During the prospective follow-up of 64 babies at risk for perinatal HIV-1 infection because their mothers were seropositive, and of 130 control babies whose mothers were seronegative, we studied the occurrence of complications of bacillus Calmette-Guérin (BCG) immunization and its ability to induce cutaneous reactivity to tuberculin. Babies born both to HIV-1-positive and HIV-1-negative mothers received BCG immunization during their first month of life according to the Expanded Programme on Immunization (EPI) recommendations. Local and regional complications of BCG vaccine were looked for at 3, 6 and 9 months after inoculation. A tuberculin skin test was performed at 6 or 9 months of age. Most babies born to HIV-1-positive mothers were later classified as infected or uninfected according to their clinical condition and/or serological status at 18 months of age. The mean duration of the follow-up was 36 months (range 30-40 months). No chronic or deep ulcerations at the site of injection or disseminated forms of BCG infection were observed. The frequency of BCG-related lymphadenitis in the group of HIV-1-infected children (24%) did not differ significantly from the group of uninfected children (19%; Fisher test: P = 0.73). In contrast, the tuberculin skin test responses were positive less often in the group of HIV-1-infected children (33%) than in the uninfected group (83%; Fisher test: P = 0.007). Because BCG vaccine appears to be safe--even when given to perinatally infected babies--continuation of the BCG immunization policies of the EPI is justified, especially in view of the growing incidence of tuberculosis as a complication of HIV infection.