Multiple sclerosis (MS) is a relapsing and often progressive disorder of the central nervous system characterized by demyelination. Some reports show that TPE is effective for acute MS; however, TPE is often performed for non-acute phase MS patients who are unresponsive to steroids with lack of evidence of effectiveness. On the other hand, NMO is considered as an autoimmune disease associated with NMO-IgG. The effect of TPE on NMO patients is not consistent and the demyelination of optic nerve can be a part of MS. This session will discuss controversial application of TPE on both diseases.