Allergic Bronchopulmonary Aspergillosis (ABPA) is characterized by recurrent pulmonary infiltrates that can result in central bronchiectasis and bronchiolitis obliterans especially if there is a lack of recognition and treatment. The incidence of ABPA is 1-2% in patients with persistent asthma and approximately 7% (range 2-15) in patients with cystic fibrosis. The diagnostic criteria are useful in that there is no single test (with the exception of central bronchiectasis in patients with asthma) that identifies ABPA. The differential diagnosis of ABPA includes many conditions including chronic eosinophilic pneumonia, Churg Strauss Syndrome, Hyper-IgE Syndrome, persistent asthma with lobar collapse, and cases of parasitism. The most useful laboratory assays in patients who have immediate cutaneous reactivity. to Aspergillus mixes or A. fumigatus are total serum IgE concentration, elevated serum IgE-A.fumigatus and serum IgG-A.fumigatus. Prednisone remains the drug of choice yet need not be administered indefinitely.