A study on effects of lidocaine on auditory brainstem response(ABR) in tinnitus patients was performed to understand the mechanism of action of lidocaine in suppressing tinnitus and thus, the basic information on the pathophysiology of tinnitus. The results were as follows : 1) 15 patients(75%) showed suppression of tinnitus to intravenous lidocaine. 2) Before intravenous infusion of lidocaine, wave I latency was 1.61±0.24msec, wave V latency was 5.75±0.31msec and wave I-V interval latency was 4.14±0.17msec. 3) 5 minutes after intravenous infusion of lidocaine, wave I latency was prolonged by 0.10±0.14msec, wave V latency was prolonged by 0.38±0.19msec, and wave I-V interval latency was prolonged by 0.28±0.12msec(p<0.05). 4) 30 minutes after intravenous infusion of lidocaine, wave I latency was prolonged by 0.06±0.11msec, wave V latency was prolonged by 0.17±0.17msec, and wave I-V interval latency was 0.12±0.13msec(p<0.05). 5) 5 minutes after lidocaine infusion, wave I-V interval latency increased by 0.31±0.10msec in lidocaine responsive group and by 0.17±0.12msec in non-responsive group. These figures were statistically significant(p<0.05). As conclusion, it is suggestive that the action of lidocaine may be mediated by the prolongation of the central conduction time in auditory pathway.