The concentrations of total IgG, complement C3 and circulating immune complexes (CIC) were studied in 15 patients with allergic bronchopulmonary aspergillosis (ABPA) during remission and compared with those of 10 matched controls. The concentrations of complement and circulating immune complexes were similar to those of the controls but 33% of patients with ABPA in remission still had circulating immune complexes, mainly of IgG. Even so, the concentrations of IgG were significantly higher in patients during remission compared to controls but were lower than those observed during the acute stage of ABPA.