STUDY OBJECTIVE: To compare postoperative morphine use, analgesic efficacy, and side effect profiles in patients following orthotopic liver transplantation (OLTx) and liver resection (LR). DESIGN: Retrospective study. SETTING: Liver transplant and liver resection surgery at a university hospital. PATIENTS: 25 ASA physical status I, II, III, and IV patients undergoing OLTx or liver resection. MEASUREMENTS AND MAIN RESULTS: Morphine use was significantly decreased in the OLTx patients at 6,12, 24, 48, and 72 hours following commencement of patient-controlled analgesia. After commencement of patient-controlled analgesia, pain scores were significantly reduced in the OLTx group compared with those in the liver resection group at 6 and 12 hours. CONCLUSIONS: Orthotopic liver transplant patients experienced less pain and used less morphine postoperatively than did liver resection patients.