option may be converted in accordance with the terms of the Indenture and the Securities only if such surrender has been validly withdrawn prior to 5:00 p.m., New York City time, on the Purchase Date, as described in Section 4 below.

     2.4. Market for the Securities and the Company’s Common Stock. There is no established reporting system or trading market for trading in the Securities. However, we believe the Securities currently are traded over the counter. We believe that there is no practical way to accurately determine the trading history of the Securities. To the extent that the Securities are traded, prices of the Securities may fluctuate widely depending on trading volume, the balance between buy and sell orders, prevailing interest rates, the Company’s operating results, the market price of the Common

4

Stock and the market for similar securities. Following the expiration of the Put Option, we expect that Securities not purchased in the Put Option will continue to be traded over the counter; however, the trading market for the Securities may be even more limited. A debt security with a smaller outstanding principal amount available for trading (a smaller “float”) may command a lower price and trade with greater volatility than would a comparable debt security with a larger float. Consequently, our purchase of a significant amount of the Securities pursuant to the Put Option will reduce the float and may negatively affect the liquidity, market value and price volatility of the Securities that remain outstanding following the Put Option. We cannot assure you that a market will exist for the Securities following the Put Option. The extent of the public market for the Securities following consummation of the Put Option will depend upon, among other things, the remaining outstanding principal amount at maturity of the Securities at such time, the number of holders of Securities remaining at that time and the interest on the part of securities firms in maintaining a market in the Securities. The Paying Agent has informed us that, as of the date of this Company Notice, all of the Securities are held in global form through DTC. As of January 31, 2005, there was $3,949,575,000 aggregate principal amount at maturity of Securities outstanding and DTC was the sole record Holder of the Securities.

     The Common Stock into which the Securities are convertible is listed on the Nasdaq National Market (“NASDAQ”) under the symbol “AMGN.” The following table sets forth, for the fiscal quarters indicated, the high and low closing sales prices of the Common Stock as reported on the NASDAQ.

     On January 24, 2005, the last reported sales price of the Common Stock on the NASDAQ was $62.12 per share. As of January 24, 2005, there were approximately 1,261,283,740 shares of Common Stock outstanding. We urge you to obtain current market information for the Securities, to the extent available, and the Common Stock before making any decision to surrender your Securities pursuant to the Put Option.

5

     2.5. Redemption. Beginning March 1, 2007, the Securities are redeemable for cash at any time at the option of the Company, in whole or in part, at a redemption price equal to the Issue Price (as defined in the Indenture) plus accrued Original Issue Discount (as defined in the Indenture). If the applicable Security has been converted to a semiannual coupon note following the occurrence of a Tax Event (as defined in the Indenture), the redemption price will be equal to the Restated Principal Amount (as defined in the Indenture) plus accrued and unpaid interest from the date of such conversion to but not including the redemption date.

     2.6. Change in Control. A Holder may require the Company to redeem for cash such Holder’s securities if there is a Change in Control (as defined in the Securities) on or prior to March 1, 2007 at a redemption price equal to the Issue Price (as defined in the Securities) plus accrued Original Issue Discount (as defined in the Securities).

     2.7. Ranking. The Securities are unsecured and unsubordinated obligations of the Company and rank equal in right of payment to all of the Company’s existing and future unsecured and unsubordinated indebtedness. However, the Securities are effectively subordinated to all existing and future obligations of the Company’s subsidiaries and to the Company’s obligations that are secured to the extent of the security.

     2.8. Dividends. The Holders of Securities are not entitled to dividends. Upon conversion into Common Stock, the Holders will be entitled to dividends, if any, made to holders of Common Stock.

     3. Procedures To Be Followed By Holders Electing To Surrender Securities For Purchase. Holders will not be entitled to receive the Purchase Price for their Securities unless they validly surrender and do not withdraw the Securities on or before 5:00 p.m., New York City time, on the Purchase Date. Only registered Holders are authorized to surrender their Securities for purchase. Holders may surrender some or all of their Securities; however, any Securities surrendered must be in $1,000 principal amount at maturity or an integral multiple thereof. If Holders do not validly surrender their Securities on or before 5:00 p.m., New York City time, on the Purchase Date, their Securities will remain outstanding subject to the existing terms of the Securities.

