▪ Abstract Multiple sclerosis (MS) is a common inflammatory disease of the central nervous system (CNS). Diagnosis rests upon identifying typical clinical symptoms and interpreting supportive laboratory and radiological investigations. The etiology is unknown; however, strong evidence suggests that MS is an autoimmune disease directed against CNS myelin or oligodendrocytes. Genetic factors are important in the development of MS. Contributing environmental determinants (possibly including infectious agents) appear important but remain unidentified. Both cell-mediated and humorally mediated immune mechanisms contribute to pathological injury. Axonal damage occurs in addition to demyelination and may be the cause of later permanent disability. Distinct pathological subtypes may differentiate among patients with MS. Treatment is directed at acute attacks (with corticosteroids) and reduction of attack frequency (primarily with type-1 β interferons and glatiramer acetate). Research into the causes and treatments of MS has expanded our knowledge of this disease and promises improved care for MS patients in the future.