Mesothelioma is a rare disease but its incidence is rising. Diagnosis is still difficult but has been improved by immunohistochemical techniques and panels of pathologists. At the present time thoracoscopy is the most sensitive method for diagnosis of mesothelioma and a good alternative to thoracotomy. The main indication for thoracoscopy is unexplained pleurisy that cannot be diagnosed by needle biopsy. Thoracoscopy allows diagnosis in 95% of cases. Pleural ultrasound can be useful for diagnosis of limited pleurisy without multiple radiation exposure. Thoracoscopy is usually performed under light general anesthesia using a rigid endoscopic system. If possible, pneumothorax should be induced the day before the procedure to allow better assessment of the entry route and prevent adherences or symphysis. Tolerance of thoracoscopy is excellent. Thoracoscopy allows not only complete visualization of the pleural cavity including the diaphragmatic visceral pleura and the lung but also multiple biopsies. In early stage disease, thoracoscopy permits distinction of patients with stage Ia (involvement confined either the parietal or diaphragmatic pleura and purely inflammatory aspect in 50% of cases) from patients with stage Ib (involvement of the visceral pleura). Median survival is 28.3 months for stage Ia versus 10 months for stage Ib. Endoscopic observation enables accurate staging of tumor involvement which is an important prognostic finding and is an essential technique for early diagnosis of mesothelioma.