The pace of research on the pathogenesis and treatment of multiple sclerosis, the principal human demyelinating disease of the central nervous system, has intensified in the past 3 years, due in part, to the application of advances in molecular and cellular immunology. Many lessons that have been learned in an animal model of central nervous system demyelinating disease, experimental allergic encephalomyelitis, also apply to multiple sclerosis and certain successful approaches for the treatment of this disease are now being attempted in humans.