Temporary latency shifts in auditory evoked potentials by intravenous injection of lidocaine were investigated in albino rats. Auditory brainstem responses (ABR) were recorded with 4000Hz short tone bursts. There was no significant difference of latencies in wave Pl of the ABR between drug-administered group (6 mg/kg body weight of lidocaine) and control group (0.6 ml/kg of 0.9% saline). As for waves P2. P3 and P4 of ABR, the latencies of the waves were significantly prolonged after the lidocaine injection (p < 0.05. U-test). The prolongation of latency of wave P4 was the most prominent in the fast waves and dependent on the dose of lidocaine. The latencies of the slow positive wave of the evoked potentials on the inferior colliculus (wave S) with clicks and the slow positive wave (wave P) and the negative wave following ABR (wave NA) with 4000Hz short tone bursts were also studied. The latencies of waves S. P and NA showed significant temporal prolongation (p < 0.05, U-test) after lidocaine injection. The present study revealed that a relatively small dose of lidocaine can cause temporary prolongation of latencies of auditory evoked potentials not only in the fast components but also in the slow components including wave NA which is a large slow negative wave following the ABR. The effects are considered to be caused by the action of lidocaine which reduces the excitabilities on the auditory nervous system.