The analgesic effects of single intravenous doses of alpha-methyl-4-(2-thienyl-carbonyl)phenylacetic acid (suprofen, Suprol) 200 mg/ml and alpha-4-(2-isoindolinyl-2-one)-phenylpropionic acid (indoprofen) 200 mg were compared within the scope of a randomized single-blind study. The test population consisted of 87 patients for whom analgesic treatment was indicated as soon as severe to major pain set in following meniscectomy or disease of a ligament. The treatment groups were homogeneous with respect to demographic data and intensity of pain prior to treatment. In the pain models chosen both drugs resulted in rapid pain relief within 15 min following their application. As to decreased intensity of pain (SPID) and pain relief (TOTPAR), the results obtained 2 h after the test were with indoprofen statistically significantly superior to those obtained with suprofen. The investigator's global appreciation of effectiveness revealed no intergroup differences. Therapeutic results were seen in 95.5% of the subjects on suprofen and in 97.6% of those on indoprofen. The tolerability of suprofen was very good in 95.3% of the cases on suprofen and in 97.3% of those on indoprofen. Four patients in the suprofen group experienced adverse reactions that were, however, not drug related.