<TABLE> <S> <C>
<PAGE>
<ARTICLE> 5
<CIK> 0001022079
<NAME> QUEST DIAGNOSTICS INCORPORATED
<MULTIPLIER> 1,000
<CURRENCY>U.S. DOLLAR
<S> <C> <C>
<PERIOD-TYPE> 9-MOS 9-MOS
<FISCAL-YEAR-END> DEC-31-2000 DEC-31-1999
<PERIOD-START> JAN-01-2000 JAN-01-1999
<PERIOD-END> SEP-30-2000 SEP-30-1999
<EXCHANGE-RATE> 1 1
<CASH> 161,786 36,799
<SECURITIES> 0 0
<RECEIVABLES> 651,346 640,575
<ALLOWANCES> 137,955 86,891
<INVENTORY> 43,012 51,376
<CURRENT-ASSETS> 1,049,348 875,011
<PP&E> 424,081 445,000
<DEPRECIATION> 426,134 358,786
<TOTAL-ASSETS> 3,006,154 2,826,565
<CURRENT-LIABILITIES> 987,176 638,810
<BONDS> 0 0
1,000 1,000
0 0
<COMMON> 1,575,686 1,468,001
<OTHER-SE> (590,049) (612,984)
<TOTAL-LIABILITY-AND-EQUITY> 3,006,154 2,826,565
<SALES> 0 0
<TOTAL-REVENUES> 2,584,828 1,390,717
<CGS> 1,554,216 859,569<F1>
<TOTAL-COSTS> 2,308,116 1,273,408
<OTHER-EXPENSES> 4,474 34,766
<LOSS-PROVISION> 181,646 81,775
<INTEREST-EXPENSE> 89,430 31,392
<INCOME-PRETAX> 147,428 33,026
<INCOME-TAX> 70,739 19,763
<INCOME-CONTINUING> 76,689 13,263
<DISCONTINUED> 0 0
<EXTRAORDINARY> 0 (2,139)
<CHANGES> 0 0
<NET-INCOME> 76,689 11,124
<EPS-BASIC> 1.72 0.34
<EPS-DILUTED> 1.64 0.34
<FN>
<F1>During the fourth quarter of 1999, the Company reclassified certain expense
items, primarily related to a portion of occupancy costs and professional
liability insurance expense items, from selling, general and administrative
expenses to cost of services, to better reflect the cost of performing testing.
</FN>
</TABLE>