Demyelinating disease, for example, multiple sclerosis, and its relation to hypersensitivity to central, nervous system antigens have been studied for more than 30 years. However, despite many efforts and a elaboration of methods, no correlation between antibodyproduction and clinical manifestation of disease has been demonstrated. On the other hand, the chemical and immunological properties of the encephalitogenic basic protein, Al (mol. wt. 18000) from central nervous system have been extensively studied. The amino acid sequences of human and bo vine central nervous system basic protein (Al) have been determined. This strongly basic mole cule has been shown to have a open conformation or random coil. The antigenic determinants responsible for its ability to induce EAE have been localized in discrete peptide fragments. Sensitization with peripheral nervous system tissue or myelin produces EAN. Recently, the chemical and immunologic properties of the two basic protein from peripheral nervous myelin (PI and P2 have been investigated). P1 protein from rabbit seems to have the same amino acid sequence as Al protein from rabbit. On the other hand, P2 protein is present only in peripheral nervous system and its stereic confor mation and amino acid sequences were quite different from Al protein or P1 protein. I am going to try a short review on these specific protein chemistries and discuss on the some relationships between these proteins and demyelinating diseases in this present paper.