Diagnostic thoracoscopy in patients with pleural effusion of unclear origin mostly provides the correct diagnosis. Results from published reports of previous researches are not uniform. In 47 male and 20 female patients with pleural effusion of unknown etiology, after receiving negative results obtained from cytological finding of pleural effusion and percutaneous needle biopsy, thoracoscopy with biopsy of one or both pleurae was performed. Procedure was done in local anesthesia using Stortz rigid thoracoscope. In 37 patients with malignant disease (primary or metastatic) diagnosis was confirmed histopathologically in 31 patient (81.12%). In 27 patients with inflammatory pleural disease diagnosis was confirmed histopathologically in 22 patients (81.4%). Among 11 patients with specific pleural effusions, tuberculosis was confirmed in 10 (90.91%). Normal finding in cases of spontaneous pneumothorax and pulmonary embolism was taken as a positive result. Total number of positive findings was 55 (82.10%). In one patient, the third spontaneous pneumothorax was the indication for thoracoscopy, and after numerous bullae were seen during the procedure, talcum powder pleurodesis was done. In four patients low intensity subcutaneous emphysema occurred one day after thoracoscopy. It can be concluded that thoracoscopy in local anesthesia out of the operating room is good and practical method for solving the unclear pleural effusions, with neglectable rate of complications.