A comparison is made between oral ornidazole in a single 1-5 g dose and tinidazole given in a 2 g dose using a double-blind technique. All the 45 women with Trichomonas vaginalis infection who were treated with ornidazole were cured. In the tinidazole-treated group 41 out of 43 women had negative cultures after treatment. Tolerance was good in both groups.