BACKGROUND Medical thoracoscopy, in the educated fingers of a pulmonologist, is a secure and powerful process for the diagnosis and treatment of many pleural diseases. If the centres for thoracoscopy are available, thoracoscopy should be carried out on those undiagnosed sufferers due to its excessive sensitivity in malignant and tuberculous pleural effusions. That is why the ultimate decade witnessed an interest in thoracoscopy as a diagnostic device for pleural diseases. In the existing study, we wanted to describe our experience with the function of thoracoscopic biopsy in patients who underwent thoracoscopy for diagnostic purposes. METHODS The study protocol and ethical approval were taken by the Institutional Review Board for human studies of B. J. Medical College, Gujarat. It was a prospective study conducted in the Department of Pulmonary Medicine, B. J. Medical College, Ahmedabad, between July 2014 and November 2016. 39 patients who underwent medical thoracoscopy for undiagnosed pleural effusions were enrolled in this study. Undiagnosed pleural effusion was defined as failure to achieve a diagnosis by initial pleural fluid analysis including pleural fluid adenosine deaminase (ADA) levels and at least three pleural fluid analyses negative for malignant cells. Diagnostic pleural fluid aspiration was done to obtain pleural fluid specimens. RESULTS In the present study with the help of thoracoscopy, 36 (92.31 %) patients were diagnosed successfully while only 3 patients remained undiagnosed. In the present study, on thoracoscopic examination 21 (53.85 %) patients had pleural nodules, 5 (12.82 %) patients had pleural thickening, 5 (12.82 %) patients had pleural plaquelike erythema. The remaining patients had other uncommon findings e.g. nonspecific pleuritis 3 (7.69 %). CONCLUSIONS Among all the patients with undiagnosed exudative pleural effusion, irrespective of smoking status which fails to respond to conventional medical management, diagnostic thoracoscopy should be considered as early as possible. The diagnostic yield of thoracoscopy for pleural pathology remains very high (92.3 %). KEYWORDS Diagnosis, Malignant Pleural Effusion, Thoracoscopy.