An effective technique was developed, which allowed rapid isolation of highly pure myelin basic protein (MBP) including its distinct isoforms. The procedure employs homogenization of central nervous system (CNS) tissue in chloroform, which specifically extracts MBP. Subsequently, methanol was used to convert the protein susceptible to quantitative transfer into the acidic aqueous phase. MBP was purified from bovine, chicken, fish, human, guinea-pig, mouse, rabbit, rat, and swine brains. Analysis on SDS-PAGE and immunoblotting using polyclonal MBP-specific serum recognized proteins corresponding to the sizes of previously identified MBP isoforms of 21.5, 18.5, 17.2, and 14.2 kDa and three predicted isoforms of 20.2, 16.0, and 13 kDa. The MBP obtained was readily soluble in water and possessed the capacity to induce experimental autoimmune encephalomyelitis in susceptible mice. The protein was also suitable for use as a substrate for protein kinases.