This study was taken to investigate by comparison with old muscle relaxantes and Vecuronium which is new non-depolarizing neuromuscular blocking agent, in clinical effects. The patients was composed of 40 healthy both sex adults who belong to class l or ll of ASA physical status. Vecuronium 0.08mg/kg(N=15), Succinylcholine 1mg/kg(N=10) and Pancuronium 0.08mg/kg(N=15) was injected independently when consciousness was lost after induction of thiopental sodium and immediately low concentration of enflurane with 50% N2O was inhaled by positive pressure ventilation. The degree of neuromuscular transmission was measure using the train of four stimulation of the ulnar nerve repeated every 20 second and the time was checked when the first twitch height(T1) was depressed to 85%, 75%, 50% and 25% and When T1 was recovered to 25%, 50% and 75% after administration of three muscle relaxants respectively. The results were as follows: 1) There were not a significant difference in Arterial blood pressure. Pulse, and serum electrolytes(Na+, K+) before and after vecuronium injection. 2) The onset times when T1 was reduced grom 100% normal height to 85, 75, 50 and 25% after administration of three muscle relaxants respectively, were 24+/-14.5, 28+/-10.3, 46+/-9.7, and 54+/-13.5 seconds in succinylcholine. 33+/-14.5, 55+/-22.0, 83+/-21.2, and 115+/-22.2 seconds in vecuronium, and 61+/-24.5, 79+/-25.3, 112+/-22.4, and 188+/-25.1 seconds in pancuronium. 3) In the recovery times when T1 was recovered to 25, 50 and 75% without anticholinesterase after administration of three muscle relaxants respectively, these were 7.3+/-1.37, 9.2+/-1.54, and 13.6+/-1.99, minutes in succinylcholine, 24.0+/-6.7, 31.0+/-9.9 and 45.0+/-17.8 minutes in vecuronium, and 89.0+/-27.0, 115.0+/-28.2 and 144.0+/-38.6 minutes in pancuronium. Recovery index which is the time from 25% to 75% recovery as a parameter of the speed of recovery was 20.27+/-12.60 minutes in vecuronium with comparison of 66.0+/-39.88 minutes in pancuronium. The onset and recovery time of vecuronium was faster than pancurosium, but later than succinylcholine, and endotracheal intubation was easily done without any difficulties in all cases at 50% depression of T1 when was on 83+/-21.2 seconds after vecuronium injection. 4) Average minute volume of respiration was 7.1+/-0.73l/min. and the time of head lift was 11.45+/-8.87 seconds at 75% recovery of T2 after vecuronium without any reversal agents, and at this 75% recovery of T1, T4 was recovered to 64.3+/-3.27%.