The ascending and descending pathways from the inferior colliculus were studied in the kangaroo rat (Dipodomys merriami) using aspiration or electro-lesioning techniques. The ipsilateral ascending projections were traced to the parabrachial region, the interstitial nucleus, the pars principalis and pars magnocellularis of the medial geniculate and the medial and lateral posterior thalamic nuclei. A projection to the deep layers of the superior colliculus leaves medially from the ipsilateral brachium of the inferior colliculus.Smaller, contralateral projections were traced to the dorsomedial portion of the central nucleus of the inferior colliculus, the parabrachial region, the medial posterior thalamic nuclei and the rostral four-fifths of the medial geniculate body. No fibers were traced to the caudal portion of the medial geniculate, or to the contralateral lateral posterior thalamic nuclei.The descending projections were traced ipsilaterally to the periaqueductal gray, the dorsal and ventral nuclei of the lateral lemniscus, the lateral pontine nuclei, the nucleus of the trapezoid body, and both the ipsilateral and contralateral dorsal cochlear nuclei.