BACKGROUND: Priming significantly shortened the onset of neuromuscular blockade(NMB), but also results in a high incidence of side effects. This study was designed to determine the effect of infusion priming method on the side effects, intubation condition, and onset of NMB compared with divided priming method. METHOD: The effects of different priming method of vecuronium on onset time and endotracheal intubation condition were investigated. 40 patients were studied in two parts. In control part, 20 patients were allocated into two groups(n=10 in each group) receving 10, 20 g/kg vecuronium as a priming dose, followed by a intubating dose(0.1 mg/kg-priming dose) 3 min later; the other part, 20 patients were allocated into two groups(n=10 in each group) receving 0.2 mg/kg/hr vecuronium continuous intravenous infusion, followed by a intubating dose(0.1 mg/kg-total infusion dose) 3, 5 min later. Onset time is calculated by single twitch stimulation test from injection of the intubating dose to maximum depression of the single twitch. Intubatin condition was appreciated based on vocal cord reflex, coughing, and jaw relaxation and scored. RESULTS: The times to fade out on the single twitch of the intravenous infusion priming group were shorter than control priming group. There was no difference between control priming group and infusion priming group to evaluate the intubation conditions. Side effects in the continuous infusion group were lesser than control priming group. CONCLUSION: This results suggest that the use of continuous infusion method is one of the promising methods to shorten the neuromuscular blockade and to provide more comfort to the patients.