To better understand the natural history of severe pediatric human immunodeficiency virus infection, reported cases of perinatally acquired pediatric acquired immunodeficiency syndrome (AIDS) in New York City were examined for differences in survival and age at diagnosis before and after implementation of an expanded case definition in 1987. One hundred ninety-six children reported through August, 1987, and 333 children reported between September, 1987, and February, 1990, and diagnosed through 1989 were compared. Significant differences were not found in survival by either gender or race/ethnicity although Hispanics were slightly more likely to be diagnosed with Pneumocystis carinii pneumonia (PCP) and blacks with lymphocytic interstitial pneumonitis (LIP). The most striking differences were noted regardless of race between children whose earliest AIDS-specific diagnosis was PCP and those whose earliest diagnosis was LIP. In the group reported through August, 1987, median survival from birth was 10 months with PCP vs. 54 months with LIP, median age at diagnosis 5 months vs. 20 months, and median survival after diagnosis 2 months vs. 22 months, respectively. Twelve-month survival for PCP improved in the two time periods examined, but survival with LIP did not. After implementation of the 1987 case definition, bacterial infections replaced LIP as the second most common diagnosis. This study provides data on children diagnosed and reported with AIDS. Ongoing prospective studies of children who have a full spectrum of human immunodeficiency virus infection with and without reportable AIDS wil further elucidate survival in children infected with human immunodeficiency virus.