A patient with allergic bronchopulmonary aspergillosis who developed a cavitary lung lesion suggestive of neoplasm is presented. At thoracotomy an aspergilloma was found. Although coexistence of these two forms of aspergillosis has been reported, the brief history of preceding asthma and the rapid development of the aspergilloma in the absence of typical roentgenographic features are unusual. Aspergilloma should be considered when a patient with allergic bronchopulmonary aspergillosis develops a cavitary pulmonary lesion.