Tuberculosis is the most frequent infectious complication of AIDS and HIV infection in countries where che prevalence of tuberculous infection is high. HIV infection is the strongest risk factor for developing tuberculosis in individuals infected removly or recently with tubercle bacilli. An increased incidence of tuberculosis has been already documented in several African countries with a high prevalence of both tuberculous and HIV infections (Tanzania; Malawi). The increase in the incidence of tuberculosis is mainly due to the depression of cellular immunity caused by HIV infection in subjects infected with M. tuberculosis. The occurrence of tuberculosis in HIV-seropositive persons is more frequent in those remotely infected than in those recently infected or reinfected with M. tuberculosis. In developed countries; HIV infection will cause tuberculosis in only a relatively small number of persons; since the prevalence of tuberculosis infection is low in the age group up to approximately 45 years. HIV infection will; therefore; not substantially increase the number of tuberculosis cases