In the last decade, the incidence of tubercular disease in Italy has increased. The age-groups 20-39 and 65-80 years are the ones mainly involved. However, compared to younger age-groups, the presentation of the disease in the elderly is often poorly characteristic, and for this reason a correct diagnosis is often delayed. We describe the case of an elderly man who came to our observation for the persistence of fever (since 20 days, mainly in the evening) associated with decreased leukocyte and platelet counts and with progressively worsening of his general conditions. The laboratory data and bacteriological and instrumental examinations were not diagnostic, whereas a bone marrow biopsy provided evidence of tubercular granulomas. The confirmation of the diagnosis of disseminated tuberculosis has been supplied subsequently with cultural test of smear. The patient's conditions rapidly improved after antitubercular treatment. This case underlines the relevance of bone marrow biopsy in the diagnosis of fever of unknown origin in the elderly, especially when the serious clinical conditions of the patient do not allow one to wait for the results of the cultural examination.