     3.1. Method of Delivery. The Trustee has informed the Company that, as of the date of this Company Notice, all custodians and beneficial holders of the Securities hold the Securities through DTC accounts and that there are no certificated Securities in non-global form. Accordingly, all Securities surrendered for purchase hereunder must be delivered through DTC’s Automatic Tenders over the Participant Terminal System (“PTS”). This Company Notice constitutes the Company Notice (as defined in the Indenture) and delivery of Securities via PTS will satisfy the notice requirements of the Indenture. Delivery of Securities and all other required documents, including delivery and acceptance through PTS, is at the election and risk of the person surrendering such Securities.

     3.2. Agreement to be Bound by the Terms of the Put Option. By surrendering your Securities through the transmittal procedures of DTC, a Holder acknowledges and agrees as follows:

6

7

     3.3. Delivery of Securities.

     Securities Held Through a Custodian. A Holder whose Securities are held by a broker, dealer, commercial bank, trust company or other nominee must contact such nominee if such Holder desires to surrender such Holder’s Securities and instruct such nominee to surrender the Securities for purchase on the Holder’s behalf through the transmittal procedures of DTC as set forth below in “- Securities in Global Form” on or prior to 5:00 p.m., New York City time, on the Purchase Date.

     Securities in Global Form. A Holder who is a DTC participant may elect to surrender to the Company such Holder’s beneficial interest in the Securities by:

     In surrendering through PTS, the electronic instructions sent to DTC by the Holder or by a broker, dealer, commercial bank, trust company or other nominee on such Holder’s behalf, and transmitted by DTC to the Paying Agent, will acknowledge, on behalf of DTC and the Holder, receipt by the Holder of and agreement to be bound by the terms of the Put Option, including those set forth above under “- Agreement to be Bound by the Terms of the Put Option.”

8

     4. Right Of Withdrawal. Securities surrendered for purchase may be withdrawn at any time prior to 5:00 p.m., New York City time, on the Purchase Date. In order to withdraw Securities, Holders must comply with the withdrawal procedures of the DTC prior to 5:00 p.m., New York City time, on the Purchase Date. Securities withdrawn from the Put Option may be resurrendered by following the surrender procedures described in Section 3 above.

     5. Payment For Surrendered Securities. We will promptly forward to the Paying Agent, prior to 10:00 a.m., New York City time, on March 2, 2005 the appropriate amount of cash required to pay the Purchase Price for the surrendered Securities, and the Paying Agent will promptly thereafter cause the cash to be distributed to each record Holder that has validly delivered its Securities and not validly withdrawn such delivery prior to 5:00 p.m., New York City time, on the Purchase Date.

     The total amount of funds required by us to purchase all of the Securities is $2,917,472,061 (assuming all of the Securities are validly surrendered for purchase and accepted for payment). In the event any Securities are surrendered and accepted for payment, we intend to use cash from operating cash flow, existing cash balances and/or existing sources of financing to purchase the Securities.

     6. Securities Acquired. Any Securities purchased by us pursuant to the Put Option will be cancelled by the Trustee, pursuant to the terms of the Indenture.

     7. Plans Or Proposals Of The Company. Except as publicly disclosed prior to the date of this Company Notice, the Company does not currently have any plans which would be material to a Holder’s decision to surrender Securities for purchase in the Put Option, which relate to or which would result in:

9

     8. Interests Of Directors, Executive Officers And Affiliates Of The Company In The Securities. Except as otherwise disclosed below, to the knowledge of the Company:

     A list of the directors and executive officers of the Company is attached to this Company Notice as Annex A.

