Anthraquinone is used as an intermediate in the manufacture of dyes and pigments, an additive in the kraft pulping process in the paper industry, a catalyst in the isomerization of vegetable oils, an accelerator in nickel electroplating, and as a bird repellant. The National Toxicology Program is conducting a class study of naturally occurring quinones containing the anthraquinone ring; anthraquinone is the parent compound of this class. Male and female F344/N rats and B6C3F 1 mice were exposed to anthraquinone (approximately 99.8% pure by gas chromatography and liquid chromatography) in feed for 14 weeks or 2 years. Genetic toxicology studies were conducted in Salmonella typhimurium, mouse bone marrow cells, and mouse peripheral blood erythrocytes.