Multiple sclerosis (MS) is a demyelinating disease of the central nervous system (CNS). MS is classified into clinical subtypes, such as relapsing-remitting MS, primary and secondary progressive MS, benign MS and malignant MS. In Japan, the classification based on the lesion distribution is also commonly used. There are two subtypes in this classification, conventional MS, in which demyelinating plaques are disseminated within CNS, and optic spinal MS, or relapsing neuromyelitis optica, characterized by the selective involvement of the optic nerves and spinal cord. Clinical manifestations and MRI findings of the clinical subtypes and their immuno-pathology are reviewed with emphasis on the unique features of Japanese MS.