We tabulated the computed tomographic (CT) findings in 14 consecutive patients who had proven malignant pleural mesotheliomas and were studied over a 3-year period. We also staged the disease in these patients, all of whom were men, aged 40-75 years (mean, 59), and had been exposed to asbestos at work. Common presenting symptoms were shortness of breath or chest pain. Pleural thickening was found on the side of the tumor in all of the patients, characterized as nodular and circumferential (6/14 cases), plaque-like (4/14), or strictly nodular (4/14) in appearance. In addition, 86% of the patients demonstrated contralateral pleural thickening, but these lesions did not prove to be tumor deposits. Other common CT findings in the involved hemithorax included: pleural effusions (79% of cases), lung parenchymal disease (79%), decreased hemithorax size (62%), and pleural calcification (50%). Before the chest scans were performed, 13 patients were felt to have Stage I disease and one to have Stage IV. The CT information revised these opinions: four of the Stage I patients were assigned to Stage II (on the basis of chest wall involvement or enlarged hilar/mediastinal lymph nodes). Therapy was altered in these four cases. In two patients pericardial thickening was seen, but it was not possible to determine if this was due to tumor involvement. We conclude that CT can identify several abnormalities that are commonly associated with mesotheliomas. By demonstrating lesions not detectable on conventional imaging studies, CT may alter staging and therapy in many patients with this disease.