We mapped the topographic distribution of auditory responses in the posterior cerebellar vermis of the cat under barbiturate anesthesia. Auditory neurons in the granule cell layer of lobules VI and VII appeared to be arranged in columns perpendicular to the surface of the cerebellar cell layers. Mapping the surface of the cerebellum, auditory responses were found as separated patches of the order of a square millimeter. Neurons on these patches responded to auditory stimuli but neurons between patches did not respond to sound. In decerebrated cats, the entire granule cell layer within the cerebellar auditory area responded to acoustic stimulation without a patchy pattern. Responses to tonal stimuli from single neurons in the granule cell layer were studied before and after the induction of barbiturate anesthesia. Some neurons showed no change in their responses to sound before and under barbiturate. But other neurons showed dramatically attenuated responses or essentially stopped responding as a result of barbiturate anesthesia. These results suggest that there may be two types of granule cells distinguishable in their auditory responses and therefore possibly in function.