BACKGROUND: Sarcoidosis is a systemic granulomatous disease of unknown aetiology. Pleural effusion is very rare in sarcoidosis. In cases with pleural effusion, usually other etiologic factors such as tuberculosis, heart failure, renal failure and malignancy should be considered. METHODS: We retrospectively reviewed the records of 512 sarcoidosis patients followed up at Ceraphasa Medical Faculty, Internal Medicine-Respiratory Disease Department, Turkey. RESULTS: Only four patients with pleural effusion were documented, in three of them it was due to tuberculosis. The patients were negative for microbiological tests regarding tuberculosis and tuberculin tests as well, when the diagnosis of sarcoidosis was made. With the occurrence of effusion tuberculin tests became positive. Acid-fast bacilli (AFB) was cultured in pleural fluid and biopsy materials. After addition of antituberculosis therapy, pleural effusion regressed in all the three cases. CONCLUSIONS: In a sarcoidosis patient with no active disease activity who present with a pleural effusion, if other causes are excluded, it is advisable to start anti-tuberculosis therapy since sarcoid pleural effusion is a rare form of disease occurring at advanced stage of disease. Moreover, corticosteroid therapy renders patients susceptible to tuberculosis. Tuberculin conversion could be a clue to diagnosis in these patients.