The etiology of vaginitis can be difficult to prove. To determine the relationship between clinical criteria (symptoms and signs) and three causes of vaginitis, we prospectively evaluated 22 criteria in 123 unselected symptomatic patients. Diagnoses of Candida albicans and Trichomonas vaginalis infection were based on culture. Bacterial vaginosis was defined by the presence of 3 of 4 clinical criteria. Only 49% of our patients received diagnoses, and itching was the only symptom more frequently noted among those with diagnoses. Symptoms did not differ among the three infections, and lack of vaginal odor in yeast infection was the only significantly different physical sign. Yeast and trichomonads were seen on microscopy in 63% and 75% of culture-positive specimens. Bacterial vaginosis had no significant clinical criteria beyond those that defined the diagnosis. We conclude that presenting symptoms and signs in vaginitis evaluation have limited value, and that half of the women with vaginitis may lack a microbiologic diagnosis.