Trichomoniasis is a common sexually transmitted disease associated with preterm birth, low birth weight, and increased susceptibility to infection with other pathogenic sexually transmitted microorganisms. Nucleic acid amplification tests for Trichomonas vaginalis have improved sensitivity for detecting infected individuals compared to existing culture-based methods. This prospective, multicenter U.S. clinical trial evaluated the performance of the automated Aptima T. vaginalis assay for detecting T. vaginalis in 1,025 asymptomatic and symptomatic women. Vaginal swab, endocervical swab, ThinPrep PreservCyt, and urine specimens were collected. Subject infection status was determined by wet-mount microscopy and culture. Aptima T. vaginalis assay performance was determined for each specimen type by comparison to subject infection status. Of 933 subjects analyzed, 59.9% were symptomatic. Aptima T. vaginalis clinical sensitivity and specificity were, respectively, 100% and 99.0% for vaginal swabs, 100% and 99.4% for endocervical swabs, 100% and 99.6% in ThinPrep samples, and 95.2% and 98.9% in urine specimens. Aptima T. vaginalis performance levels were similar in asymptomatic and symptomatic subjects. This study validates the clinical performance of the Aptima T. vaginalis assay for screening asymptomatic and symptomatic women for T. vaginalis infection.Trichomoniasis, a common sexually transmitted disease (STD) caused by the protozoan Trichomonas vaginalis, affects approximately 180 million persons per year worldwide, making it the most common nonviral STD agent in the world. An estimated 7.4 million new cases occur annually in the United States (1), and the disease has an overall prevalence of 3.1% (24). Both women and men can be infected, although symptoms are more common in women. Symptomatic women have a diffuse, malodorous, yellow-green vaginal discharge with vulvar irritation which may be confused with bacterial vaginosis. Infected men may temporarily have urethral irritation, mild discharge, or slight burning after urination or ejaculation (5). Many infections do not produce symptoms and when left untreated may lead to preterm birth, low birth weight, and pelvic inflammatory disease (5). T. vaginalis infection also increases susceptibility to infection with HIV (14,22,23). Effective and inexpensive antibiotic therapy for T. vaginalis infection is readily available, and detection and treatment of T. vaginalis in symptomatic or asymptomatic women with a high risk of STD are important to prevent disease acquisition, transmission, and associated complications.Currently, the gold standard for the diagnosis of T. vaginalis infection is culture; however, the sensitivity of commercially available culture has been reported to be 75% to 89% compared to amplified methods (13,20). Tests with improved sensitivity are needed to diagnose this prevalent STD. The Aptima Trichomonas vaginalis assay, an FDA-cleared, fully automated nucleic acid amplification test, has demonstrated high sensitivity and specificity compared to c...