The bilateral efferent supply to the inner ear receptor fields is located in the hindbrain. In ovo injections of Dil into the common facial/vestibulo-acoustic nerve root at 3 days of chick development (stage 16) followed by analysis at 7 days has revealed the origin of the contralateral efferent neurons of the inner ear and their relation to the transient hindbrain rhombomeres. These neurons have a rhombomere 4-specific origin and form their commissure not by axonal outgrowth but, unusually, by transmedian cell migration into the contralateral rhombomere 4 and rhombomere 5. Neurons first project their axons from the ipsilateral basal plate through the VII/VIIIth nerve exit point and then migrate in the opposite direction, crossing the floor plate at stage 19-21. This rhombomere-specific cell behavior provides evidence at the cellular level that segmentation is intimately involved in establishing the pattern of this region of the CNS.