A series of 2-(5-nitro-2-furyl) and 2-(5-nitro-2-thienyl)-5-substituted-1, 3, 4-thiadiazoles (5a–d and 6a–j) were synthesized and evaluated against Leishmania major promastigotes using 3H-thymidine incorporation. Most of the compounds showed activity better than the reference drug sodium stibogluconate (Pentostam). The most active compound was 6c (IC50= 0.1 μM).