One hundred sixty-one patients with postoperative pain were treated at a single center in a double-blind, randomized, parallel study designed to compare the efficacy and safety of single oral doses of ketoprofen (50 and 150 mg), an acetaminophen (650 mg) plus codeine (60 mg) combination, and placebo. From 1 through 4 hours after administration of the study drugs, the mean summed pain intensity difference (SPID) and time-weighted total pain relief (TOPAR) scores for the three active treatments generally were significantly (P less than 0.05) higher than those for placebo but not significantly different from each other. At the 6-hour evaluation, the ketoprofen groups, but not the acetaminophen-codeine group, had higher (P less than 0.05) mean SPID and TOPAR scores than the placebo group, as a result of a shorter duration of pain relief in the acetaminophen-codeine group. The 6-hour TOPAR scores were significantly (P less than 0.05) higher for both ketoprofen groups than for the acetaminophen-codeine group; the ketoprofen 150 mg group also had significantly (P less than 0.05) higher mean 6-hour SPID and global subjective assessment scores. As a result of a higher frequency of somnolence, there was a significantly (P less than 0.05) greater incidence of central nervous system adverse drug reactions among patients treated with acetaminophen plus codeine than among those treated with 150 mg of ketoprofen. These results indicate that the analgesic efficacy of both 50 and 150 mg doses of ketoprofen equals that of acetaminophen 650 mg plus codeine 60 mg and the duration of the analgesic effect of ketoprofen is significantly longer.