The frequency of malignant pleural mesothelioma has increased greatly in the past three decades; it is a tumor of great clinical, epidemiologic and therapeutical interest. Therapy should not be started before the tumor has been correctly diagnosed and staged with thoracoscopy and computed tomography (CT) which have replaced plain chest radiography. To help optimize the combination of these techniques, the authors report on their experience in 37 patients examined with conventional radiology and then with thoracoscopy. In 26 patients with CT findings of malignant pleural mesothelioma, the authors compared thoracoscopy and CT findings in the assessment of neoplastic spread to the parietal (stage IA) and/or visceral (stage IB) pleura. CT appears to be the technique of choice after plain chest radiography: if the suspected malignant pleural mesothelioma is classified as stage II, III or IV, thoracoscopy should be used only for histologic confirmation. Conversely, in stages IA and IB, thoracoscopy--besides histology--should be used to confirm malignant spread to the visceral pleura.