Frequency and risk of tuberculosis were studied among a large group of HIV-infected patients (n = 2556), 869 of whom had AIDS, over a period of ten years (February 1982 through February 1992) at the University Hospital Frankfurt. A total of 148 (5.8%) out of 2.556 patients had tuberculosis. With increasing immunodeficiency, the frequency of tuberculosis rose. The rate of tuberculosis in post-mortem was even higher, i.e. 17.3%. I.v. drug-addict AIDS patients were inflicted with 18.5% considerably more often than homo-/bisexual patients with 12.3%. The same holds true with 25% of tuberculosis infections for AIDS patients from endemic areas as compared with 13% for patients from countries with lower tuberculosis incidence. 18% of patients contracted tuberculosis already at > 200 CD4-positive cells/microliters before AIDS manifestation. Coming from endemic areas, drug addiction and lower number of T-cells signify a high risk for HIV-infected patients to acquire a post-primary or primary tuberculosis, respectively. HIV-infected patients represent a relevant danger of infection for partners and health-care personnel. In contrast to the United States, no increase in the tuberculosis incidence, except for some areas like Frankfurt, has been noted. Preventive measures, which include the IHN prophylaxis for patients with T-cell counts < 150/microliters, should be discussed.