SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 Form 11-K FOR ANNUAL REPORTS OF EMPLOYEE STOCK PURCHASE, SAVINGS AND SIMILAR PLANS PURSUANT TO SECTION 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 [X] ANNUAL REPORT PURSUANT TO SECTION 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the fiscal year ended December 31, 1998 OR [ ] TRANSITION REPORT PURSUANT TO SECTION 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from 		to Commission file number 2-84723 THE SCHERING-PLOUGH PUERTO RICO EMPLOYEES' RETIREMENT SAVINGS PLAN Schering-Plough Corporation One Giralda Farms P.O. Box 1000 Madison, New Jersey 07940 THE SCHERING-PLOUGH PUERTO RICO EMPLOYEES' RETIREMENT SAVINGS PLAN TABLE OF CONTENTS Page INDEPENDENT AUDITORS' REPORT 	3 FINANCIAL STATEMENTS: 	Statements of Net Assets Available for Benefits 		as of December 31, 1998 and 1997 	4 	Statement of Changes in Net Assets Available for Benefits 		for the Year Ended December 31, 1998	 5 	Notes to Financial Statements 	6 - 11 SUPPLEMENTAL SCHEDULES: 	SCHEDULE Schedule of Assets Held for Investment Purposes 		December 31, 1998 	I 	Schedule of Transactions in Excess of 5% 		of Plan Assets for the Year Ended December 31, 1998	 II EXHIBITS: 	Exhibit I - Independent Auditors' Consent Supplemental schedules not included herein are omitted due to the absence of conditions under which they are required. 2 INDEPENDENT AUDITORS' REPORT The Schering-Plough Puerto Rico Employees' Retirement Savings Plan: We have audited the accompanying statements of net assets available for benefits of The Schering-Plough Puerto Rico Employees' Retirement Savings Plan (the "Plan") as of December 31, 1998 and 1997, and the related statement of changes in net assets available for benefits for the year ended December 31, 1998. 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 in accordance with generally accepted auditing standards. Those standards require that we plan and perform the audit 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. An audit also includes assessing the accounting principles used and significant estimates made by management, as well as evaluating the overall financial statement presentation. We believe that our audits provide a reasonable basis for our opinion. In our opinion, such financial statements present fairly, in all material respects, the net assets available for benefits of the Plan as of December 31, 1998 and 1997, and the changes in net assets available for benefits for the year ended December 31, 1998, in conformity with generally accepted accounting principles. Our audits were conducted for the purpose of forming an opinion on the basic financial statements taken as a whole. The supplemental schedules of Assets Held for Investment Purposes and Transactions in Excess of 5% of Plan Assets are presented for the purpose of additional analysis and are not a required part of the basic financial statements, but are 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. These schedules are the responsibility of the Plan's management. Such schedules have been subjected to the auditing procedures applied in our audit of the basic 1998 financial statements and, in our opinion, are fairly stated in all material respects when considered in relation to the basic financial statements taken as a whole. _________________________________________ /s/ Deloitte & Touche LLP San Juan, Puerto Rico May 11, 1999 3 THE SCHERING-PLOUGH PUERTO RICO EMPLOYEES' RETIREMENT SAVINGS PLAN STATEMENTS OF NET ASSETS AVAILABLE FOR BENEFITS DECEMBER 31, 1998 AND 1997 1998 1997 Vanguard 500 Index Fund			 $ 7,214,850 $ 5,228,436 Vanguard Windsor Fund 2,300,156 2,610,599 Vanguard Treasury Money Market Fund		 1,317,590 1,296,315 Vanguard Short-Term Corporate Fund		 432,973 364,238 Vanguard Wellington Fund 124,889 97,393 Vanguard International Growth Fund 106,880 69,267 Vanguard Explorer Fund 50,842 52,893 Total Vanguard Registered Investment Company Assets 11,548,180 9,719,141 Schering-Plough Stock Fund 5,815,884 2,448,942 Loan Fund 1,416,221 1,173,039 NET ASSETS AVAILABLE FOR BENEFITS $18,780,285 $13,341,122 See notes to financial statements. 