INTRODUCTIONPleural effusion is the abnormal accumulation of fluid in the pleural space. It can be transudate or exudates and Light's criteria help to differentiate them.1 Exudative pleural effusion is a commonly encountered clinical scenario among both respiratory and non-respiratory specialists. In humans, approximately 75% of the cells in the pleural fluid are macrophages, 25% are lymphocytes and mesothelial cells, neutrophils and eosinophils accounting for less than 2% each.2 The precise pathophysiology of fluid accumulation vary based upon ABSTRACT Background: Undiagnosed exudative pleural effusion is a commonly encountered clinical scenario, which requires further evaluation. This study was aimed to analyze the diagnostic yield and complications of three proceduresBronchoscopy, closed (Abram's) pleural biopsy and medical thoracoscopy. Further, this study assessed whether combining closed pleural biopsy with bronchoscopy can be a substitute for medical thoracoscopy. Methods: An observational study was conducted among people with undiagnosed exudative pleural effusion. Initially, closed pleural biopsies were performed with Abrams needle and multiple tissue fragments were taken through the incision and the samples were sent in formalin to the laboratory for histopathology examination. For thoracoscopy, a cannula of 10 mm diameter with blunt trocar was inserted into the pleural cavity and semi rigid thoracoscope was introduced through the trocar. Bronchoscopy was performed 48 hours after thoracoscopy. Sensitivity, specificity and positive and negative predictive values were calculated and compared. Results: Out of 25 people, 14 were diagnosed to have malignancy and 7 were diagnosed tuberculosis. The overall sensitivity of the three procedures were 28.5% for closed pleural biopsy, 14.2% for bronchoscopy, 95.2% for medical thoracoscopy, 42.8% for the combined pleural biopsy and bronchoscopy. The complication rate was lowest for bronchoscopy (4%), followed by medical thoracoscopy (8%) and closed pleural biopsy (16%). Conclusions: Medical thoracoscopy is a comparatively safe procedure which has got the highest sensitivity for the diagnosis of undiagnosed exudative pleural effusions. Bronchoscopy combined with closed pleural biopsy, the diagnostic yield was increased (than that of individual yield), but cannot be a substitute for medical thoracoscopy.