One of the most common complication of primary tuberculosis in India is exudative pleural effusion. Adenosine deaminase (ADA) is an enzyme produced by activated T- lymphocytes in response to the mycobacteria tuberculosis infection. ADA levels in pleural fluid will be comparatively higher than the serum levels suggesting the local synthesis of ADA by activated T-lymphocytes. Thus the estimation of ADA in tubercular pleural fluid helps in the diagnosis of tubercular pleural effusion. The objective of this study was to find out the role of ADA levels to differentiate tuberculous and non-tuberculous exudative pleural effusions of other aetiologies. Thestudy comprises of 50 randomly selected cases, having of pleural effusion of different aetiologies and are admitted in the medical ward at a tertiary care hospital. The study found that pleural fluid ADA levels were significantly higher (p<0.001) in tuberculous exudative pleural effusions when compared with non-tuberculous exudative pleural effusions. Hence, determination of ADA level in exudative pleural effusions is cost effective, rapid and simple procedure which should be considered for routine investigation of patients with pleural effusion, especially in a country like India where tuberculosis still overwhelmingly out numbers, the other causes of lymphocytic pleural effusion.