Vaginitis is defined as any condition with symptoms of abnormal vaginal discharge, odor, irritation, itching, or burning. The most common causes of vaginitis are bacterial vaginosis, vulvovaginal candidiasis, and trichomoniasis. Bacterial vaginosis is implicated in 40% to 50% of cases when a cause is identified, with vulvovaginal candidiasis accounting for 20% to 25% and trichomoniasis for 15% to 20% of cases. Noninfectious causes, including atrophic, irritant, allergic, and inflammatory vaginitis, are less common and account for 5% to 10% of vaginitis cases. Diagnosis is made using a combination of symptoms, physical examination findings, and office-based or laboratory testing. Bacterial vaginosis is traditionally diagnosed with Amsel criteria, although Gram stain is the diagnostic standard. Newer laboratory tests that detect Gardnerella vaginalis DNA or vaginal fluid sialidase activity have similar sensitivity and specificity to Gram stain. Bacterial vaginosis is treated with oral metronidazole, intravaginal metronidazole, or intravaginal clindamycin. The diagnosis of vulvovaginal candidiasis is made using a combination of clinical signs and symptoms with potassium hydroxide microscopy; DNA probe testing is also available. Culture can be helpful for the diagnosis of complicated vulvovaginal candidiasis by identifying nonalbicans strains of Candida. Treatment of vulvovaginal candidiasis involves oral fluconazole or topical azoles, although only topical azoles are recommended during pregnancy. The Centers for Disease Control and Prevention recommends nucleic acid amplification testing for the diagnosis of trichomoniasis in symptomatic or high-risk women. Trichomoniasis is treated with oral metronidazole or tinidazole, and patients' sex partners should be treated as well. Treatment of noninfectious vaginitis should be directed at the underlying cause. Atrophic vaginitis is treated with hormonal and nonhormonal therapies. Inflammatory vaginitis may improve with topical clindamycin as well as steroid application.