The possibility of tuberculous pleuritis should be considered in every patient with an undiagnosed pleural effusion, for if this diagnosis is not made the patient will recover only to have a high likelihood of subsequently developing pulmonary or extrapulmonary tuberculosis Between 3% and 25% of patients with tuberculosis will have tuberculous pleuritis. The incidence of pleural tuberculosis is higher in patients who are HIV positive. Tuberculous pleuritis usually presents as an acute illness with fever, cough and pleuritic chest pain. The pleural fluid is an exudate that usually has predominantly lymphocytes. Pleural fluid cultures are positive for Mycobacterium tuberculosis in less than 40% and smears are virtually always negative. The easiest way to establish the diagnosis of tuberculous pleuritis in a patient with a lymphocytic pleural effusion is to generally demonstrate a pleural fluid adenosine deaminase level above 40 U/L. Lymphocytic exudates not due to tuberculosis almost always have adenosine deaminase levels below 40 U/L. Elevated pleural fluid levels of gamma-interferon also are virtually diagnostic of tuberculous pleuritis in patients with lymphocytic exudates. In questionable cases the diagnosis can be established by demonstrating granulomas or organisms on tissue specimens obtained via needle biopsy of the pleura or thoracoscopy. The chemotherapy for tuberculous pleuritis is the same as that for pulmonary tuberculosis.