In rat and guinea pig, cochlear efferents to the two ears were labeled simultaneously with different fluorescent tracers. It was found that in both species only few (1-3%) olivo-cochlear neurons were double-labeled and project to both cochleae. In most periolivary regions large olivocochlear neurons (OCN) projecting to the ipsilateral and contralateral side are intermingled and form a continuous cell column between the facial nucleus and lateral lemniscus. In a second series of experiments in rat, cochlear efferents and ascending olivo-collicular neurons were labeled. Olivo-cochlear and olivo-collicular neurons are intermingled in the lateral superior olive (LSO) and in the ventromedial periolivary region. No double-labeled neurons were found that project to the cochlea and the inferior colliculus.