The immunologic and clinical abnormalities associated with pediatric human immunodeficiency virus (HIV) infection are reviewed, the rationale for using intravenous immune globulin (IVIG) to prevent serious bacterial infections is described, and clinical experience with IVIG for this indication is summarized. Immunologic and clinical abnormalities seen in pediatric HIV-infected patients differ from those seen in adult HIV-infected patients. In pediatric patients, impaired B-cell activity is an early and prominent manifestation of HIV infection. Infants infected with HIV do not develop the antigen-specific B- and T-cell clones required for immunologic memory, amplification, and production of specific antibodies. B-cell defects and lack of memory B cells result in a high rate of serious bacterial infections in HIV-infected children compared with adults. Natural killer cell dysfunction may also increase HIV-infected children's susceptibility to secondary infections. IVIG therapy in HIV-infected pediatric patients is based on evidence of impaired antibody function in these patients, although this use remains controversial. Case reports and one unblinded comparative study published during the 1980s suggest that IVIG may decrease morbidity and improve cellular and humoral immune response. One recent large-scale, double-blind, placebo-controlled study showed that IVIG 400 mg/kg every 28 days can decrease the morbidity associated with serious bacterial infections in HIV-infected children with CD4 cell counts of > 200 cells/cu mm. Another study involving HIV-infected children receiving concurrent zidovudine demonstrated that IVIG helped prevent serious bacterial infections in children who were not concurrently receiving trimethoprim-sulfamethoxazole but not in those who were. Although IVIG has not been shown to alter mortality in HIV-infected children, regular use may decrease the morbidity associated with serious bacterial infections.