HIV infection has been a major cause of morbidity and mortality since the first cases of AIDS among children were reported in 1982 in the United States. Considerable advances, especially in the past 5 years, in the understanding of the pathogenesis, diagnosis, treatment, monitoring, and prevention of HIV infection in children have changed the rate of pediatric HIV infection in the United States. Efforts to maximally decrease perinatal HIV transmission in the United States are ongoing. Physicians must try to prevent HIV infection among women, especially adolescents.