This study was performed to examine the influence of lidocaine HCl on evoked otoacoustic emissions (EOAE) in tinnitus case. EOAE were recorded before and after intravenous injection of lidocaine HCl in 19 patients with unilateral tinnitus. EOAE amplitudes were significantly increased after injection of lidocaine HCl for 10 minutes. Between the effective group and the non-effective group of lidocaine HCl for tinnitus, significant differences were recognized after injection of lidocaine HCl for 10 minutes. These results suggested that lidocaine HCl stimulated cochlear mechanics. Significant differences were not recognized at any time between the group of hearing loss with unknown origin, the group of Meniere's disease and the group of tinnitus without hearing loss.