The nuclei of the neocerebellum receive inputs from somatosensory receptors and the motor cortex. In cats, the discharge of those nuclear neurons which were driven by passive movement of a limb segment in one direction was suppressed by stimulation of the cortical site from which movement was evoked in the opposite direction (Larsen and Yumiya 1979a). The cortical-evoked suppression of cerebellar neurons resulted in a disfacilitation of red nucleus neurons whose discharge elicited movement in the same direction as the cortical neurons from which the suppression was evoked and which were driven by passive movement in the opposite direction (Larsen and Yumiya 1980a). The purpose of this study was to determine if the cortical modulation of rubral neurons is organized in macaque monkeys in the same way as it is in cats. Red nucleus neurons were characterized by their response to natural stimulation of somatosensory receptors, and their response to cortical microstimulation was examined in peristimulus time histograms (PSTHs). Cortical stimulation evoked a short-latency corticorubral facilitation and a longer latency response which was presumed to be mediated by the cerebellum and which was composed primarily of suppression but was sometimes preceded by a brief facilitation. As was true in cats, over half of the rubral neurons which were driven by passive movement of a limb segment in one direction responded with a facilitation-suppression to stimulation of the “agonistic” cortical site from which movement was evoked in the opposite direction, but only a few responded to stimulation of the “antagonistic” cortical sites. Similar responses were evoked in many rubral neurons by stimulation of other cortical sites from which movement was elicited about the same joint in a different plane or at a joint adjacent to that whose passive movement drove the rubral neuron. Responses were found in neurons which received somatosensory input from proximal or distal limb segments and in neurons in the parvocellular or magnocellular divisions of the nucleus, although the corticorubral facilitation was found more frequently in parvocellular neurons. In conclusion, the motor cortical modulation of the red nucleus and cerebellum is similar in monkeys and cats, and is the same for the proximal and distal limb representation.