The relation of the cortex, cerebellum, and basal ganglia and their participation in movement disorders is presented. Studies have shown that lesions to the cortex will produce contralateral paralysis while damage to the basal ganglia or cerebellum will result in movement abnormalities. These data provide support for the view that subcortical but not cortical structures initiate the control movement activity. It would appear that the basal ganglia and cerebellum receive signals from the auditory, visual, and somatosensory cortex integrate this information, and relay signals back to the motor cortex, which in turn sends out efferent fibers to the motor neurons of the spinal cord. The electronic and neurophysiological basis of the somatosensory evoked responses (SER) test following peripheral nerve stimulation and sensory recording in human cortex is given. Control values of SER peak to peak latency waveforms from 66 normal volunteers show the practicality of this test. Preliminary results using SER in patients are discussed from clinical case reports. The subjects had mild to marked movement disorders secondary to Parkinson's disease, vascular occlusion, multiple sclerosis, and spino-cerebellar degeneration. The potential of the SER as a clinical and experimental tool in evaluating movement abnormalities and other neuropathological conditions is presented.