Objective: To compare the effectiveness of intravenous patient-controlled (IV-PCA) ketorolac to IV-PCA morphine in the treatment of postoperative pain in cancer patients. Design: In a double-blind, prospective, randomized trial, patients received either morphine in 1 mg/ml concentration or ketorolac 5 mg/ml for postoperative pain control. On arrival to the postanesthesia care unit (PACU), the patients received 2 ml of medication every 5 min, until satisfactory analgesia was achieved. If pain persisted after 20 ml of study drug had been administered, 0.1 mg/kg morphine was given IM. On discharge from the PACU, the patients were placed on an IV-PCA pump. All patients received a basal infusion of 1 ml/h with a 1-ml on-demand bolus and a lockout interval of 10 min. Patients were offered 0.1 mg/kg morphine IM every 6 h, which they could refuse. Setting: University Cancer Center. Patients: Seventy patients scheduled for abdominal or truncal cancer operations. Main Outcome Measures: Visual analog pain scores (VAPS) and Visual analog sedation scores (VASS) were used to measure the quality of pain control achieved either with ketorolac or morphine. The incidence of side effects was documented. Results: The VAPS were comparable between the groups. Patients in the ketorolac group requested more supplemental IM morphine. However, the total morphine dose and incidence of side effects was significantly higher in patients receiving IV-PCA morphine. Conclusions: These results indicate that ketorolac supplemented with small doses of morphine is associated with a lower incidence of nausea, vomiting, and pruritus compared to morphine alone. This combination should be considered where immunosuppression from operation and adminstration of morphine is undesirable.