This retrospective cohort study examined a nationally representative sample of 945 Brazilian children (ages 0-12 years) diagnosed with AIDS in 1999 to 2002 and followed through 2007. The probability of survival to 60 months was 86.3% (95% CI, 84.1%-88.5%). This compares with 52.8% (95% CI, 41.9%-60.8%) in a study of cases diagnosed in 1983 to 1998. These results demonstrate substantial improvement in survival for children with AIDS in Brazil.