An orange-coloured nitrogenous pigment, "polystictin," has been isolated from the Australian polyporous fungus Coriolus sanguineus (Fr.), earlier called Polystictus cinnabarinus or P. sanguineus. This has been found to be identical with the "cinnabarin" recently isolated by Gripenberg from the Finnish fungus Trametes cinnabarina (Jacq.). Its analytical composition fits best the formula C29H22O10N4 but does not exclude the formula C14H10O5N2 suggested by Gripenberg. Half of its nitrogen is removed as ammonia by hydrolysis with aqueous alkali. Short treatment with methanolic potassium hydroxide, however, removes two molecules of CO2 (per C29; one per C14), without loss of nitrogen. Polystictin (cinnabarin) is accompanied by another pigment, polystictinin, which differs from the former by its greater solubility in organic solvents, and by possessing a sharp melting point. Other water- and ether-soluble yellow to orange substances are also present in small amounts. No evidence could be found for antibiotic action against Gram-negative organisms of any of these fungal pigments.