Anaerobic infections of the upper genital tract are common. Antibiotic regimens designed to inhibit anaerobes markedly reduce morbidity. A vaginal infection associated with an increased concentration of anaerobic bacteria (bacterial vaginosis) has been recently linked to a wide variety of upper genital tract infections. Bacterial vaginosis has an important role in the development of clinical chorioamnionitis, postpartum endometritis, posthysterectomy vaginal-cuff cellulitis, postabortion pelvic inflammatory disease, and upper genital tract infections such as amniotic fluid infection and chorioamnion infection associated with premature delivery.