Enflurane, and isoflurane potentiated for the vecuronium-induced neuromuscular blokade in a study of 30 patients anesthetized with 1.0 or 1.5 MAC enflurane, and isoflurane or ketaminefentanyl. In the patients anesthetized with 1.0 MAC isoflurane or enflurane, 50% nitous oxide was administrated simultaneously. The median effective dose of vecuronium m the ketamine-fentanyl anesthesia patients(34,0±1.2 ug/kg) was higher than that in the 1.0 and 1.5 MAC enflurane or isoflurane patients(2l.2±3.2 and 19.4±2.7, or 17.8±4.5 and 20.0±5.3 ug/kg, respectively). There is no significant difference in ED 50 and ED 95 between 1.0 and 1.5 MAC with enflurane or isoflurane. The duration in patients with enflurane was longer than that in the other groups. But, there is no difference in recovery indices among all the groups. The authors conclude that enflurane or isoflurane potentiantes the vecuronium-induced neuromuscular blockade comparing with ketamine-fentanyl anesthesia. Enflurane prolongs the duration of vecuronium in contrast to isoflurane. But, there is no significant difference between 1.0 and 1.5 MAC in same anesthetic considered usually as clinical anesthetic depth.