The authors conducted a prospective randomised double-blind comparison of patient-controlled analgesia (PCA), with a combination of morphine and ketorolac versus morphine alone and ketorolac alone in the management of postoperative pain after orthopaedic surgery. Forty-two patients were randomly assigned to three groups. Group 1 was given 1 mg/ml morphine, group 2 was given 3 mg/ml ketorolac and group 3 half-doses of each. After a loading dose of 0.07 ml/kg, PCA was started at an initial setting of 1 ml per demand, with a 10-min lock-out interval and no background infusion. Pain was measured at rest and during movements for 48 h. The combination of morphine and ketorolac was more effective than morphine or ketorolac alone in relieving rest pain throughout the study. The combination was also more effective during movement than either drug alone, but only for the first 24 h. The consumption of morphine and ketorolac was significantly lower when the two drugs were administered together. The incidence of urinary retention was highest in the group given morphine alone. The combination of half-doses of morphine and ketorolac is more effective in controlling postoperative pain than either drug alone. This combination also reduces analgesic consumption and morphine-related adverse events.