Breastfeeding carries significant risks of mother-to-child transmission, especially in mothers newly infected during pregnancy or postpartum. In fact, breastfeeding may account for over 50% of new pediatric HIV cases globally each year. Women who are HIV-uninfected or whose HIV status is unknown should exclusively breastfeed their newborns for 6 months to reduce the morbidity and mortality from diarrheal, respiratory and other infections associated with not breastfeeding. At the same time, the use of safer sexual practices, including consistent condom use, should be reinforced during lactation to prevent maternal primary HIV infection. In women with acute HIV infection who breastfeed, there is approximately 29% risk of transmission to the newborn. In women who are HIV-infected, breastfeeding should be avoided if safe and affordable alternatives are available. However, in many areas with limited-resources, there are no good alternatives to breastfeeding and avoiding breastfeeding altogether will be associated with increased rates of non-HIV related infant illness and death and increased stigma for the mother. There has been increased attention to specific risk factors for HIV transmission associated with breastfeeding and incorporation of this information to help reduce risk when breastfeeding is desired. All new mothers should be taught how to breast feed properly and to seek prompt treatment if they develop a possible breast infection, breast sores or cracked nipples or if their infant develops oral lesions, such as thrush. Because of recent studies showing an increased risk of transmission associated with mixed breast and non-breast feeding, and because risk of transmission increases with duration of breastfeeding, current recommendations call for exclusive breastfeeding for up to 6 months with rapid weaning and transition to replacement feeds.