     9. Purchases Of Securities By The Company And Its Affiliates. Each of the Company and its affiliates, including its executive officers and directors, is prohibited under applicable United States federal securities laws from purchasing Securities (or the right to purchase Securities) other than through the Put Option until at least the tenth business day after the Purchase Date. Following such time, if any Securities remain outstanding, the Company and its affiliates may purchase Securities in the open market, in private transactions, through a subsequent tender offer, or otherwise, any of which may be consummated at purchase prices higher or lower than the Purchase Price. Any decision to purchase Securities after the Put Option, if any, will depend upon many factors, including the market price of the Securities, the amount of Securities surrendered for purchase pursuant to the Put Option, the market price of the Common Stock, the business and financial position of the Company and general economic and market conditions.

     10. Material United States Tax Considerations. The following discussion summarizes certain United States federal income tax considerations that may be relevant to a Holder if you exercise the Put Option. This summary is based on the Internal Revenue Code of 1986, as amended (the “Code”), and the regulations, rulings and decisions thereunder, all of which are subject to change, possibly with retroactive effect.

     This summary does not describe all of the tax considerations that may be relevant to you. All Holders are strongly encouraged to consult with their tax advisor about the United States federal, state, local and other tax consequences of exercising the Put Option.

U.S. Holders

     This discussion deals only with U.S. Holders who are beneficial owners of the Securities holding the Securities as capital assets, and does not apply if you are a member of a class of Holders subject to special rules, such as:

10

     You will be a U.S. Holder if you are a beneficial owner of the Securities for U.S. federal income tax purposes and you are:

     If you are not a U.S. Holder, this discussion does not apply to you.

     Generally, your exercise of the Put Option will result in taxable gain or loss to you equal to the difference between (i) the amount of cash received and (ii) your adjusted tax basis in the Securities surrendered. Because you agreed when you purchased your Securities to treat the Securities as subject to the special rules regarding contingent payment debt instruments, your adjusted tax basis in the Securities will generally be equal to your original purchase price for the Securities, increased by any interest income previously accrued by you (determined without regard to any adjustments to interest accruals that arise because projected payments differ from the actual amounts paid), decreased by the amount of any projected payments that have been previously scheduled to be made (without regard to the actual amounts paid) on the Securities, and increased or decreased by the amount of any positive or negative adjustment, respectively, that you are required to make if you purchased your Securities at a price other than the adjusted issue price determined for tax purposes. This gain will generally be treated as ordinary interest income; any loss will be ordinary loss to the extent of interest previously included in income, and thereafter, capital loss (which will be long-term if you held your Securities for more than one year). The deductibility of net capital losses by individuals and corporations is subject to limitations.

     The contingent payment debt instrument regulations are complex. You should consult your tax advisor regarding the accrual of interest, any positive and negative adjustments, and the calculation of adjusted tax basis with respect to your Securities.

11

Non-U.S. Holders

     This discussion describes the tax consequences to a non-U.S. Holder. You are a non-U.S. Holder if you are the beneficial owner of Securities and are, for United States federal income tax purposes:

     If you are a U.S. Holder, this section does not apply to you.

     If you are a non-U.S. Holder, we and other U.S. payers generally will not be required to deduct United States withholding tax from cash received upon exercising the Put Option if:

     Special certification rules apply to non-U.S. Holders that are pass-through entities rather than corporations or individuals. Non-U.S. Holders should consult their tax advisors regarding the certification requirements for such non-U.S. Holders.

     If you cannot satisfy the requirements above, but you are eligible for the benefits of an applicable U.S. income tax treaty that would reduce or eliminate such withholding taxes, you should provide an IRS Form W-8BEN (or successor form) claiming either a partial reduction or complete exemption from such withholding taxes under such treaty. If interest with respect to the Securities is effectively connected with the conduct of a U.S. trade or business by you, you should instead furnish IRS Form W-8ECI.

