The case histories of 27 children with Pneumocystis carinii pneumonia (PCP) who were followed up in the AIDS Program at the Children's Hospital of New Jersey, Newark, are reviewed. The mean and median age at PCP diagnosis were 10.8 and 7.7 months, respectively. All of the children had other clinical evidence of infection with the human immunodeficiency virus that was documented prior to the diagnosis of PCP or found at the time of PCP diagnosis. Most patients who presented to the hospital were acutely ill, and complications of treatment occurred in 70%. Overall, 89% of the patients died and 70% survived for less than 6 months after diagnosis of PCP. Median survival after the diagnosis of PCP was only 2.0 months and the median life span of children with PCP was only 14.4 months. Only 40% of children with PCP had CD4 lymphocyte counts at or below the threshold for institution of PCP prophylaxis in adults of 200 x 10(6) cells/L (200 cells/mm3).