The clinical, radiographic, and pathologic findings in 82 patients with congenital bronchial atresia (CBA) have been reviewed, and we have discussed 4 additional cases. Most patients are asymptomatic and come to attention because of abnormal radiographic findings of a round or lobulated perihilar, solid, or cystic mass--the mucoid impaction sign. Typically, the region distal to the mass is hyperinflated. Recently, computed tomography has been shown to be diagnostic and its use obviates the need for other more complex imaging modalities or surgical exploration. Excisional surgery has been performed to preserve lung function in younger patients, because of lack of familiarity with the entity or, as in 2 of our cases, to prevent recurrent infections. Pathologic findings include a cystic, blindly terminating, mucus-filled bronchocele without connection to the main bronchial tree, but with normal subsequent generations of bronchi. Distally there is noncollapsible hyperinflation of the corresponding lung segment or lobe as the result of collateral ventilation from the surrounding lung. The anomaly is the result of an insult to the growing bronchial tree in early development. The differential diagnosis most often includes allergic bronchopulmonary aspergillosis, but cystic bronchiectasis, bronchogenic cysts, and intrapulmonary sequestration should also be considered. Unusual features in our 4 cases included recurrent pulmonary infections in 2 patients and thoracic cage asymmetry in 1.