In the developed world, antiretroviral therapy (ART) administered to the mother during pregnancy and intrapartum and to the infant in the neonatal period has resulted in a reduction of the overall risk of vertical transmission of HIV-1 to approximately 8%. In some settings, ART combined with cesarean section and a reduction in duration of ruptured membranes has resulted in a further lessening of risk to levels < or = 2 percent. A number of less expensive and greatly abbreviated ART regimens, useful for application in resource poor settings, also have resulted in reductions of mother-to-infant transmission of HIV-1 by 33 to 50% compared to baseline. A multitude of studies have shown these drugs to be safe for mothers, fetuses, and newborns. Breastfeeding seems to represent a risk factor that adds to the risk of vertical transmission, especially in infants who are fed a combination of breastmilk and other liquids and solids. Studies designed to assess the possible benefits of treating genital ulcer disease, chorioamnionitis, mastitis, and malnutrition in HIV-infected women, and of applying antiseptic washes to the cervix and vagina during labor, are in progress.