Children born to mothers infected with the human immunodeficiency virus (HIV) present specific problems to the pediatric health care worker. Although only one third of children born to these mothers are actually infected with HIV, the identification of these children is complicated by the presence of passively acquired maternal antibodies and the immunosuppressive effects of HIV infection. This article reviews the latest developments in the diagnosis of HIV infection in children. The efficiency of perinatal transmission of the virus from mother to child is approximately 25% to 40%. The natural history of pediatric HIV infection indicates that although most children present with symptoms in the first years of life, some, as in the case of the adult population, are asymptomatic for years and develop manifestations of HIV infection after 6 to 10 years. Children with HIV infection differ from adults in several ways,ie, they present withPneumocystis cariniipneumonia in the 1st year of life with what appear to be normal CD4 lymphocyte counts and they have increased susceptibility to recurrent bacterial and viral infections, an increased incidence of lymphocytic interstitial pneumonitis, a wide spectrum of neurologic and developmental abnormalities, and a decreased incidence of Kaposi's sarcoma. The introduction of zidovudine, an effective antiretroviral agent, and its analogues into pediatric practice has given new hope to the treatment of HIV infection. The risk of nosocomial acquisition of HIV is discussed, as are current strategies for disrupting transmission in health care workers who have been directly exposed to contaminated body fluids via either a needle stick, open wound, or open mucous membrane.