Malignant pleural mesothelioma, a rare and usually fatal neoplasm that is associated with asbestos exposure, is being encountered with increasing frequency. Pretreatment CT findings from 50 patients with malignant pleural mesothelioma are illustrated. Pleural thickening was found in 46 (92%) of the 50 patients, thickening of the pleural surfaces of the interlobar fissures in 43 (86%), pleural calcifications in 10 (20%), and pleural effusions in 37 (74%). The volume of the involved hemithorax varied appreciably. Contractions of the involved hemithorax was noted in 21 (42%) of 50 patients and contralateral mediastinal shift in seven (14%). Disease beyond the parietal pleura was found in the chest wall (nine patients), mediastinum, lymph nodes, and diaphragm.