Backup Withholding

     To prevent backup withholding on payments made to each surrendering U.S. Holder, each such U.S. Holder should either (x) provide such Holder’s correct taxpayer identification number (“TIN”) by completing a copy of the substitute IRS Form W-9 enclosed with this Company Notice, certifying that (1) such Holder is a “United States person” (as defined in section 7701(a)(30) of the Code, (2) the TIN provided is correct (or that such U.S. Holder is awaiting a TIN) and (3) that such U.S. Holder is not subject to backup withholding because: (a) such Holder is exempt from backup withholding, (b) such Holder has not been notified by the IRS that such Holder is subject to backup withholding as a result of a failure to report all interest or dividends, or (c) the IRS has notified such U.S. Holder that he, she or it is no longer subject to backup withholding, and provide such completed Form W-9 or (y) otherwise establish an exemption. Otherwise, backup withholding may apply until such Holder furnishes such Holder’s TIN (and, if such Holder has not already done so, the completed substitute IRS Form W-9

12

described above). If a tendering U.S. Holder does not provide the correct TIN or an adequate basis for exemption, such Holder may be subject to a $50 penalty imposed by the IRS, and payments made with respect to the tendered Securities may be subject to backup withholding. If withholding results in an overpayment of taxes, a refund may be obtained.

     To prevent backup withholding, non-U.S. Holders should (i) submit a properly completed IRS Form W-8BEN, certifying under penalties of perjury to the holder’s foreign status or (ii) otherwise establish an exemption. IRS Forms W-8BEN may be obtained from the Paying Agent.

     Certain Holders (including, among others, corporations and certain foreign individuals) are exempt recipients not subject to backup withholding requirements. See the enclosed copy of the IRS Substitute Form W-9, Request for Taxpayer Identification Number and Certification, and the Guidelines for Certification of taxpayer Identification Number on Substitute Form W-9. To avoid possible erroneous backup withholding, exempt U.S. Holders, while not required to file Substitute Form W-9, should complete and return the Substitute Form W-9 (checking the “Exempt” box on its face).

     See the enclosed Guidelines for Certification of Taxpayer Identification Number on Substitute Form W-9 for additional information and instructions

     11. Additional Information. The Company is subject to the reporting and other informational requirements of the Exchange Act and, in accordance therewith, files reports, proxy statements and other information with the SEC. Such reports, proxy statements and other information can be inspected and copied at the Public Reference Section of the SEC located at Room 1024, Judiciary Plaza, 450 Fifth Street, N.W., Washington D.C. 20549. Copies of such material can be obtained from the Public Reference Section of the SEC at prescribed rates. Such material may also be accessed electronically by means of the SEC’s home page on the Internet at www.sec.gov. Such reports and other information concerning the Company may also be inspected at the offices of the NASDAQ located at One Liberty Plaza, 50th Floor, New York, New York 10006.

     The Company has filed with the SEC a Tender Offer Statement on Schedule TO-I, pursuant to Section 13(e) of the Exchange Act and Rule 13e-4 promulgated thereunder, furnishing certain information with respect to the Put Option. The Tender Offer Statement on Schedule TO-I, together with any exhibits and any amendments thereto, may be examined and copies may be obtained at the same places and in the same manner as set forth above.

     The documents listed below (as such documents may be amended from time to time) contain important information about the Company and its financial condition.

13

     In the event of conflicting information in these documents, the information in the latest filed documents should be considered correct.

     12. No Solicitations. The Company has not employed any persons to make solicitations or recommendations in connection with the Put Option.

     13. Definitions. All capitalized terms used but not specifically defined this Company Notice shall have the meanings given to such terms in the Indenture and the Securities.

     14. Conflicts. In the event of any conflict between this Company Notice on the one hand and the terms of the Indenture or the Securities or any applicable laws on the other hand, the terms of the Indenture or the Securities or applicable laws, as the case may be, will control.

     None of the Company or its board of directors or employees are making any recommendation to any Holder as to whether to surrender or refrain from surrendering Securities for purchase pursuant to this Company Notice. Each Holder must make such Holder’s own decision whether to surrender such Holder’s Securities for purchase and, if so, the principal amount of Securities to surrender based on their own assessment of current market value and other relevant factors.

14

ANNEX A

BOARD OF DIRECTORS AND EXECUTIVE OFFICERS

     The following table sets forth the names of each of the members of the Company’s board of directors and each of the Company’s executive officers.

