Introduction Since its original demonstration in the cat by the classical neuroanatomical studies of Rasmussen,1,2 the efferent cochlear bundle has been described in forms as low on the phylogenetic scale as the alligator and pigeon3 and as high as the monkey.1 All of these forms, having such efferent systems, possess certain anatomical structures related to the origin and course of this bundle which remain constant—that is, a superior olive, a decussating midline bundle beneath the floor of the fourth ventricle between the facial genua, a vestibulocochlear (Oört) anastomosis, and an intraganglionic spiral bundle in the cochlea. Since man fulfills all of these anatomical requirements, it has been presumed that he also possesses an efferent cochlear bundle of Rasmussen. However, direct evidence to support this presumption has not to date been offered. It is the purpose of this paper to present such direct evidence and, furthermore, to describe