1. In anesthetized cats, potential changes were recorded intracellularly from the red nucleus neurons during single shock stimulation of the sensorimotor cortex, internal capsule and cerebral peduncle. 2. These stimulations monosynaptically produced EPSPs with characteristically slow rising time course. The EPSP from internal capsule interfered with that from cortex indicating that these EPSPs were produced through the same fibers. The excitatory fibers were identified as the cortico-rubral projection by their conduction velocity, somatotopical arrangement and degeneration after ablation of the sensorimotor cortex. 3. Hyperpolarization of the membrane by intracellular injection of currents did not influence appreciably the EPSP from the internal capsule while it greatly increased the EPSP from the nucleus interpositus. It thus appears that corticorubral fibers make synaptic contact with the remote dendrites of RN-cells, while axons of interpositus neurons impinge on or near the soma. 4. Cortico-rubral EPSPs induced spikes at the initial segments of red nucleus cells after electronic propagation from remote dendrites. 5. Small postsynaptic potentials of slow time course were seen to occur spontaneously, presumably by bombardments along the cortico-rubral fibers.