This double-blind study evaluates whether ketamine given epidurally is effective for postoperative pain relief, and compares the effects of epidural ketamine with those of epidural morphine. Sixty-eight patients undergoing abdominal gynecologic surgery were randomly assigned into six groups (control; ketamine 4, 6, and 8 mg in saline; 6 mg in 10% glucose; morphine 3 mg). All patients were anesthetized with thiopental, nitrous oxide, and enflurane, and drugs were administered epidurally at the end of the operation. The duration of analgesia in the ketamine groups did not differ from that in control patients and the difference in diluent had no observable effects. Significantly, none of the patients in the morphine group needed additional analgesics within 24 hr, whereas 85% in the other five groups did. We conclude that ketamine administered epidurally is inadequate for postoperative pain relief after gynecologic operations.