The individual onset of action of pancuronium and vecuronium has been examined with a priming dose of same or the other agent or two times priming. Measurement of changes in the Tl% of TOF ratio of the adductor pollicis muscle were performed by Accelograph (Biometer). Sixty adult patients were administered Vecuronium(V) 0.015mg/kg (group 1), V 0.005mg/kg 3 minutes after 0.01mg/ kg(group 2), Pancuronium(P) 0. 015 mg/kg(group 3,4) as a priming agents. After 5 minutes, the intubating dose of V 0.085mg/kg (group 1,2,3), P 0.085 mg/kg (group 4) were administered with the induction agent, thiopental sodium 5 mg/kg. All sixty patients underwent orotracheal intubation at 60 seconds after the injection of intubating dose. Intubation condition, reduction of Tl% at 60 seconds, the onset time of maximal blockade (Tl 0%) were evaluated. There was no difficulty in intubation. Fifty-two (86%) patients were distributed in exellent and satisfactory grade of largest in group 2. While group 3 showed more rapid than group 4, group 2 showed the most rapid onset time significantly. These results indicate that the twicely divided dose of vecuronium for priming agent may be adequate and vecuronium after priming with pancuronium is more rapid than priming with same agent.