In the present study, Interleukin-6 (IL-6), Gamma in-terferon (•yIFN) and adenosine deaminase (ADA) were studied in exudative pleural effusion from tuberculous, malignant and postpneumonic origin and transudative pleural effusion of systemic origin to determine their di¬agnostic value and whether either or all of them could be helpful in differential diagnosis of origin of pleural effusion. The three markers were detectable in all effusions with a significant high levels in exudative as compared to transudative effusions(p value less than 0.001). Also no significant difference in their levels has been noticed in tuberculosis effusion as compared with postpneumonic effusions .It is concluded that IL-6,y IFN andADA levels in pleural effusion are sensitive parameters to differentiate exudate from transudate pleural effusion while y INF and ADA can only differentiate exudative pleural effusion of different etiology.