Narrow section (3 mm width slices every 10 mm) computed tomography on an Elscint 2002 scanner and plain chest radiography were performed in 10 patients with allergic bronchopulmonary aspergillosis. No patient was experiencing an acute exacerbation. The investigations were reported separately and in random order. Bronchiectasis was reported in 31 of 60 lobes on computed tomography compared with only 15 on plain chest radiographs. Computed tomography was also more sensitive for proximal bronchiectasis detected in 16 lobes compared with only in 10 on plain chest radiographs. Serial computed tomography may allow earlier identification of progression of lung damage in patients with allergic bronchopulmonary aspergillosis and so help in planning treatment.