Varicella-zoster virus (VZV) infections can cause severe disease in immunocompromised individuals. To evaluate the spectrum of VZV infections in human immunodeficiency virus (HIV)-infected children, we retrospectively analyzed all the cases of VZV infection in a cohort of children cared for at a hospital for infectious diseases in Bucharest, Romania. The records of 391 HIV-infected children admitted to the acquired immunodeficiency syndrome pavilion of Colentina Hospital during the period January 1, 1991, through March 31, 1992, were reviewed for evidence of VZV infection. The diagnosis of varicella or zoster was made clinically and information was collected concerning course of the illness, number of skin lesions, and clinical evidence of complications. Lymphocyte subpopulation typing, as an estimate of immune function, was performed by either a standard fluorescent activated flow cytometric method or by immunofluorescent technique. Thirty-eight cases of varicella (9.7%) and seven cases of zoster (1.8%) were adequately documented among the 391 records reviewed. The duration of varicella was prolonged; in 57% of the children it was greater than 10 days. Forty percent of children with varicella developed a complication, including superinfection of the skin, pneumonia, or thrombocytopenia. None of the children developed clinical hepatitis or encephalitis. Two children (5%) died during varicella, both of respiratory failure. None of the 7 children with zoster had chronic, recurrent, or disseminated lesions. Lymphocyte subset analysis was available for 22 of 38 children with varicella and 3 of 7 children with zoster. Fifteen of the 22 children had normal, age-adjusted, absolute CD4 counts within 3 months of the diagnosis of varicella. All 3 children with zoster who had lymphocyte subset analysis had low CD4 counts and absolute numbers. None of the 45 children received antiretroviral therapy and only 1 child with varicella and 1 with zoster received acyclovir. The spectrum of VZV infection in this hospitalized group of HIV-infected children was broad. The majority (57%) experienced a prolonged course of disease and a higher rate of complications than normal children hospitalized with varicella.