From January 1990 to July 1998, twelve patients (10%) among 120 patients with human immunodeficiency virus infection who were hospitalized in the Veterans General Hospital-Taipei, were proved to have Mycobacterium tuberculosis infection. The mean age of these patients was 38 years, range: 25-62 years. All patients studied were in the advanced stage of acquired immunodeficiency syndrome (AIDS) with a mean circulatory CD4 lymphocyte count of 21/microL (range: 0-64/microL) and a much higher HIV viral load at initial diagnosis of M. tuberculosis infection. Because of no significant difference in the HIV viral load between patients with active pulmonary tuberculosis and those with extrapulmonary tuberculosis in this study, dissemination of M. tuberculosis did not correlate directly with a high HIV viral load, but was possibly related to the virulence of the organism itself. Chest radiographic findings at initial diagnosis of pulmonary tuberculosis were variable and atypical. Most patients (62.5%) presented with a primary pattern (lower lobe or diffuse infiltrates), while hilar lymphadenopathy was noted in more than half of the patients and cavitation was less common (only one patient). Ten patients (83.3%) had extrapulmonary involvement; the most common site being the lymph nodes. Most patients with classic drug-sensitive tuberculosis responded well to conventional standard regimens of anti-tuberculosis therapy. Since tuberculosis is transmittable, treatable, and possibly preventable, moreover the clinical presentation of tuberculosis in the patients with AIDS may be atypical and unusual, clinical physicians must keep an alert dealing with these patients for early identification and early treatment.