Pleural effusion can result from a very wide range of disease processes. In most instances, the cause of the effusion becomesapparent from the associated clinical circumstances, diagnosticthoracocentesis, and/or percutaneous pleural biopsies withcultures, cytological and histological examination.The criteria established by Light et al., 1972; pleural fluidprotein > 3gm/dL, pleural fluid to serum protein ratio > 0.5gm/dL, pleural fluid LDH concentration > 200I/L and pleuralfluid to serum LDH ratio > 0.6I/L have been used widely forthe differentiation of exudative pleural effusion cases fromtransudative pleural effusion cases.