Directors

Executive Officers

     The business address of each person set forth above is c/o Amgen Inc., One Amgen Center Drive, Thousand Oaks, California 91320-1799 and the telephone number there is (805) 447-1000.

15

Exhibit 99(a)(1)(B)

CERTIFICATE OF AWAITING TAXPAYER IDENTIFICATION NUMBER

     I certify under penalties of perjury that a taxpayer identification number has not been issued to me, and either (a) I have mailed or delivered an application to receive a taxpayer identification number to the appropriate Internal Revenue Service Center or Social Security Administration Office or (b) I intend to mail or deliver an application in the near future. I understand that if I do not provide a taxpayer identification number by the time of payment, 28% of all reportable payments made to me may be withheld until I provide a taxpayer identification number to the Paying Agent.

1

GUIDELINES FOR CERTIFICATION OF TAXPAYER IDENTIFICATION
NUMBER ON SUBSTITUTE FORM W-9

     Guidelines for Determining the Proper Identification Number to Give the Payer—Social Security numbers have nine digits separated by two hyphens: i.e., 000-00-0000. Employer Identification numbers have nine digits separated by only one hyphen: i.e., 00-0000000. The table below will help determine the number to give the payer.

(1) List first and circle the name of the person whose number you furnish. If only one person on a joint account has a social security number, that person’s social security number must be furnished.

(2) Circle the minor’s name and furnish the minor’s social security number.

(3) You must show your individual name, but you may also enter your business or “doing business as” name. You may use either your social security number or your employer identification number (if you have one).

(4) List first and circle the name of the legal trust, estate or pension trust.

NOTE: If no name is circled when there is more than one name listed, the number will be considered to be that of the first name listed.

3

GUIDELINES FOR CERTIFICATION OF TAXPAYER IDENTIFICATION
NUMBER ON SUBSTITUTE FORM W-9

Obtaining a Number

     If you don’t have a taxpayer identification number, obtain Form SS-5, Application for a Social Security Number Card, or Form SS-4, Application for Employer Identification Number, at the local office of the Social Security Administration or the Internal Revenue Service and apply for a number.

Payees Exempt from Backup Withholding

     Payees specifically exempted from backup withholding on ALL payments include the following:

     Other payees that may be exempt from back-up withholding include the following:

Payments of dividends and patronage dividends not generally subject to backup withholding include the following:

4

Payments of interest not generally subject to backup withholding include the following:

     Exempt payees described above should file Form W-9 to avoid possible erroneous backup withholding. FILE THIS FORM WITH THE PAYER, FURNISH YOUR TAXPAYER IDENTIFICATION NUMBER, WRITE “EXEMPT” ON THE FACE OF THE FORM, SIGN AND DATE THE FORM AND RETURN IT TO THE PAYER.

     Certain payments other than interest, dividends, and patronage dividends that are not subject to information reporting are also not subject to backup withholding. For details, see Code sections 6041, 6041A(a), 6042, 6044, 6045, 6049, 6050A and 6050N, and their regulations.

     Privacy Act Notice—Section 6109 requires most recipients of dividend, interest, or other payments to give their correct taxpayer identification numbers to payers who must report the payments to IRS. The IRS uses the numbers for identification purposes and to help verify the accuracy of tax returns. The IRS may also provide this information to the Department of Justice for civil and criminal litigation and to cities, states and the District of Columbia to carry out their tax laws. We may also disclose this information to other countries under a tax treaty, or to Federal or state agencies to enforce Federal non-tax criminal laws and to combat terrorism. Payers must be given the numbers whether or not recipients are required to file tax returns. Payers must generally withhold 28% of taxable interest, dividend, and certain other payments to a payee who does not furnish a taxpayer identification number to a payer. Certain penalties may also apply.

     Unless otherwise indicated, all section references are to the Internal Revenue Code of 1986, as amended.

Penalties

FOR ADDITIONAL INFORMATION
CONTACT YOUR TAX CONSULTANT OR
THE INTERNAL REVENUE SERVICE.

