2-Thiouracil was firstly prepared by Wheeler, Liddle in 1908, then it had been discovered in seeds of Brassica cruciferae in 1941. In 1963, Maloof, Soodak discovered its antithyroid activity which resulted from its interference with the iodination of thyroxine precursors. In 1967 Cardeilhac proved that its mechanism of action as anticancer agent is due to its inhibitory effect on nucleic acid metabolism.