Auditory brain stem response (ABR) was investigated in shiverer mice and reeler mice. In shiverer mice, the wave latency after ABR wave III was prolonged and wave V disappeared. Although the interpeak latencies were also prolonged, there were some differences according to the site of the disorder. The threshold was found to be normal. In reeler mice, the findings on the wave latencies were inconsistent. Some of the mice showed no differences from the controls, some showed prolonged latencies, and some showed only wave I. The ABR findings on the shiverer mice were considered to be due to abnormal or poor myelin formation in the central nervous system. Abnormal ABR findings in the reeler mice are probably caused by a secondary change due to the abnormal cell positions resulting from mutation.