5

Exhibit 99(a)(5)

AMGEN ANNOUNCES PUT OPTION NOTIFICATION FOR LIQUID YIELD OPTION NOTES DUE 2032

     THOUSAND OAKS, Calif, JANUARY 31, 2005— Amgen Inc. (Nasdaq:AMGN), the world’s largest biotechnology company, today announced that it has notified holders of Amgen’s Liquid Yield Option™ Notes due 2032 (Zero Coupon—Senior) (the “LYONs”) that they have the right to surrender their LYONs for purchase by Amgen pursuant to the terms of the Indenture for the LYONs (the “Put Option”). The Put Option expires on March 1, 2005.

     As required by law, Amgen will file a Tender Offer Statement on Schedule TO with the Securities and Exchange Commission later today. In addition, documents specifying the terms, conditions and procedures for surrendering and withdrawing LYONs for purchase will be available through The Depository Trust Company and the paying agent. Neither Amgen nor its board of directors or employees have made or are making any representation or recommendation as to whether or not any holder should surrender any LYONs.

     The Put Option entitles each holder of the LYONs to require Amgen to purchase all or any part of such holder’s LYONs at a price equal to $738.68 per $1,000 of principal amount at maturity. Under the terms of the LYONs, Amgen has the option to pay the purchase price with cash, common stock or a combination of cash and stock. Amgen has elected to pay the purchase price solely with cash. If all outstanding LYONs are surrendered for purchase pursuant to the Put Option, the aggregate cash purchase price will be approximately $2.9 billion. The LYONs are convertible at any time before maturity into 8.8601 shares of Amgen’s common stock per $1,000 principal amount at maturity, subject to adjustment under certain circumstances.

     LYONs holders’ opportunity to surrender LYONs for purchase pursuant to the Put Option will commence on January 31, 2005, and will terminate at 5:00 p.m., New York City time, on March 1, 2005. In order to exercise the Put Option, a holder must follow the procedures set forth in Amgen’s notice to holders. Holders may withdraw any LYONs previously surrendered for purchase at any time prior to 5:00 p.m., New York City time, on March 1, 2005.

About Amgen

     Amgen is a global biotechnology company that discovers, develops, manufactures and markets important human therapeutics based on advances in cellular and molecular biology.

Forward-Looking Statements

     This news release contains forward-looking statements that involve significant risks and uncertainties, including those discussed below and others that can be found in our Form 10-K for the year ended December 31, 2003, and in our periodic reports on Form 10-Q and Form 8-K. Amgen is providing this information as of the date of this news release and does not undertake any obligation to update any forward-looking statements contained in this document as a result of new information, future events or otherwise.

     No forward-looking statement can be guaranteed and actual results may differ materially from those we project. Amgen’s results may be affected by our ability to successfully market both new and existing products domestically and internationally, sales growth of recently launched products, difficulties or

delays in manufacturing our products, and regulatory developments (domestic or foreign) involving current and future products and manufacturing facilities. In addition, sales of our products are affected by reimbursement policies imposed by first party payors, including governments, private insurance plans and managed care providers, and may be affected by domestic and international trends toward managed care and healthcare cost containment, as well as possible US legislation affecting pharmaceutical pricing and reimbursement. Government regulations and reimbursement policies may affect the development, usage and pricing of our products. Furthermore, our research, testing, pricing, marketing and other operations are subject to extensive regulation by domestic and foreign government regulatory authorities. We, or others could identify side effects or manufacturing problems with our products after they are on the market. In addition, we compete with other companies with respect to some of our marketed products as well as for the discovery and development of new products. Discovery or identification of new product candidates cannot be guaranteed and movement from concept to product is uncertain; consequently, there can be no guarantee that any particular product candidate will be successful and become a commercial product. In addition, while we routinely obtain patents for our products and technology, the protection offered by our patents and patent applications may be challenged, invalidated or circumvented by our competitors. Further, some raw materials, medical devices, and component parts for our products are supplied by sole first party suppliers.

CONTACT: Amgen, Thousand Oaks
Christine Cassiano, 805-447-4587 (media)
Arvind Sood, 805-447-1060 (investors)

2