The pathologic findings from biopsy specimens from 9 patients with postvaccination bacille Calmette-Guérin (BCG) infection are presented. The patients were vaccinated with BCG during the first 2 days of life. Four patients had normal immunity and 5 patients were immunocompromised. The pathologic findings in both groups were different. Biopsy specimens from patients with normal immunity showed multiple epithelioid granulomas and Langhans giant cells with or without suppuration. Caseous necrosis was minimal. Ziehl-Neelsen stain for acid-fast bacilli showed a few bacilli in 2 cases and was negative in the remaining 2 cases. Biopsy specimens from the second group of patients, who were immunosuppressed, consisted mainly of skin and subcutaneous tissue. These revealed diffuse infiltrates of histiocytes with plump nuclei and abundant "dirty" grayish cytoplasm, which was full of numerous acid-fast bacilli. The clinical course for the 2 groups also was different. Patients with normal immunity generally recover completely, spontaneously or after excision of the suppurative lymph node and usually do not require antibiotic chemotherapy. In immunosuppressed patients, disseminated BCG infection, which may prove fatal, may develop. These patients should receive a full course of antituberculous chemotherapy and, in addition, treatment of the underlying immunologic disorder.