BACKGROUND: Few prospective studies have measured survival rates among human immunodeficiency virus (HIV)-infected children in sub-Saharan Africa prior to the availability of antiretroviral therapy. METHODS: In the context of an observational study of the immunogenicity of measles vaccine in Zambia, we prospectively followed up children from approximately 9 months of age and assessed survival rates, risk factors for mortality, and circumstances at the time of death according to HIV-infection or HIV-exposure status. RESULTS: There were 56 deaths among 492 study children during follow-up to 3 years of age. Thirty-nine percent of the 105 children with HIV infection died during the study period, compared with 5.0% of the 260 HIV-seropositive but uninfected children and 1.6% of the 127 HIV-seronegative children. Estimated survival probabilities from 9 through 36 months of age were 52% among HIV-infected children, 95% among initially HIV-seropositive but uninfected children, and 98% among HIV-seronegative children. In multivariable analyses, history of a clinic visit within the 4 weeks prior to study entry (adjusted hazard ratio, 4.6; 95% confidence interval, 1.5-13.5), hemoglobin level <8 g/dL at study entry (adjusted hazard ratio, 4.4; 95% confidence interval, 1.5-12.6), and CD4(+) T lymphocyte percentage <15% at study entry (adjusted hazard ratio, 3.2; 95% confidence interval, 1.1-9.5) were associated with mortality among HIV-infected children. CONCLUSIONS: Only approximately one-half of HIV-infected Zambian children who were alive at 9 months of age survived to 3 years of age, supporting the urgent need for the prevention of mother-to-child transmission of HIV and the early diagnosis and treatment of HIV infection in children in sub-Saharan Africa.