Evoked potentials to peroneal nerve stimulation are being recorded from surface electrodes placed over the spine of normal human subjects and patients with spinal cord pathology. Wave form configuration at all spinal leads is being defined as are conduction characteristics of the response. The effect of maturation on these potentials is being studied. Similar studies are being performed in cats to determine the generator sources of these potentials. Somatosensory evoked far field potentials to median nerve stimulation which arise in subcortical structures are being recorded from the scalp of normal human subjects and patients with brainstem and cerebral pathology. Correlation is being made between the site of the lesion as judged by the clinical evaluation and abnormalities of the evoked potentials.