Abstract A new series of potent uridine phosphorylase inhibitors have been prepared from barbituric acid. Among them, 1-[(2-hydroxyethoxy) methyl]-5-)(m--benzyloxy) benzylbarbituric acid (37, BBBA) is the most promising having a K i value of 1.1±0.2 nM with uridine phosphorylase from human liver. The new inhibitors are easily synthesized and are better inhibitors of human uridine phosphorylase than their uracil counterparts.