Mycobacterium tuberculosis bacteremia is being reported more frequently in patients with human immunodeficiency virus, type 1 (HIV-1) infection. We report 9 patients with bacteremia due to M. tuberculosis and HIV infection who were identified over a 36-month period. Of the 9 patients studied, 8 were male, 8 were black, 6 were born in Haiti, 3 were homeless, 2 were intravenous drug users, and 1 was homosexual. At the time of diagnosis, 3 patients had the acquired immunodeficiency syndrome (AIDS) and 5 patients had CD4 lymphocyte counts less than or equal to 170 cells/mm3, indicating marked immunodeficiency. All 9 patients presented with temperature greater than 38.3 degrees C, 5 (50%) had abnormal chest roentgenogram on admission, and each of the patients tested had elevations of at least 2 liver function tests. Eight patients (80%) had M. tuberculosis isolated from sputum or other body fluids and tissues. All blood isolates of M. tuberculosis were identified from Dupont Isolator tubes. Antibiotic-resistant isolates of M. tuberculosis were cultured from 3 of the 6 patients born in Haiti. One patient died before diagnosis and received no antimycobacterial therapy; 7 of the remaining 8 patients appeared to respond to treatment. Our data, and a review of the literature, suggest that bacteremia due to M. tuberculosis is becoming more frequent, and that blood cultures may be helpful in establishing or confirming a diagnosis of tuberculosis in patients with HIV-1 infection.