Sixty patients were randomly assigned to two equal groups. Group I received epidural morphine 1 mg after surgery and used a patient-controlled analgesia device programmed to deliver morphine 0.2 mg h−1, 0.2 mg per bolus. Group II received an epidural loading dose of morphine 1 mg plus ketamine 5 mg and used a patient-controlled analgesia device programmed to deliver morphine 0.2 mg+ketamine 0.5 mg h−1, morphine 0.2 mg+ketamine 0.5 mg per bolus with a lockout time of 10 min. The mean morphine consumption was 8.6±0.7 mg for group I and 6.2±0.2 mg for group II. Although group II utilized significantly less morphine (P<0.05), pain relief was significantly better in group II than in group I (P<0.05) in the first 3 h. Vomiting occurred more frequently in group I (26%) than in group II (13%). The frequency and severity of pruritus and level of sedation were similar in the two groups. These findings suggest that patient-controlled epidural analgesia with morphine plus ketamine may provide effective analgesia with a lesser dose of morphine and fewer subsequent side effects, compared with patient-controlled epidural analgesia with morphine alone after lower abdominal surgery.