In many developing countries, because the prevalence of maternal HIV infection is high (more than 30% in some sub-Saharan African countries) and the resources commonly used to prevent transmission in developed countries are generally not available, transmission of HIV from mother to infant is a devastating problem. Countries already experiencing infant mortality rates 10- to 20-fold greater than those in developed countries can expect a doubling of infant and childhood mortality due to HIV. Those infants who escape infection themselves can expect to be orphaned in early childhood. Low-cost antiviral therapy can reduce transmission substantially, but many countries do not have the infrastructure to screen pregnant women for HIV and appropriately treat the mothers and infants. In developing countries, reduction in maternal-child transmission is feasible, but will require substantial additional resources and a well-functioning obstetric care system.