Vestibular-nerve fibers, even those innervating a single end organ, have been found to differ in their branching patterns within the neuroepithelium. They also vary in their responses to head movements and to activation of efferent fibers, and in the central pathways to which they contribute. These results are enabling plausible inferences to be made about the peripheral mechanisms determining the discharge properties of physiologically distinguishable afferents, and about the contributions the different afferents make to the overall functioning of the vestibular system.