A characteristic thoracoscopic picture of a granular parietal pleural surface was found in nine patients with rheumatoid pleurisy. Characteristic changes could be identified histopathologically in material obtained by biopsy. The rheumatoid pleural effusion resolved within an average of 14 months and no serious complications developed after the pleurisy. It is concluded that in rheumatoid pleural effusion a positive diagnosis can be made by thoracoscopy, preferably supported by the identification of microscopic structural changes in the parietal pleura.