The lateral bulbar reticular formation of anesthetized rats was explored with microelectrodes in order to compare the response and field characteristics of its somatosensory cells with properties of units located in the adjacent spinal trigeminal complex. Responses were evoked in the cells using natural and electrical stimulation of the skin. Neurons in the reticular nuclei tended to exhibit long latencies, low following capacities and large receptive fields. On the other hand, trigeminal complex cells generally revealed opposite characteristics, more typical of primary sensory structures, such as short latencies, high following capacities and punctate-to-small fields. The distinction between the regions was emphasized by additional qualities which were peculiar to the reticular neurons: Bilateral peripheral representation, inhibition of on-going activity by means of peripheral stimulation and specific sensitivity to very coarse mechanical stimulation. In many respects, the data indicate that the Iateral reticular formation is intimately involved in the mediation of facial pain. They also support the view that it participates in this function by regulating the flow of nocioceptive activity from receptive mechanisms of the skin to the lemniscal pathways.