An experimental study for the effects of lidocaine and anticonvulsants, carbamazepine and primidone, on auditory brainstem responses(ABR) in rabbits was performed to understand the mechanisms of the action of these drugs in tinnitus and the basic information of the pathophysiology of tinnitus. 1) After intravenous infusion of lidocaine, 2.0 mg/min for 60 minutes, the latencies of ABR waves were prolonged immediately and gradually returned to normal in 90-180 minutes. 2) After oral administration of carbamazepine, 200 mg/kg, the latencies of ABR waves were prolonged maximally in 4-7 hours and gradually returned to normal in 8-14 hours after administration. 3) The interpeak latency of wave I-V was prolonged remarkably, compared with the latency of wave I, in both groups. 4) There was no change of ABR patterns after oral administration of primidone, 250 mg/kg, in 16 hours. As a conclusion, prolongation of all wave latencies in ABR was observed with lidocaine and carbamazepine, but no change with primidone in rabbits. And it is suggested that the principal effect of lidocaine and carbamazepine might be the prolongation of the central conduction time in auditory pathway.