To test the hypothesis that the postoperative abdominal pain of tubal occlusion is mediated by prostaglandins, the effects of meclofenamate, an analgesic and a potent inhibitor of cyclooxygenase, on postoperative analgesia and incidence of abdominal pain were compared with those of acetaminophen, a weak inhigitor of prostaglandin activity. 100 patients undergoing tubal occlusion under local anesthesia in a Kentucky health facility were studied. Tge patients were randomly divided into 4 equal groups: 1) control; 2) acetaminophen, 1300 mg; 3) meclofenamate, 100 mg; 4) meclofenamate, 200 mg. The fallopian tubes were occluded by electrocautery in 47 patients and by application of Falope rings in 53 patients. Both acetaminophen and meclofenamate provided substantial analgesia for 4 hours after the operation (p0.05). Meclofenamate reduced the incidence of abdominal pain by 1/2 (p0.02), but acetaminophen did not. These results suggest that a portion of pain relief achieved by meclofenamate may be due to suppression of myosalpingian and/or myometrial contractions, a process mediated by prostaglandins.