On account of its histamine releasing and ganglionic blocking properties tubocurarine is known to have significant hemodynamic effects. Methylation of the compound produces metocurine and should decrease both histamine release and ganglionic blockade. The hemodynamic effects of these two compounds were compared in 40 patients anesthetized with halothane, nitrous oxide, oxygen. These 40 patients were divided into two groups by administering tubocurarine or metocurine. Group I: When patients had no responses to surgical stimuli after induction, mean arterial blood pressure, pulse rate, pulse pressure were measured 1, 3, 5 min before administration of tubocurarine as control value. After administration of tubocurarine 0.51 mg/kg (ED), mean arterial blood pressure, pulse rate, pulse pressure were measured every minute for twenty minutes as experimental value. (n= 20) Group IL Metocurine 0,2S mg/kg (ED) was administered in the same way as the group I. (n=20) Result: Tubocurarine produced a decreaaed mean arterial blood pressure 22.9%, pulae pressure 16%, and an increaaed pulee rate 14.3%, 2 min after administration of drug(p<0.05). Also mean arterial blood pressure decreased for whole 20 min, pulse pressure for 7 min, and pulse rate increased for 4 min, significantly. But metocurine produced no significant hemodynamic effects. These data suggest that the hemodynamic margin of safety of metocurine is much grater than tubocurarine.