The human average evoked response to clicks, recorded from almost any position on the scalp, shows a characteristic short-latency component with its peak at 30 msec. These responses are probably composite, originating partly from muscle and partly from brain. The response recorded from parietal (Pl) to vertex (Cz) differs significantly from a known muscular response from the inion. The 30-msec component from inion is markedly enhanced by contraction of the posterior neck muscles, while that from Pl-Cz is little affected. The two responses differ in their relations of amplitude to stimulus intensity. The Pl-Cz response also differs from temporalis and frontalis muscle responses. muscle response to clicks; sources of evoked responses Submitted on October 15, 1964