<TABLE> <S> <C>

<PAGE>
 
<ARTICLE> 5
<LEGEND>
THIS SCHEDULE CONTAINS SUMMARY FINANCIAL INFORMATION EXTRACTED FROM THE
UNAUDITED FINANCIAL STATEMENTS OF RENTAL SERVICE CORPORATION AS OF SEPTEMBER 30,
1998 AND 1997 AND FOR THE NINE MONTHS ENDED SEPTEMBER 30, 1998 AND 1997 AND IS
QUALIFIED IN ITS ENTIRETY BY REFERENCE TO SUCH FINANCIAL STATEMENTS.
</LEGEND>
<RESTATED>
<MULTIPLIER> 1,000
       
<S>                             <C>                     <C>
<PERIOD-TYPE>                   9-MOS                   9-MOS <F1>
<FISCAL-YEAR-END>                          DEC-31-1998             DEC-31-1997
<PERIOD-START>                             JAN-01-1998             JAN-01-1997
<PERIOD-END>                               SEP-30-1998             SEP-30-1997
<CASH>                                           7,702                   4,887
<SECURITIES>                                         0                       0
<RECEIVABLES>                                  121,409                  48,561
<ALLOWANCES>                                     4,934                   4,867
<INVENTORY>                                     46,780                  20,701
<CURRENT-ASSETS>                                     0                       0
<PP&E>                                         829,141                 312,567
<DEPRECIATION>                                 128,075                  52,033
<TOTAL-ASSETS>                               1,285,819                 462,577
<CURRENT-LIABILITIES>                                0                       0
<BONDS>                                        724,692                 224,535
<PREFERRED-MANDATORY>                                0                       0
<PREFERRED>                                          0                       0
<COMMON>                                           238                     149
<OTHER-SE>                                     406,299                 171,740
<TOTAL-LIABILITY-AND-EQUITY>                 1,285,819                 462,577
<SALES>                                        127,323                  60,783
<TOTAL-REVENUES>                               410,400                 172,332
<CGS>                                           97,244                  45,644
<TOTAL-COSTS>                                  300,169                 127,643
<OTHER-EXPENSES>                                36,461                  17,907
<LOSS-PROVISION>                                 2,934                   1,789
<INTEREST-EXPENSE>                              34,328                   8,863
<INCOME-PRETAX>                                 36,508                  16,130
<INCOME-TAX>                                    15,606                   7,172
<INCOME-CONTINUING>                             20,902                   8,958
<DISCONTINUED>                                       0                       0
<EXTRAORDINARY>                                      0                     534
<CHANGES>                                            0                       0
<NET-INCOME>                                    20,902                   8,424
<EPS-PRIMARY>                                      .99                     .65
<EPS-DILUTED>                                      .97                     .64
        
<FN>  
<F1>
The financial schedule for the nine months ended September 30, 1997 is restated
to conform its presentation to the requirements of FAS #128.
</FN>

</TABLE>