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Methods have been developed for the purification of concentrates of corticotropin-B by ion-exchange techniques. Corticotropin-B undergoes exchange on columns of the cation-exchange resin Amberlite IRC-50 buffered with sodium ions, while inert materials are eluted by washing with aqueous pyridine and aqueous acetic acid solutions. The active principle is the11 removed from the resin by dilute hydrochloric acid, and is recovered as a solid hydrochloride, which is free of inorganic salts, and which possesses an activity of 250 to 300 u./mg. Considerable purification is also obtained by fractionation on columns of oxycellulose. In these processes, the presence of a reducing agent such as sulfite or hydrogen sulfide has inhibited inactivation and has made possible better separations and more highly active products.