Bacterial vaginosis is the most common cause of vaginal discharge. Recent studies have confirmed its association with pelvic inflammatory disease and adverse pregnancy outcomes. Bacterial vaginosis is treated with oral metronidazole (given either as a single dose or a seven-day course) or clindamycin. Treatment with topical clindamycin or metronidazole is also effective in returning the vaginal flora to normal but may be less effective in preventing the increased incidence of adverse pregnancy outcomes.