Tuberculosis has now been well documented as a complication of infection with human immunodeficiency virus (HIV), but no studies concern patients requiring admission to the ICU. We report 12 cases of severe disseminated tuberculosis in patients who were seropositive for HIV. Eight patients had diffuse pulmonary involvement responsible for acute respiratory failure, 7 of whom required mechanical ventilation. Four developed septic shock, and in 3 blood cultures were positive for M. tuberculosis. Four patients had central nervous system involvement, with coma requiring mechanical ventilation 3 times. Rapid diagnosis was permitted in 10 patients by acid-fast smears of pulmonary specimens (8 patients) and/or tissue biopsies (4 patients). Seven patients died despite intensive therapy; autopsy was performed in 4 patients, showing disseminated tuberculosis. On the basis of this report, tuberculosis in HIV infection may present as an overwhelming systemic disease and thus requires an aggressive diagnostic and therapeutic approach.