Experiments were performed to anatomically and electrophysiologically demonstrate the existence of a dentato-reticulospinal pathway in the cat. Reticulospinal neurons projecting to the lumbar region of the spinal cord were shown to respond to stimulation in the dentate nucleus at latencies as short as 0.8 ms. The latency of these responses could be varied by changing either stimulus strength or stimulus frequency. Furthermore, intracellular recordings revealed that these responses were associated with a graded depolarization with latencies as short as 0.8 ms. Collision experiments confirmed that the responses recorded in reticular neurons following spinal cord stimulation were antidromically evoked and that the orthodromically evoked responses to dentate stimulation were conducted to the spinal cord. To ensure that the short latency responses evoked in these cells by dentate stimulation were not the result of activating a cerebellar projection to the brainstem through the inferior cerebellar peduncle, an experiment was performed demonstrating that these responses could be blocked by lesions of the brachium conjunctivum. In the anatomical experiments, small injections of horseradish peroxidase limited to the rostromedial region of the medullary reticular formation resulted in the retrograde labeling of neurons in the contralateral dentate nucleus. On the basis of these electrophysiological and neuroanatomical findings, it was concluded that a dentatoreticulospinal system is present in the cat. a system by which the dentate nucleus may affect neuronal integration occurring in the spinal cord.