Background : Recently, it was reported that bupivacaine-induced spinal block significantly reduced the hypnotic requirements for thiopentone, midazolam and propofol. We evaluated the hypnotic effect and requirements for intravenous propofol when pretreated with intravenous lidocaine. Methods : Fifty patients, ASA I or II, undergoing minor surgical procedures were randomly divided into five groups according to anesthetic pretreatment (group N: 0.9% normal saline; group 0.5: lidocaine 0.5 mg/kg; group 1.0: lidocaine 1.0 mg/kg; group 1.5: lidocaine 1.5 mg/kg; group 2.0 lidocaine 2.0 mg/kg). Ninty seconds after the administration of normal saline or lidocaine, propofol was administered intravenously over 5 sec in bolus doses of 0.2 mg/kg every 30 sec. The inability of patients respond to a simple command ("Open your eyes," said twice) was used as the end point for hypnosis. Responses to verbal commands were evaluated 25 sec after each bolus. The total dose required to achieve complete loss of response in each patient was recorded in mg/kg. The time of the loss of response was from the adminstration of propofol to the loss of response. Mean arterial pressures and heart rates were measured before induction, after loss of response, and immediately after induction. Results: The time and total dose required to achieve loss of response was significantly reduced in groups 1.0, 1.5 and 2.0. Heart rates in groups 2.0 and mean arterial pressure in groups 0.5, 1.0, 1.5, 2.0 were significantly decreased after the loss of response. Conclusions : We suggest that lidocaine pretreatment significantly enhances the hypnotic effect and reduces the dose requirement for propofol during the induction period. (Korean J Anesthesiol 1999; 37: 382∼386)