Radiographs and computed tomography (CT) scans of the chest were reviewed for 10 patients with pathologically proven Wegener's granulomatosis. The CT scans revealed multiple pulmonary nodules in seven patients and a single nodule in one. The nodules ranged in diameter from 2 mm to 7 cm, and most had irregular margins. All of the nodules larger than 2 cm in diameter showed evidence of cavitation in the CT scans. Additional CT findings included associated areas of consolidation (in two patients), pleural thickening (in two) and pleural effusion (in two). Chest radiographs were available for eight patients, and the CT scans contributed information additional to that available from the radiographs for seven of these. In one patient lung nodules were visible in the CT scans but could not be distinguished from surrounding areas of consolidation in the chest radiographs. CT revealed additional nodules in five of the six patients in whom multiple nodules were seen in chest radiographs and in one of these also revealed cavitation tht was not visible in plain radiographs. CT excluded the possibility of a nodule that was suspected from the chest radiographs in a patient who had been treated previously for Wegener's granulomatosis. The authors conclude that Wegener's granulomatosis is characterized in CT scans by multiple nodules with irregular margins and by cavitation in nodules larger than 2 cm in diameter. CT may also demonstrate nodules and cavitation not apparent in radiographs.