Electrical stimulation was applied to the spinal cord of 75 patients who had demyelinating and degenerative diseases of the central nervous system, and 3 patients who had sustained spinal cord injuries. The electrical energy was delivered to the central nervous system by the percutaneous technique. The amount of electrical energy required to produce the perception of paresthesias was measured in 11 patients. The minimum power necessary was 76.89 muW, the maximum was 868 muW, and the average was 448.8 muW. The patients were evaluated by 4 examiners by means of routine neurologic examination, videotape movies, and measurement of urinary bladder function. Continued improvement in neurological status, which allowed the patient to live a better lifestyle, occurred in 30 of the 61 patients with multiple sclerosis, and 6 of the 10 patients with ataxia. The patient with transverse Myelitis, the patient with primary lateral sclerosis, and 1 patient with olivopontocerebellar atrophy; also noted similar enhancement of neurological function. The patients with amyotrophic lateral sclerosis and spinal cord injuries had no changes of significance. Thirty-two out of 44 patients who were ambulatory had significant improvement, whereas 10 of the 19 patients who were not ambulatory had improvement. There was no evidence that electrical stimulation of the spinal cord, when applied via dorsally placed percutaneous electrodes and when carried only to the perception of a paresthesias, has any adverse effect on neurological function. It is hypothecated that the electrical current alters neurotransmitters to enhance the transmission along nervous and neurochemical pathways. The exact mechanisms are unknown at the present time.