The authors studied the priming effects of the nondepolarizing neuromuscular blockers on the frequency of discomfort, intubation condition and the time interval between the administration of nondepolarizing neuromuscular blockers and endotracheal intubation. Thirty two patients were divided randomly into four groups: the patients administered vecuronium priming dose, 0.02mg/kg and intubating dose, 0.06mg/kg (Group I), vecuronium customary single dose, 0.1 mg/kg (Group II), pancuronium priming dose, 0.02 mg/kg and intubation dose, 0.06mg/kg (group III) and pancurnium customary single dose, 0.1 mg/kg (group IV). The results were as follows. 1) Seven patients complained discomfort after administration of priming dose in the priming groups. (Group I and III) 2) There was better intubating condition in the priming groups than the customary single dose groups. 3) The time intervals between the administration of intubating dose and the maximum depression of single twitch response were revealed 57.9±14.6 seconds, 115.5±27.2 seconds, 74.5±30.0 seconds and 101.4±13. 7 seconds in I, II, III and IV group respectively. The time interval in group I was significantly shorter than group II (p< 0.05). And the interval in group III was also significantly shorter than group IV (p<0.05). With the above results we conclude that the priming groups provide smooth and rapid intubation condition than the customary single dose group, in spite of small total intubating dose.