Live varicella virus vaccine was administered to 10 stable human immunodeficiency virus type 1 (HIV-1)-infected children. Subjects were monitored for adverse reactions, HIV-1 plasma levels, CD4 T cell counts and immune responses. The vaccine was well-tolerated. Varicella-zoster virus-specific lymphocyte proliferative responses were detected in all subjects by 4 weeks and in 9 of 10 subjects 1 year after vaccination.