OBJECTIVE To describe epidemiologic characteristics of Pneumocystis carinii pneumonia (PCP) among children with perinatally acquired human immunodeficiency virus (HIV) infection to guide prevention efforts. METHODS National acquired immunodeficiency syndrome (AIDS) surveillance of children aged 0 through 12 years, a multisite surveillance study of HIV infection in children aged 0 through 12 years, and the national HIV serosurvey of childbearing women. METHODS Surveillance conducted by state and local health departments and reported to the Centers for Disease Control and Prevention 1982 through 1992. RESULTS Pneumocystis carinii pneumonia was reported in 1374 (37%) of 3665 perinatally acquired AIDS cases. Over half of these cases occurred between 3 and 6 months of age. In 183 (64%) of 275 PCP cases reported in the special surveillance study, PCP was the first or only AIDS-defining condition diagnosed, and in 44% of cases, the child had not been evaluated for HIV infection before diagnosis of PCP. The estimated median survival after diagnosis of PCP was 19 months. CONCLUSIONS Pneumocystis carinii pneumonia is a common and serious opportunistic infection that affects young children with HIV infection. Effective efforts to prevent PCP in this population will require identification as early as possible of children who may be infected with HIV.