<ARTICLE> 5
<LEGEND>
THIS SCHEDULE CONTAINS SUMMARY FINANCIAL INFORMATION EXTRACTED FROM ONYX
PHARMACEUTICALS, INC.'S BALANCE SHEET DATED DECEMBER 31, 1999, AND
STATEMENT OF OPERATIONS FOR THE YEAR ENDED DECEMBER 31, 1999, AND IS
QUALIFIED IN ITS ENTIRETY BY REFERENCE TO SUCH FINANCIAL STATEMENTS.
</LEGEND>
<MULTIPLIER> 1,000

                             
<PERIOD-TYPE>                   YEAR
<FISCAL-YEAR-END>                          DEC-31-1999
<PERIOD-START>                              JAN-1-1999
<PERIOD-END>                               DEC-31-1999
<CASH>                                          12,671
<SECURITIES>                                     1,792
<RECEIVABLES>                                    3,300
<ALLOWANCES>                                         0
<INVENTORY>                                          0
<CURRENT-ASSETS>                                18,223
<PP&E>                                          12,146
<DEPRECIATION>                                   9,146
<TOTAL-ASSETS>                                  21,628
<CURRENT-LIABILITIES>                           11,450
<BONDS>                                          2,382
<PREFERRED-MANDATORY>                                0
<PREFERRED>                                          0
<COMMON>                                            12
<OTHER-SE>                                       7,650
<TOTAL-LIABILITY-AND-EQUITY>                    21,628
<SALES>                                              0
<TOTAL-REVENUES>                                13,324
<CGS>                                                0
<TOTAL-COSTS>                                   28,968
<OTHER-EXPENSES>                                     0
<LOSS-PROVISION>                                     0
<INTEREST-EXPENSE>                                 316
<INCOME-PRETAX>                               (14,802)
<INCOME-TAX>                                         0
<INCOME-CONTINUING>                           (14,802)
<DISCONTINUED>                                       0
<EXTRAORDINARY>                                      0
<CHANGES>                                            0
<NET-INCOME>                                  (14,802)
<EPS-BASIC>                                     (1.29)
<EPS-DILUTED>                                   (1.29)