The inhalation of Aspergillus fumigatus (Af) spores liberated from a municipal leaf compost site led to the development of allergic bronchopulmonary aspergillosis (ABPA) in a patient living in the area. The patient developed characteristic symptoms of ABPA and demonstrated precipitins against Af antigens in his sera. The potential hazard caused by uncontrolled composting resulting in the dissemination of several allergenic fungi and other microbes is exemplified by this case.