BACKGROUND An undiagnosed exudative pleural effusion is often a difficult diagnostic dilemma that needs further histological study for a definitive etiological diagnosis. Video assisted rigid thoracoscopy is a minimally invasive procedure with a minor morbidity and mortality risk that could resolve this problem. METHODS Between January 2010 and December 2011, we performed thoracoscopy in 26 patients for diagnosis of undiagnosed exudative pleural effusion. Clinical and paraclinical data of patients were collected prospectively and analyzed. RESULTS Sole pleural effusion was the most common CT scan finding seen in 17 (65.4%) patients. Thoracoscopy was diagnostic in 24 patients (92.3%). The pathologic findings were carcinoma (46.2%), tuberculosis (30.8%) and chronic inflammation without a definitive microbiologic culture (15.4%). Surprisingly mean ADA level in the tuberculosis group was in normal range. No mortality or complication related to our operation was observed. CONCLUSIONS Video assisted thoracoscopy is a minimally invasive procedure with a high definitive diagnostic accuracy in the evaluation of tuberculosis and malignant pleural effusions. Pulmonologist should refer these patients sooner to decrease the waiting period of diagnosis and treatment of such conditions.