Succinylcholine(SCh)-induced muscle fasciculations may be prevented by pretreatment with small doses of nondepolarizing muscle relaxants. The optimal timing of pretreatment to abolish fasciculation varies according to the drug used and dose. In this study, we determined the optimal timing of pretreatment of pancuronium to prevent muscular fasciculation in 100 patients. Each group (n=20) was received pancuronium 0.015 mg/kg at 1, 2, 3, 4, 5 minutes before SCh 3 mg/kg administration, respectively. The degree of fasciculations after SCh administration was observed and classified into one of 4 grade. There were significant differences between each groups (Ridit scores=10.078, p<0.01) To compare observed fasciculations of one grpup with those of the others, the degree of fasciculations was summed according to an arbitrary scale. The summation of grade in 4 minute group was lowest in this scale. It was concluded that the optimal timing of pretreatment, pancuronium 0.015 mg/kg, was 4 minutes before SCh 3 mg/kg injection.