Allergic bronchopulmonary aspergillosis (ABPA) has been recognized increasingly in the past few years. In minimal disease, plain chest films may be insensitive. Early detection of pulmonary involvement may help prevent irreversible damage to the lungs and bronchi. Bronchography, while both sensitive and specific, is not without hazard, particularly to the asthmatic patient. We evaluated the usefulness of linear tomography in confirming ABPA prior to initiation of corticosteroid therapy. We find that tomography is a simple, noninvasive instrument for detecting the presence of or proving the absence of the earliest manifestations of ABPA.