Stirimazole is an imidazole derivative patented by Lilly Industries Ltd. as an antiparasitic agent effective against Trypanosoma congolense, T. gambiense, T. rhodesiense, and T. cruzi. Stirimazole inhibited Trichomonas vaginalis in vitro at 0.225 μg/ml and eliminated infected lesions in mice at 20 mg/kg orally. Stirimazole eliminated intestinal amebiasis in rats at 50 mg/kg orally and hepatic amebiasis in hamsters at 100 mg/kg i.p. Stirimazole was curative against Trypanosoma rhodesiense, Trypanosoma cruzi, Trypanosoma gambiense, and Trypanosoma congolense in mice at 25, 100, 12.5, and 25 mg/kg (4 times, i.p.), respectively, and against Trypanosoma vivax in calves at 25 mg/kg i.v.