Rapid clinical improvement of allergic bronchopulmonary aspergillosis (ABPA) is usually noted with corticosteroid therapy. We report a case of ABPA that developed in patient who was being treated with prednisone on a maintenance basis for severe asthma. Recovery from the short-term episode of ABPA was protracted and required higher doses of corticosteroids for control of the syndrome than usually necessary. It is suggested that corticosteroids do not prevent the development of ABPA, and that patients who develop the syndrome while on corticosteroids may have a protracted course with poor response to the usually effective doses of corticosteroids.