<TABLE> <S> <C>
<PAGE>
<ARTICLE> 5
<LEGEND>
THIS SCHEDULE CONTAINS SUMMARY FINANCIAL INFORMATION EXTRACTED FROM THE
CONSOLIDATED CONDENSED FINANCIAL STATEMENTS OF ONEOK, INC. FOR THE SIX MONTHS
ENDED JUNE 30, 2000, AND IS QUALIFIED IN ITS ENTIRETY BY REFERENCE TO SUCH
FINANCIAL STATEMENTS.
</LEGEND>
<MULTIPLIER> 1,000
<S> <C>
<PERIOD-TYPE> 6-MOS
<FISCAL-YEAR-END> DEC-31-2000
<PERIOD-START> JAN-01-2000
<PERIOD-END> JUN-30-2000
<CASH> 7,137
<SECURITIES> 0
<RECEIVABLES> 841,290
<ALLOWANCES> 0
<INVENTORY> 161,018
<CURRENT-ASSETS> 1,786,863
<PP&E> 3,980,877
<DEPRECIATION> 1,061,365
<TOTAL-ASSETS> 5,372,104
<CURRENT-LIABILITIES> 1,869,891
<BONDS> 1,357,869
0
199
<COMMON> 316
<OTHER-SE> 1,195,120
<TOTAL-LIABILITY-AND-EQUITY> 5,372,104
<SALES> 2,211,079
<TOTAL-REVENUES> 2,211,079
<CGS> 1,578,529
<TOTAL-COSTS> 2,026,390
<OTHER-EXPENSES> 0
<LOSS-PROVISION> 0
<INTEREST-EXPENSE> 50,328
<INCOME-PRETAX> 146,125
<INCOME-TAX> 58,056
<INCOME-CONTINUING> 88,069
<DISCONTINUED> 0
<EXTRAORDINARY> 0
<CHANGES> 2,115
<NET-INCOME> 90,184
<EPS-BASIC> 2.45
<EPS-DILUTED> 1.83
</TABLE>