Patients w/ a single clinical event suggestive of multiple sclerosis (clinically isolated syndrome), to delay progression to definite multiple sclerosis. In relapsing-remitting multiple sclerosis, for the reduction of frequency & degree of severity of clinical relapses in ambulatory patients, characterized by at least 2 attacks of neurological dysfunction over the preceding 2-yr period, followed by complete or incomplete recovery. In secondary progressive multiple sclerosis, for the reduction of frequency & severity of clinical relapses & for slowing the progression of disease.