4 THE SCHERING-PLOUGH PUERTO RICO EMPLOYEES' RETIREMENT SAVINGS PLAN STATEMENT OF CHANGES IN NET ASSETS AVAILABLE FOR BENEFITS YEAR ENDED DECEMBER 31, 1998 ADDITIONS TO NET ASSETS ATTRIBUTED TO: Investment income: Interest and dividends $ 561,223 Net appreciation in fair value of investments 3,424,279 Total 3,985,502 Participant contributions 1,812,009 Other receipts - rollovers and transfers in 52,025 Total additions 5,849,536 DEDUCTIONS FROM NET ASSETS ATTRIBUTED TO: Benefit payments 410,333 Other deductions 40 Total deductions 410,373 NET INCREASE 5,439,163 NET ASSETS AVAILABLE FOR BENEFITS: Beginning of year 13,341,122 End of year $18,780,285 See notes to financial statements. 5 THE SCHERING-PLOUGH PUERTO RICO EMPLOYEES' RETIREMENT SAVINGS PLAN NOTES TO FINANCIAL STATEMENTS 1.	GENERAL The Schering-Plough Puerto Rico Employees' Retirement Savings Plan (the "Plan") is a defined contribution plan established effective April 1, 1990. The Plan is intended to encourage retirement savings by eligible employees of Schering-Plough Products, Inc. (the "Sponsor") and any of its affiliated companies that adopts the Plan. Vanguard Fiduciary Trust Company ("VFTC"), the trustee, is a trust company incorporated under Chapter 10 of the Pennsylvania Banking Code, and a wholly-owned subsidiary of The Vanguard Group, Inc. ("Vanguard"). All Puerto Rico employees of Schering-Plough Products, Inc. and Schering-Plough del Caribe, Inc. are eligible to participate in the Plan on the date of employment. There were 1,047 and 944 participants in the Plan at December 31, 1998 and 1997, respectively. The participants may elect to have their salary deferral contributions allocated to any of the investment funds available under this Plan. 2.	SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Basis of Accounting The accounts of the Plan have been prepared on an accrual basis in accordance with generally accepted accounting principles. The financial statements were prepared in accordance with the financial reporting requirements of the Employee Retirement Income Security Act of 1974 ("ERISA") as permitted by the Securities and Exchange Commission. Investment Valuation and Income Recognition The Plan's investments are stated at fair value. Shares of registered investment companies are valued at quoted market prices which represent the net asset value of shares held by the Plan at year end. 6 The Schering-Plough Stock Fund is valued using the unit accounting method whereby a participant's account value is expressed in units of participation rather than number of shares of Schering-Plough common stock. At December 31, 1998 and 1997, there were 5,850 and 4,369 units of participation in the Schering-Plough Stock Fund, respectively. The net asset value per unit was $994.25 and $560.51 at December 31, 1998 and 1997, respectively. The closing stock prices of Schering-Plough Corporation at December 31, 1998 and December 31, 1997 were $55 1/4 and $31 1/16, respectively; the closing price on May 11, 1999 was $48 9/16. Purchases and sales of securities are recorded on a trade- date basis. Interest income is recorded on the accrual basis. Dividends are recorded on the ex-dividend date, and reinvested in Schering-Plough common stock units. Payment of Benefits Benefit payments are recorded when paid. 3.	PLAN DESCRIPTION The following is a description of the Plan for general information purposes. Participants should refer to the Plan document for more complete information. Salary Deferral Contributions The Plan is designed to permit eligible employees to elect to have a portion of their salary contributed to the Plan on their behalf ("salary deferral contributions"). Under the provisions of the Plan, salary deferral contributions can range from 1% to 10% of the employee's earnings, in increments of 1%, subject to certain limitations. Salary deferral contributions and any earnings accrued thereon are fully and immediately vested to the participant. Participant Accounts Each participant's account is credited with the participant's contribution and allocations of Plan earnings. Allocations are based on participant earnings or account balances, as defined. Participants have a nonforfeitable right to their contributions plus actual earnings thereon which vest fully and immediately. 