The nucleus tractus solitarii (NTS), the primary sensory relay for gustatory and visceral afferent information conveyed mainly in vagal and glossopharyngeal nerves, has long been considered to contain only sensory neurons which were thought to function as threshold elements and to process afferent impulses by simple mechanisms of summation. In the case of deglutition, however, most of the data already published show that NTS neurons undoubtedly play a major role in generating the motor activity. Concerning the results on the localization of NTS swallowing neurons, most of the data were obtained before the different cytoarchitectonic subdivisions of the nucleus were reported from anatomical studies. The central mechanisms which generate the bursting activity of NTS swallowing neurons and their sequential or rhythmic firing are unknown. Extracellular recordings from neurons in the rat NTS region, where swallowing neurons are located, have shown that repetitive stimulation of afferent fibers within the tractus solitarius can elicit bursting discharges in some NTS neurons.