Vaginitis is the most common gynecologic diagnosis in the primary care setting. In approximately 90 percent of affected women, this condition occurs secondary to bacterial vaginosis, vulvovaginal candidiasis or trichomoniasis. Vaginitis develops when the vaginal flora has been altered by introduction of a pathogen or by changes in the vaginal environment that allow pathogens to proliferate. The evaluation of vaginitis requires a directed history and physical examination, with focus on the site of involvement and the characteristics of the vaginal discharge. The laboratory evaluation includes microscopic examination of a saline wet-mount preparation and a potassium hydroxide preparation, a litmus test for the pH of vaginal secretions and a "whiff" test. Metronidazole is the primary treatment for bacterial vaginosis and trichomoniasis. Topical antifungal agents are the first-line treatments for candidal vaginitis.