A retrospective radiological study was performed on 23 cases of pleural mesothelioma. Nineteen of the cases were males and four were females. Eleven cases had histories of exposures to asbestos (1332214) of 2, 5, 10 (three cases), 14, 15, 16, 22, 24, and 76 years, respectively, suggesting that the accepted latent period between exposure and tumor development is probably excessive. Seven others had lived in areas where mining and milling of asbestos took place (calcific areas), in which x-rays have demonstrated a large number of people with calcified pleural plaques. Four other cases had no history of exposure, but one of the four had radiological evidence of asbestotic fibrosis. Fourteen cases presented with pleural effusions as the main x-ray feature. Three of them were associated with extrathoracic soft tissue masses. In six cases a lobular pleural tumor was evident with no obvious radiographic change to suggest an associated pleural effusion. Hilar masses were found in six cases and were on the same side as the pleural tumor. Two cases had round lung lesions on the tumor side. Three cases had extrathoracic soft tissue masses. One patient had a hydropneumothorax, and the pleural tumor was easily visible. Signs of asbestosis were: parenchymal lung changes (five cases), noncalcified pleural changes on the side opposite the lesion (seven cases), pleural calcification (two cases). The author concludes that if there is radiological evidence of asbestos exposure, a pleural effusion indicates a significant complicating condition such as malignancy or tuberculosis, and a hilar mass must also be considered ominous. Pleural calcification and lung fibrosis are not closely associated with development of mesothelioma.