Breastfeeding prevents millions of infant deaths each year throughout the world but causes at least one-third of all pediatric HIV infections. The first randomized trial of breastfeeding versus formula feeding, reported from Nairobi in March 2000, demonstrated an improved outcome for babies of highly selected HIV-positive mothers assigned to formula feed. However, several conditions must be in place and accepted before such replacement feeding can increase HIV-free survival. The proportion of sub-Saharan African women who have access to and will accept these conditions is small. In the short term, efforts to make breastfeeding safer will probably benefit a greater number of African babies.