7 Investment Options Upon enrollment in the Plan, a participant may direct their contributions into any of the following Vanguard investment options: 500 Index Fund - Designed to provide returns which correspond to the performance of Standard & Poor's 500 Composite Stock Price Index. Windsor Fund - Primarily equity securities with the objective of providing long-term capital growth. Treasury Money Market Fund - Exclusively U.S. Treasury securities with maturities of 13 months or less with the objective of providing current income based on current market interest rates, with preservation of principal and liquidity. Short-Term Corporate Fund - A diversified portfolio primarily consisting of short-term corporate bonds. Wellington Fund - Primarily equity and fixed income securities with the objective of providing current income and capital appreciation. International Growth Fund - A non-U.S. equity portfolio, primarily investing in securities of issuers within Europe, Asia and the Far East. Explorer Fund - Primarily equity securities of smaller companies with the objective of providing above average capital appreciation but with a potentially higher level of risk. Schering-Plough Stock Fund Participants may contribute to a maximum investment election of 50% of the Salary Deferral Contribution into this fund. 8 Loan Fund The Plan allows participants to borrow against their fund accounts up to a maximum of the lesser of one half of their account or $50,000. These loans, which are secured by the participants' individual fund accounts, bear a fixed rate of interest as determined to be reasonable by The Schering- Plough Puerto Rico Employees' Retirement Savings Plan Committee, and are repayable over periods not exceeding five years, except loans relating to a principal residence which are repayable over a period not to exceed 20 years. Payment of Benefits On termination of service due to death, disability or retirement, a participant may elect to receive either a lump- sum amount or annual installments not to exceed the life expectancy of the participant or the life expectancy of the beneficiary. For termination of service due to other reasons, a participant may receive the value of the account as a lump sum distribution. Distribution of all or a portion of a participant's account, prior to termination of employment, may be granted by the Company in the case of financial hardship. Effective January 1, 1998, active participants may elect to withdraw all or a portion of their accounts at any time after age 70. 4.	PLAN TERMINATION Although it has not expressed any intent to do so, the Sponsor has the right to terminate the Plan subject to provisions of ERISA. 5.	TAX STATUS In March 1992, the Plan received a favorable determination letter issued by the Puerto Rico Department of Treasury as to the Plan's qualified status under Sections 165(a) and (e) of the Puerto Rico Income Tax Act of 1954, as amended. As long as the Plan is qualified under Puerto Rico income tax laws and regulations, participants will not be taxed on salary- deferred contributions or on investment earnings on such contributions at the time such contributions and investment earnings are received by the trustee under the Plan, but will be subject to tax thereon at such time as they receive distributions from the Plan. 9 6.	ADMINISTRATION OF PLAN ASSETS Contributions are held and managed by the trustee, VFTC, which invests cash received, interest and dividend income and makes distributions to the participants. The trustee also administers the collection of interest and principal on the participant loans. Certain administrative functions are performed by officers or employees of the Sponsor. No such officer or employee receives compensation from the Plan. All plan administration expenses are borne by the Sponsor. 