The effect of alcuronium given before succinylcholine (SCh) on plasma catecholamine concentrations, systolic blood pressure and heart rate was studied in patients anesthetized with enflurane. Twenty-one patients were divided into three groups; six control patients without SCh, eight SCh (1 mg/kg) patients, and seven pretreated patients given alcuronium, 0.04 mg/kg, 5 min before SCh, 1 mg/kg. In the SCh group, mean plasma norepinephrine concentrations, systolic blood pressure, and heart rate significantly increased with onset of fasciculations, whereas in the pretreated patients these variables did not change significantly and no fasciculation was observed. These results indicate that alcuronium pretreatment significantly attenuates the SCh-induced increases in plasma norepinephrine concentrations, systolic blood pressure and heart rate.