Infestation with T. vaginalis is a common and potentially morbid infection. In addition to reproductive tract discharge and irritation, infection with this protozoa is increasingly recognized to be associated with reproductive tract complications, including postabortal infection, postcesarean infection, preterm birth, and PROM. Clinical diagnosis is often difficult and newer approaches using specific antigen and nucleic acid technologies will probably replace "wet prep" microscopic techniques. Effective treatments continue to depend on oral metronidazole treatment. Cure of resistant strains, which remain rare, depends on administration of higher, more prolonged doses of metronidazole. Improved understanding of the natural history, pathobiology, diagnosis, and treatment of this common protozoa is urgently needed. Practitioners should consider routinely screening and treating women for trichomoniasis before any reproductive tract surgery (chorionic villi sampling, hysterectomy, cesarean section, dilatation and curettage, therapeutic abortion, and so on), after changing sexual partners, and during pregnancy. Both symptomatic and asymptomatic patients and their sexual contacts should be treated.