Antileishmanial activities of thirty-five synthetic chalcones have been examined. Among them, ten compounds (4, 6, 16, 22, 23, 24, 25, 29, 35 and 37) exhibited potent in vitro activity (IC50 range from 1.70 to 8 μM) against extracellular promastigotes and intracellular amastigotes form of Leishmania donovani. Two promising compounds 22 and 37 were tested in vivo in L. donovani/hamster model. Chalcone