The purpose of this study was to compare postoperative analgesic effect according to intravenous doses of ketorolac. The ninety-eight adult patients, scheduled for elective surgery under general anesthesia, were randomly assigned to receive saline or one of the five doses of ketorolac (10, 15, 30, 45, 60mg). After recoverg from anesthesia, saline or ketorolac was injected intravenously, and the visual analogue score, sedation secore, mean blood pressure, heart rate, and the incidence of nausea and vomiting were measured 30 minutes, 1 hour and 2 hours the injection. Saline or 10 mg of ketorolac had no postanalgesic effect. Above 15 mg of ketorolac had analgesic effect, but this analgesic effect was not increased with increasing doses of ketorolac (30, 45, 60 mg). Any side effects (nausea, vomiting, excessive sedation, cardiopulmonary depression, and renal and hematologic adverse events) was not observed associated with ketorolac administration. These results suggested that 15 mg of ketorolac is the most reliable dose for postoperative anlgesia in intravenous administration.