10 7. FUND INFORMATION Investment income, contributions and benefit payments are as follows for the year ended December 31, 1998: Vanguard Vanguard Vanguard Schering- Vanguard Vanguard Treasury Short- Van- Inter- Vanguard Plough Term guard national 500 Index Windsor Money Corp- Well- Growth Explorer Stock Loan orate ington Fund Fund Market Fund Fund Fund Fund Fund Fund Total Fund Investment Income: Interest and Dividends $ 107,624 $202,140 $ 62,841 23,551 $ 13,663 $ 2,129 $ 444 40,521 $ 108,310 $ 561,223 Net Appreciation (depreciation) in fair value of investments 1,448,455 (193,125) - 757 83 11,020 1,225 2,155,864 - 3,424,279 Total Investment Income $1,556,079 $ 9,015 $ 62,841 $24,308 $ 13,746 $ 13,149 $ 1,669 $2,196,385 $ 108,310 $3,985,502 Participant Contributions $ 630,184 $373,755 $ 127,721 $53,689 $ 36,361 $ 31,002 $ 18,478 $ 540,819 $ - $1,812,009 Other receipts - - Rollovers and Transfers In $ 10,405 $ 10,405 $ 10,405 $10,405 $ 10,405 $ - $ - $ - $ - $ 52,025 Benefit Payments $ 180,947 $ 67,438 $ 46,029 $14,169 $ 5,896 $ 3,051 $ 752 $ 40,145 $ 51,906 $ 410,333 THE SCHERING-PLOUGH PUERTO RICO EMPLOYEES' RETIREMENT SAVINGS PLAN	SCHEDULE I ITEM 27a - SCHEDULE OF ASSETS HELD FOR INVESTMENT PURPOSES DECEMBER 31, 1998 Identity Shares/ Current of issue Participants Units Cost Value Vanguard 500 Index Fund* 841 63,316 $4,073,846 $7,214,850(1) Vanguard Windsor Fund* 522 147,730 2,395,616 2,300,156(1) Vanguard Treasury Money Market Fund* 363 1,317,590 1,317,590 1,317,590(1) Vanguard Short-Term Corporate Fund* 170 39,942 430,294 432,973 Vanguard Wellington Fund* 84 4,255 122,752 124,889 Vanguard International Growth Fund* 61 5,694 99,738 106,880 Vanguard Explorer Fund* 53 897 48,737 50,842 Schering-Plough Stock Fund 672 5,850(2) 2,911,705 5,815,884(1) Outstanding loan balance - various loans; 7% to 10%, due in one to five years 368 1,416,221 1,416,221(1) Total Assets Held for Investment Purposes $12,816,499 $18,780,285 *Registered Investment Company. (1) Indicates investment represents five percent or more of the net assets available for benefits. (2) Represents Schering-Plough Stock Fund units. THE SCHERING-PLOUGH PUERTO RICO EMPLOYEES' RETIREMENT SAVINGS PLAN			SCHEDULE II ITEM 27d - SCHEDULE OF TRANSACTIONS IN EXCESS OF 5% OF PLAN ASSETS YEAR ENDED DECEMBER 31, 1998 Identity Cost of Number of Proceeds Number Net Gain of Issue Purchases Purchases * From Sales of Sales * (Loss) Vanguard 500 Index Fund $1,446,301 98 $908,103 96 $ 75,734 Vanguard Windsor Fund 779,904 53 896,828 108 (9,329) Vanguard Treasury Money Market Fund 594,364 88 573,089 86 - Schering-Plough Stock Fund 1,673,631 127 463,147 57 102,531 * Represents the number of days a trade occurred in 1998. EXHIBIT I INDEPENDENT AUDITORS' CONSENT We consent to the incorporation by reference in Registration Statements No. 2-83963, No. 33-19013, No. 33-50606 and No. 333- 30331 on Form S-8, Registration Statement No. 333-853 on Form S- 3, Post-Effective Amendment No. 1 to Registration Statement No. 2-84723 on Form S-8, Post-Effective Amendment No. 1 to Registration No. 2-80012 on Form S-3, Post-Effective Amendment No. 1 to Registration Statement No. 2-77740 on Form S-3 and Registration Statements No. 333-12909 and No. 333-30355 on Form S-3 of our report dated May 11, 1999 appearing in this Annual Report on Form 11-K of The Schering-Plough Puerto Rico Employees' Retirement Savings Plan for the year ended December 31, 1998. __________________________________________ /s/ Deloitte & Touche LLP San Juan, Puerto Rico June 24, 1999 SIGNATURES Pursuant to the requirements of the Securities Exchange Act of 1934, the trustees (or other persons who administer the Plan) have duly caused this Annual Report to be signed on its behalf by the undersigned hereunto duly authorized. The Schering-Plough Puerto Rico Employees' Retirement Savings Plan Date: June 17, 1999			By: /s/ Vincent Sweeney 							Name: Vincent Sweeney 							Title: Plan Administrator 	- -