The effects of innocuous and noxious mechanical stimulation of skin, and of baroreceptor and chemoreceptor stimulation, on the activity of single neurons in the nucleus basalis of Meynert (NBM), whose axons project to the cortex, were examined in urethane-anesthetized adult rats. Most of the neurons were not significantly influenced by innocuous mechanical cutaneous stimulation or baroreceptor stimulation, while they were excited by noxious mechanical cutaneous stimulation and chemoreceptor stimulation. The NBM neurons were excited more intensely and frequently by nociceptive mechanical stimulation to a fore- or hindpaw than by that to the back or face. The function of these NBM neurons is discussed.