<TABLE> <S> <C>
<PAGE>
<ARTICLE> 5
<LEGEND>
THIS SCHEDULE CONTAINS SUMMARY FINANCIAL INFORMATION EXTRACTED FROM THE
FINANCIAL STATEMENTS OF CLEAN HARBORS, INC. FOR THE SIX MONTH PERIOD ENDED
JUNE 30, 2000.
</LEGEND>
<CIK> 0000822818
<NAME> CLEAN HARBORS, INC.
<MULTIPLIER> 1,000
<S> <C>
<PERIOD-TYPE> 6-MOS
<FISCAL-YEAR-END> DEC-31-1999
<PERIOD-START> JAN-01-2000
<PERIOD-END> JUN-30-2000
<CASH> 3,096
<SECURITIES> 1,658
<RECEIVABLES> 52,495
<ALLOWANCES> 1,293
<INVENTORY> 2,873
<CURRENT-ASSETS> 60,645
<PP&E> 142,236
<DEPRECIATION> 85,074
<TOTAL-ASSETS> 154,231
<CURRENT-LIABILITIES> 92,817
<BONDS> 23,561
0
1
<COMMON> 111
<OTHER-SE> 36,438
<TOTAL-LIABILITY-AND-EQUITY> 154,231
<SALES> 0
<TOTAL-REVENUES> 114,979
<CGS> 0
<TOTAL-COSTS> 81,904
<OTHER-EXPENSES> 25,701
<LOSS-PROVISION> 342
<INTEREST-EXPENSE> 4,603
<INCOME-PRETAX> 2,429
<INCOME-TAX> 230
<INCOME-CONTINUING> 2,199
<DISCONTINUED> 0
<EXTRAORDINARY> 0
<CHANGES> 0
<NET-INCOME> 2,199
<EPS-BASIC> 0.18
<EPS-DILUTED> 0.18
</TABLE>