Inorganic, analytical, and radiochemistry of thorium is reviewed. A table of thorium isotopes is given. The features of thorium chemistry of interest to radiochemists include metallic thorium, soluble and insoluble salts and coprecipitation characteristics, complex ions, chelate complexes, extraction of the TTA complex of thorium into organic solvents, and ion exchange behavior. A collection of detailed radiochemical procedures for thorium is given. (J.E.D.)