The purpose of this study was to evaluate the analgesic efficacy and adverse effect liability of single oral doses of indoprofen, 50 mg, 100 mg, and 200 mg, compared with aspirin, 300 mg and 600 mg, and placebo in the relief of moderate to severe postpartum pain. Two hundred-ten patients entered a randomized, double-blind, parallel group study and were evaluated over a six-hour period by a single nurse-observer. There was a significant imbalance in the distribution of pain types across treatments that compromises the interpretation of the results. In addition to analyzing the data from all patients, the subsets with episiotomy/cesarean section pain and uterine cramp pain were examined separately. The latter group had too few patients to permit distinction between drugs. The 100 mg and 200 mg doses of indoprofen were significantly (P less than or equal to .05) more effective than placebo for many variables including the following summary values: sum of pain intensity difference (SPID), sum of hourly relief values (TOTPAR), and % SPID for all patients as well as in the subset of patients with episiotomy/cesarean section pain. Aspirin, 600 mg, was also significantly more effective than placebo for many of the same measures of analgesia in the episiotomy/cesarean section subset. Pairwise differences were also seen between placebo and aspirin, 300 mg, but on fewer variables. Indoprofen, 100 mg, was significantly more effective than aspirin, 600 mg, at hour 6 for pain intensity difference (PID) in the episiotomy/cesarean section subset. The effect of indoprofen appeared to plateau above 100 mg.(ABSTRACT TRUNCATED AT 250 WORDS)