The panel included clinicians experienced in the diagnosis and management of children with HIV infection, public health physicians, and representatives of professional associations and Federal health agencies. The classification system was designed mainly for public health purposes, including epidemiologic studies, disease surveillance, prevention programs, and health care planning and policy. Children who fulfill the definition of HIV infection may be classified into one of two mutually exclusive classes, based on the absence or presence of clinical signs and symptoms. Class Pediatric-1 (P-1) is further subcategoried on the basis of the presence or absence of immunologic abnormalities, whereas Class P-2 is subdivided by specific disease patterns. A child classified in P-2 because of the presence of signs and symptoms should not be reassigned to Class P-1 if signs and symptoms resolve. New information and diagnostic tests may result in the revision of the classification system. Tables and 12 references.