We prospectively studied the effect of human immunodeficiency virus (HIV) infection on the presentation and outcome of tuberculosis. A total of 216 patients with tuberculosis were identified; 162 (75%) of these patients were tested for antibodies to HIV; 92 (57%) were seropositive. The patients who were seropositive for HIV were more likely to be male and Hispanic and to have been homeless or incarcerated. Eighty-one percent of these patients had CD4 lymphocyte counts of < or =200/mm3. The seropositive patients had extrapulmonary tuberculosis more often than did the seronegative patients (odds ratio [OR], 2.3; 95% confidence interval [CI], 1.2-4.8). Smears for acid-fast bacilli were positive more often for non-HIV-infected patients with pulmonary tuberculosis (74.5%) than for HIV-infected patients (54.3%) [OR, 2.46; 95% CI, 1.01-6.02]-even those with focal or cavitary disease. A delay in initiating therapy was associated with in-hospital mortality: the median time from admission to the start of treatment was 4 days for patients who survived and 15 days for those who died (P = .02). The median survival was 22.7 months for HIV-infected patients who did not die during the initial hospitalization. Factors independently associated with reduced rates of survival included the severity of immunodeficiency, nonuse of directly observed therapy, infection due to drug-resistant Mycobacterium tuberculosis, and a history of injection drug use.