RESUMEN
Fifty cases of lymphocytic exudate of the pleura and peritoneum were studied to determine the cause. Though tuberculosis was suspected provisionally in the majority, isolation of M. tuberculosis was rare and other investigations proved more helpful. Histological examination of material obtained by laparoscopy was the most reliable method followed by pleural biopsy, especially if it was an open one. This procedure has the invaluable advantage of a rapid diagnosis without the need to await the results of culture. The specific gravity and the cell count were of help to determine the exudative nature of the fluid. The protein content, the lactic dehydrogenase value of the fluid and its ratio to the blood value were more useful in determining a possible aetiology. A definite diagnosis of tuberculosis was made in 21 cases. A further 13 cases (3 with highly suggestive histological appearances) were judged to be tuberculosis in view of their suggestive history and excellent response to specific antituberculosis chemotherapy. Eleven cases proved to be due to malignant disease.