A study was conducted to compare the analgesic activity of single oral doses of etodolac (25, 50, 100, 200, and 400 mg) with 650 mg aspirin and placebo. A total of 146 patients with moderate or severe pain from orthopedic or urologic interventions received one of the test medications 13-25 h after the beginning of surgery and according to a randomized allocation balanced as to initial pain intensity. Data for pain intensity and pain relief were collected at 1/2 h and then hourly for 8 h. Vital signs and adverse reactions were also recorded. One hundred and forty-two patients completed the study: four were excluded because of protocol deviations. The average response to 100, 200, and 400 mg of etodolac was superior to that of placebo. On the basis of SPID, TOTPAR, and duration of analgesia, 400 mg etodolac was also significantly more effective than 650 mg aspirin. Mild side effects probably or possibly related to etodolac were reported by three patients. This study provides evidence that etodolac in doses of 100 mg and higher is an effective and well-tolerated analgesic.