Allergic bronchopulmonary aspergillosis (ABPA) is a complex disease occurring in 1-2% of patients with asthma involving hypersensitivity to Aspergillus species. The diagnosis is made correlating clinical history and supporting serologic tests. Over many years various serologic tests have been used to both diagnose and follow disease activity. Initial serology from patients with all four positive tests (total serum IgE, IgE and IgG antibody indices, serum precipitins to Aspergillus fumigatus) were compared with the patients' most recent serology. The total serum IgE, IgE antibody index and serum precipitins had the most initial positive tests which stayed positive throughout treatment. The IgG antibody index was the most inconsistent. There were no significant differences between all four tests. We concluded that all four serologic tests are important in the diagnosis of ABPA.