There are three major causes of vaginitis symptoms that primary care practitioners should be able to diagnose and treat expertly. Recent investigations have shown that bacterial vaginosis, the most common cause of vaginitis symptoms in patients not seen in sexually transmitted disease clinics, has a multifactorial etiology: Gardnerella vaginalis is universally present but is not, per se, the etiologic agent. Diagnosis and treatment are based, therefore, on evidence of a disturbed bacterial ecology as well as the presence of "clue" cells that indicate the presence of Gardnerella. Trichomonas vaginitis is usually easy to diagnose, but treatment failures occasionally occur. Some strains of Trichomonas vaginalis may be relatively resistant to metronidazole, and short-course therapy may lead to reinfection from sexual partners. Candida vulvovaginitis, the third major type of vaginitis, is not a sexually transmitted disease and should be viewed as vaginal "thrush." Earlier treatment regimens have been simplified by the introduction of more potent antifungals.