Stimulation of the caudate nucleus results in more marked inhibition of movements elicited by stimulation of the cortex of the same than the opposite side. In the case of spontaneous movements caudate stimulation exerts a general, bilateral, inhibitory effect which is essentially the same on both sides of the body. Spontaneous activity is more easily inhibited than is cortically induced movement and is obtained from a greater area of the striatum. Those areas from which inhibition of cortically induced movement is most easily evoked coincide rather closely with the regions through which corticistriate fibers run in closely grouped bundles. The most notable of these bundles is the subcallosal fasciculus. No evidence favoring the existence of a definite somato-topical projection of the striatum was observed. The inhibitory effect obtained upon striatal stimulation is not related to irritation of the ventricular ependyma, stimulation of the callosum nor to excitation of thalamocortical nor corticifugal fibers travelling in the internal capsule. Inhibition of the above type cannot be evoked by stimu- lation in the vicinity of the head of the caudate if this is removed. The inhibition of movement by cortical stimulation as previously discovered by other observers is abolished by narcotisation or injury of large portions of the striatum but is not affected by pyramid section. This indicates that the cortical inhibitory effect travels through the striatum.