The purpose of this paper was to quantitate the distribution and severity of computed tomography (CT) and radiographic findings in patients with allergic bronchopulmonary aspergillosis (ABPA), probable ABPA, and asthmatic controls. Chest radiographs and high-resolution CT images were evaluated in 19 patients with documented ABPA and 18 asthmatic controls. Ten patients with probable ABPA were also evaluated. On CT examination 17 patients (89%) with ABPA had central cystic or varicoid bronchiectasis in at least one lobe. One patient had no evidence for bronchiectasis. Three asthmatic patients (17%) had findings of cylindrical bronchiectasis. All 10 patients with probable ABPA had evidence of bronchiectasis on high-resolution CT (HRCT). The majority of patients with ABPA have diffuse disease at the time of diagnosis, manifested by central cystic and/or varicoid bronchiectasis in four or five lobes. Evaluation with HRCT can facilitate a diagnosis of ABPA and probable ABPA, allowing for earlier treatment which may prevent progression to fibrosis.