In this report 21 patients in whom tuberculosis was the primary cause of death, but which was not diagnosed until necropsy, are reviewed. Of the 21 deaths, 11 were due to pulmonary tuberculosis and 10 to miliary tuberculosis. Proper evaluation of the following factors might have led to the correct diagnosis in many of the patients: A family history of tuberculosis, prior pleurisy, a gastrectomy, diabetes mellitus or end-stage renal failure; all can be associated with an increased incidence of tuberculosis. A negative tuberculin skin reaction does not exclude the presence of active tuberculosis. In the search for Mycobacterium tuberculosis, the examination of just one or two sputum specimens is not an adequate bacteriologic investigation. A positive gastric smear can have diagnostic importance. Ascitic fluid findings can be characteristic of tuberculous peritonitis. A negative bone marrow aspirate for acid-fast bacilli does not exclude miliary tuberculosis. Significant anemia, high fever and leukopenia increases the possibility of tuberculosis. The persistence and/or progression of lung infiltration, irrespective of supposedly specific antibiotic therapy, strongly suggests tuberculosis. Miliary tuberculosis can present as an adult respiratory distress syndrome. All but one patient in this series had fever. the failure to diminish the pyrexia believed due to specific lung infections with presumably effective antibiotics, and the inability of therapy to control other conditions thought to cause the fever indicate the presence of tuberculosis. Tuberculosis, especially miliary disease, should be considered as a possible etiology of fever of unknown origin. If the diagnosis of tuberculosis is highly suggestive, even without bacteriologic confirmation, a therapeutic trial of antituberculosis drugs should be given.