Multiple sclerosis is an insidious, intermittent or chronic progressive inflammatory, autoimmune disease of the central nervous system; it is a major cause of disability, especially in young adults. It affects women twice as often as men. The prevalence varies from 50 to 100 per 100,000 in moderate climate zones. Interferon beta-1b reduces frequency and severity of clinical attacks of relapsing-remitting multiple sclerosis and prolonged time until the progression of disability and time patients suffering from secondary progressive multiple sclerosis become wheelchair-bound.