In a double-blind, placebo-controlled clinical trial (power of 80% to detect a 30% reduction in morphine consumption, P < 0.05), we have determined that the administration of two doses of intravenous ketoprofen 100 mg, one at the end of surgery and the second 12 hours postoperatively, was associated with a significant reduction in morphine consumption at eight (P = 0.028), 12 (P = 0.013) and 24 hours (P = 0.013) but not four hours (P = 0.065) postoperatively, as compared to placebo, when assessed by patient-controlled analgesia. There was no difference between the groups in pain scores or in the incidence of nausea and vomiting. One patient in the placebo group suffered from excessive sedation while one patient from the ketoprofen group suffered from transient oliguric renal failure. There were no other adverse effects. The results of this study show that ketoprofen does provide a morphine-sparing effect in the management of postoperative pain after abdominal surgery.