The relationship between the activity of the inferior colliculus and each component of the auditory brain stem response (ABR) was investigated in rats using an electrical coagulation method. The ABR seems to be a composite of slow and fast waves, and the central nucleus of the inferior colliculus is more important for the slow wave than for the fast waves. There was little effect on the shape and latency of the fast waves of the ABR when the destruction was limited to the central nucleus. When the lesion was extended to or located in the lateroventral part of the inferior colliculus, where the nerve fibers of the lateral lemniscus penetrate into the inferior colliculus, potentials 5 and 6 were abolished, but potential 4 remained with a slightly prolonged latency. These findings suggest that the structures peripheral to the inferior colliculus play an important role for the generation of potential 4, and the inferior colliculus, particularly its lateroventral part, is essential for generation of potentials 5 and 6.