<TABLE> <S> <C>
<PAGE>
<ARTICLE> 5
<LEGEND>
THIS SCHEDULE CONTAINS SUMMARY FINANCIAL INFORMATION EXTRACTED FROM THE
UNAUDITED FINANCIAL STATEMENT OF ATLAS-ENERGY FOR THE NINETIES-PUBLIC #6 LTD.
AND IS QUALIFIED IN ITS ENTIRETY BY REFERENCE TO SUCH FINANCIAL STATEMENTS.
</LEGEND>
<MULTIPLIER> 1,000
<S> <C> <C>
<PERIOD-TYPE> 3-MOS 9-MOS
<FISCAL-YEAR-END> DEC-31-1999 DEC-31-1999
<PERIOD-START> JUN-30-2000 DEC-31-1999
<PERIOD-END> SEP-30-2000 SEP-30-2000
<CASH> 22,623 22,623
<SECURITIES> 0 0
<RECEIVABLES> 319,165 319,165
<ALLOWANCES> 0 0
<INVENTORY> 0 0
<CURRENT-ASSETS> 341,788 341,788
<PP&E> 10,355,659 10,355,659
<DEPRECIATION> (2,932,175) (2,932,175)
<TOTAL-ASSETS> 7,765,272 7,765,272
<CURRENT-LIABILITIES> 15,230 15,230
<BONDS> 0 0
0 0
0 0
<COMMON> 0 0
<OTHER-SE> 7,750,042 7,750,042
<TOTAL-LIABILITY-AND-EQUITY> 7,765,272 7,765,272
<SALES> 418,000 1,181,156
<TOTAL-REVENUES> 425,332 1,195,589
<CGS> 52,266 147,154
<TOTAL-COSTS> 52,266 147,155
<OTHER-EXPENSES> 245,550 765,805
<LOSS-PROVISION> 0 0
<INTEREST-EXPENSE> 0 0
<INCOME-PRETAX> 127,516 282,630
<INCOME-TAX> 0 0
<INCOME-CONTINUING> 127,516 282,630
<DISCONTINUED> 0 0
<EXTRAORDINARY> 0 0
<CHANGES> 0 0
<NET-INCOME> 127,516 282,630
<EPS-BASIC> 0 0
<EPS-DILUTED> 0 0
</TABLE>