Between October 1983 and April 1987, 20 patients with malignant mesothelioma underwent computed tomography scans of the chest and upper abdomen to evaluate the extent of disease before treatment. Twelve of these 20 patients deemed to have some potential for long-term survival had scans performed every 3 months after operation to help detect recurrent disease. Anatomic correlation of computed tomography scan findings was available in all 20 patients. The limitations of computed tomography in initial evaluation were its difficulties in assessing (1) chest wall involvement (nine patients), (2) mediastinal lymph nodes (four patients), (3) transdiaphragmatic extension of tumor (four patients), and (4) peritoneal studding and solid organ metastases less than 2 mm in size (one patient). Computed tomography was helpful in detecting recurrent disease in the 12 patients having long-term follow-up. In six of eight cases with histologically proved recurrence, computed tomography detected tumors from 1 to 8 months before the onset of signs or symptoms. Although computed tomography is known to provide far more information about the extent of disease than plain radiographs, it remains an imperfect tool for the staging of disease in patients with malignant mesothelioma. Despite its limitations, computed tomography is probably the most accurate way to provide follow-up for patients during treatment.