The clinical features of tuberculous pleurisy frequently resemble an acute, bacterial infection, particularly in younger adults. In 71 patients a diagnosis of tuberculous pleurisy with effusion was established by needle biopsy of the parietal pleura. The tuberculous etiology may be suspected when (1) pleural pain occurs prior to the onset of cough, (2) the cough fails to produce purulent material, (3) the white blood cell count is not increased, and (4) the pleural fluid is clear (particularly if it is green-tinged).