Myelin basic protein (BP) has the capacity to induce experimental allergic encephalomyelitis (EAE) in animals as well as to prevent and suppress EAE. Immunoreactive BP or BP fragments appear in cerebrospinal fluid (CSF) in persons with multiple sclerosis in acute disease periods and in individuals with acute damage to central nervous system myelin. Humoral and cellular immune responses, especially in the CSF, may occur but are of uncertain effect in the etiology and pathogenesis of MS. Attempts to use BP to suppress MS have disclosed no therapeutic benefit.