Rats were anesthetized with Nembutal and suspended in a stereotaxic apparatus so that their limbs contacted the outer surface of a 30-cm diameter wheel. Stimulation in the lateral hypothalamus (0.5 msec cathodal pulses at 50 Hz, up to 150 microA) produced locomotor stepping which turned the wheel. During continuous locomotion maintained by electrical stimulation, tactile stimulation was applied manually for 5-sec periods to various body regions in six subjects. Profound inhibition of locomotor stepping was produced in all subjects by mild pressure applied to the nose or the vibrissae pad. Vibrissae pad stimulation either ipsilateral or contralateral to the stimulation site was effective. Stroking of the vibrissae inhibited locomotion in only 2 of 6 subjects and in these cases the effective stimulation was contralateral to the brain stimulation site. With pressure applied to more caudal body regions, including the dorsum, the abdomen and the tail, the inhibition was less pronounced and less consistent than that produced by pressure on the snout region. The findings indicate that the tactile system provides an important modulation of locomotion and that the anesthetized locomoting rat offers a useful preparation for its further study.