Clinical isolates of Trichomonas vaginalis were obtained from women consecutively enrolled in a study of partner notification. Testing of susceptibility to metronidazole and tinidazole was performed. Resistance to metronidazole and tinidazole was present in 17/178 (9.6%) and 1/178 (0.56%) strains, respectively. In vitro resistance was poorly correlated with clinical response to treatment. Copyright © 2006, American Society for Microbiology. All Rights Reserved.