To determine if deafferentation plays a role in the development of epileptiform-like activity in subcortical structures. Eleven cats have undergone successful retrogasserian trigeminal rhizotomy to date. Two normal cats have been studied to provide control responses. Neurons of the normal spinal trigeminal nucleus were found to have low spontaneous rates and strong evoked responses from the appropriate receptive fields. Latency to skin stimulation in n. interpolaris or caudalis ranged from 2-5 msec. Neurons were inhibited by GABA, B-alanine, and glycine. Neurons were excited by glutamate and d,l-homocysteic acid.