This study tested the hypothesis that the transmission of cutaneous sensory information to single somatosensory (SI) cortical neurons may be modulated or gated during movement or "arousal" behaviors. The results showed that movement by itself was associated with a powerful suppression ofthe sensory input to SI cortical cells from their cutaneous receptive fields. Control experiments showed that this sensory suppression during movement could not be due to either(i) an obscuring of the sensory responses by the large increases in the spontaneous discharge rates of these cells generally found during movement, (ii) an occlusion of the sensory response to the test stimuli by the increased activity in parallel sensory channels caused by repetitive foot contact during locomotion, (iii) distraction of the animal's attention or, (iv) differences in the motivational or arousal states associated with various movement states, because sensory suppression was found in both grooming and treadmill locomotion. It was also found that, in the absence of movement, strong arousal was associated with a slight increase in sensory responsiveness and a decrease in spontaneous discharge rate. The finding that movement rather than arousal or attentiveness caused the most potent modulation of the sensory responsiveness and firing rates of SI cortical cells suggests that this cortical area may be closely integrated with central nervous system motor functions.