To evaluate the cardiovascular effect of lidocaine and serum electrolytes during inhalational or intravenous anesthesia, thirty-two healthy patients were randomly divided into three groups and measured systolic pressure, diastolic pressure, mean pressure, heart rate and serum K+ and Na+ level were measured at 30 sec, l, 3, 6, 12 minutes after intravenous injection of lidocaine(1.5 mg/kg) during halothane-N2O-O2 or enflurane-N2O-O2 or diazepam-N2O-O2 anesthesia. In all 3 groups, the values of hemodynamic and serum electrolytes were not changed by 2% lidocaine. These results indicate that intravenous injection of lidocaine(1.5 mg/kg) to prevent undesirable reflexes and to prevent intracranial hypertension is a safe method without depression of hemodynamics.