Why anesthesiologists use the muscle relaxants? Because muscle relaxants are an adjunct to modem anesthesia practice today. What should be pepared whenever using a muscle relaxant? Of course, its necessary for artificial respiration. Why should be anesthesiologists monitor the neuromuscular blockade? There are so many factors affecting neuromuscular blockade. Factors are ; individual difference, age, sex, bady fluid, drug interactions including muscle relaxants themself and more than 250 drugs including anesthetics and antibiotics, disease states, hypothermia etc. That why anesthesiologists should know the degree of neuromuscular blockade. Whenever assurance on the degree of neuromuscular blockade is essential to the modern anesthetic practice. Observation of the motor response to peripheral nerve stimulation is helpful. Use of the peripheral nerve stimulator for monitoring of the neuromuscular blockade must be made mandatory whenever muscle relaxants are used. This study was performed 50 healthy patients. Ulnar nerve-adductor pollicis was stimulated simultaneously both hand by TOF and DBS3,3 each, during intubation dose of vecuronium 0.1 mg/kg and same stimulation was given both hand during anesthetic maintenance by intermittent bolus of vecuronium 1-2 mg during surgery. Number of twitch was counted by each TOF and DBS3,3 in the same time and onset time (TOF, TO) and time for reappearance of TOF, Tl was measured. Results were as follows ; 1) Simple, by use of peripheral nerve stimulator. 2) During onset time ; TOF twitch was disapperared earlier than DBS3,3. 3) During recovery phase ; DBS3,3 twitch was appeared earlier than TOF. 4) Onset time was 215.4+/-54.04 sec. and TOF, Tl reappearance was 1,793.4+/-487.61 sec. 5) Clinical evaluation of neuromuscular function was more reliable by number of twitch count with ulnar nerve-adductor pollicis on TOF than DBS3,3.