Studies indicate that there are proteins with different chemical properties in unheated tuberculin. The relative amounts of these proteins vary in different tuberculins from the same strain of bacillus grown at different times. Methods of analysis included N determination, UV spectral absorptions, electrophoresis, paper chromatography, and skin tests. Unheated tuberculin filtrates were fractionated and the proteins isolated and studied. Several different proteins were identified and grouped in classes according to their solubilities and speed in electrophoresis: (A) a soluble but slow protein; (B) a soluble and fast protein; (C) an insoluble and fast protein; and glycoprotein containing a soluble, slow, and carbohydrate-rich fraction. Diaminopimelic acid is abundant in the glycoprotein fractions and present to a slightly less extent in the A proteins.