Patients (n - 120) undergoing major orthopedic (e.g.. total hip replacement). urologic (e.g.. radical prostatectomy), or gynecologic (e.g.. total abdominal hysterectomy) procedures were randomly assigned to receive either morphine or oxymorphone postoperatively using a patient-controlled analgesic (PCA) delivery system. The opioid analgesic was administered either intravenously (IV-PCA) or subcutaneously (SQ-PCA) during the 72-h study period. Oxymorphone. 0.6? /Mp 0.42 mg/h (0–24 h). 0.53 /Mp 0.35 mg/h (24–48 h),'and 0.42 /Mp 0.31 mg/h (48–72 h), was as effective as morphine. 2.2 /Mp 1.6 mg/h (0–24 h), 1.6 /Mp 1.2 mg/h (24–48 h), and 1.2 /Mp 1.1 mg/h (48–72 h), in providing postoperative pain relief (mean values /Mp SD). Although the average opioid dosage requirements were 10 to 28/X% higher with SQ-PCA. it is an acceptable alternative to conventional IV-PCA for pain control after major surgical procedures. Postoperative analgesia scores and patient satisfaction were similar in all four PCA treatment groups. Thus. SQ-PCA with either o.xymorphone or morphine represents a clinically acceptable alternative to IV-PCA in the treatment of postoperative pain.