Abstract 1. 1. The behavior of crystalline insulin of bovine origin in partition column chromatography between the systems composed of 2-butanol equilibrated with 0.1 N solutions of perchloric, nitric, hydrobromic, hydrochloric, methylsulfonic, or hydroxyethylsulfonic acids is reported. 2. 2. Elution curves which indicated heterogeneity in the eluted fractions of insulin were noted in several of the solvent systems. 3. 3. The degree of resolution of components increased with decreasing distribution constant of the insulin in the 2-butanol-0.1 N acid systems. 4. 4. A relationship was noted between the distribution constant of the acid in 2-butanol-water and the distribution constant of the insulin in 2-butanol-0.1 N aqueous acid systems.