Nine children with immunodeficiency syndromes who developed persistent or disseminated Bacillus Calmette-Guérin (BCG) infections after BCG vaccination at birth were observed in Santiago, Chile, over a period of 10 years. This represents a risk for persistent or disseminated BCG infections of 3.4/1,000,000 vaccinated newborns. This may closely reflect the incidence of severe combined immunodeficiency syndromes, cellular immunodeficiency syndromes and chronic granulomatous disease in the study area. The clinical presentation and course of the infection varied considerably depending on the underlying immunodeficiency syndrome. Two patients with severe combined immunodeficiency presented with cutaneous nodules in the absence of any local reaction at the site of BCG vaccination. Both patients died of disseminated BCG infection within the first year of life. Four patients with cellular immunodeficiency syndromes presented with regional lymphadenitis resistant to treatment after the fifth month of life. Three of these patients had specific unresponsiveness to tuberculin and survived from 5 to 6 years of age. Two boys with X-linked chronic granulomatous disease presented with regional lymphadenitis in the first 3 months of life. A girl with autosomal recessive chronic granulomatous disease presented at 18 months of age with regional lymphadenitis. All three patients with chronic granulomatous disease had positive tuberculin reactions and died from infections other than BCG.