ObjectiveTo examine the association of clinical complications and age at diagnosis with survival for a cohort of children and adults with AIDS.DesignA population-based analysis of 734 children and 5584 adults diagnosed with AIDS from 1985 to 1990 in New York State.ResultsThe initial AIDS-defining diagnoses for 68% of children were lymphoid interstitial pneumonitis or infections specified in the Centers for Disease Control and Prevention's (CDC) pediatric AIDS case definition but not the CDC's 1987 adult AIDS case definition. Of opportunistic infections in both case definitions,Pneumocystis cariniipneumonia (PCP) was the most common initial AIDS diagnosis, occurring in 53% of adults, 47% of children aged < 6 months at diagnosis (n = 122) and 14% aged ≥6 months at diagnosis (n = 612). Median survival after AIDS diagnosis was 62 months for all children compared with 11 months for adults. For children initially diagnosed with conditions only in the pediatric case definition, median survival ranged from 27 to 62 months compared with less than 12 months for children and adults with PCP. Compared with children aged 6–54 months, the estimated hazards of death for younger and older children were 2.06 [95% confidence interval (Cl), 1.48–2.86] and 1.54 (95% Cl, 1.10–2.16), respectively.ConclusionChildren survived significantly longer than adults after AIDS diagnosis, but their survival varied by age at diagnosis. Differences in the types of common initial AIDS-defining diagnoses appear to contribute to the observed differences in survival.