Lesions in the rignt (?) colliculus were made in 8 albino rats and the efferent projections were studied by Nauta's technique with the following results:Ipsilateral projections: The overwhelming majority of the degenerating fibers runs by way of the inferior quadrigeminal brachium, a small part of which terminating in the reticular nucleus of the lateral tegmentum of the midbrain and the major part of which terminating in the magnocellular and the parvicellular divisions of the medial geniculate body. A smaller nunber of the degenerating fibers terminate via the tecto-pontine tract in the lateral pontine nucleus. A few degenerating fibers terminate in the central gray of the midbrain and the deep stratum of the superior colliculus.Contralateral projections; With the exception of some feed-back fibers all contralateral projections pass through the commissure of the inferior colliculus. The majority of the degenerating fibers terminate in the dorsal region of the contralateral inferior colliculus. A minor part of the degenerating fibers run by way of the inferior quadrigeminal brachium to terminate in the reticular nucleus of the lateral tegmentum of the midbrain.Feed-back fibers: The feed back fibers are derived from the inferior colliculus and descend in the lateral lemniscus. As they reach the level of the superior olivary complex they divid into two parts: One part passes through the pyramidal tract of both side and terminates in the contralateral trapezoid ventral nucleus, dorsal cochlear nucleus and ventral cochlear nucleus. The other part terminates in the same nuclei ipsilaterally.Based on the observations mentioned above, the impression were obtained that the efferent fibers of the inferior colliculus mostly terminate in the ipsilateral medial geniculate body and the contralateral inferior collicuhs, through the latter impulses may reach the controlateral medial geniculate body indirectly. The inferior colliculus in the albino rat is considered as Woollard et al ('40) put in cat and guinea-pig, "The midbrain auditory nudei subserve very few reflex activities, being almost wholly sensory centres."