<ARTICLE>                     5
<CIK>                         0001022079
<NAME>                        Quest Diagnostics Incorporated
<MULTIPLIER>                                   1000
<CURRENCY>                                     US$

       

                           
<PERIOD-TYPE>                                     6-MOS
<FISCAL-YEAR-END>                           DEC-31-1998
<PERIOD-START>                              JAN-01-1998
<PERIOD-END>                                JUN-30-1998
<EXCHANGE-RATE>                                       1
<CASH>                                          152,686
<SECURITIES>                                          0
<RECEIVABLES>                                   243,238
<ALLOWANCES>                                     70,262
<INVENTORY>                                      29,221
<CURRENT-ASSETS>                                551,095
<PP&E>                                          244,396
<DEPRECIATION>                                  341,654
<TOTAL-ASSETS>                                1,364,081
<CURRENT-LIABILITIES>                           278,396
<BONDS>                                               0
<PREFERRED-MANDATORY>                                 0
<PREFERRED>                                       1,000
<COMMON>                                      1,202,610
<OTHER-SE>                                     (643,296)
<TOTAL-LIABILITY-AND-EQUITY>                  1,364,081
<SALES>                                         734,614
<TOTAL-REVENUES>                                734,614
<CGS>                                           435,846
<TOTAL-COSTS>                                   672,425
<OTHER-EXPENSES>                                  1,364
<LOSS-PROVISION>                                 44,999
<INTEREST-EXPENSE>                               18,150
<INCOME-PRETAX>                                  31,929
<INCOME-TAX>                                     16,444
<INCOME-CONTINUING>                              15,485
<DISCONTINUED>                                        0
<EXTRAORDINARY>                                       0
<CHANGES>                                             0
<NET-INCOME>                                     15,485
<EPS-PRIMARY>                                      0.52
<EPS-DILUTED>                                      0.51