We report here on a 36-year old, HIV-positive patient, who was sent to hospital with an anal fistula. A short time later during the course of an extensive diagnosis the anal fistula was recognized as an extrapulmonary manifestation of a miliary tuberculosis stemming from an immunodeficiency syndrome. A rapid conversion of the sputum, a normalization of the radiological findings and the absence of relapse are the results of the classic systemic fourfold therapy with myambutol, isoniazid, rifampicin and streptomycin. The danger of overlooking the fact that an anal fistula can be the clinically primary manifestation of a tuberculosis and the problems of a mixed infection within the scope of the acquired immunodeficiency syndrome are discussed. Tuberculosis as a frequent complicating infection of HIV-positive patients--often diagnosed some time before the AIDS-infection as in our patient--can be successfully cured by a high dose of intravenous pharmacotherapy, even when additional complications (parasitic stomatitis, increasing deterioration of the immunological parameters) are present. In order to show the large spectrum of the problems involved in the diagnosis, the therapy and the course of the active acquired immunodeficiency syndrome, we have focused here on the detailed description of the case report.