The effect of moderate hypotensive anesthesia on blood loss, need for transfusion, and length of surgery of forty-nine patients who underwent posterior spinal fusion and Harrington-rod instrumentation was compared retrospectively. Twenty-seven patients were given enflurane as the main anesthetic agent, with fentanyl supplementation, and their blood pressure was maintained at twenty to thirty millimeters of mercury less than the preoperative systolic blood pressure. These patients were compared with twenty-two patients who had been anesthetized with nitrous oxide, oxygen, and narcotic technique and were normotensive throughout the duration of the anesthesia. The results were analyzed by the unpaired Student t test. Moderate hypotensive anesthesia was found to significantly decrease the average blood loss by nearly 40 per cent, reduce the need for transfusion by nearly 45 per cent, and shorten the average operating time by nearly 10 per cent. No complications attributable to the anesthetic technique occurred. The findings of this study suggest that moderate hypotensive anesthesia with enflurane and fentanyl supplementation may be of benefit in scoliosis surgery by reducing blood loss, the need for blood replacement, and operating time.