Itraconazole is a new orally active antifungal triazole with impressive activity against Aspergillus spp. Six patients with allergic bronchopulmonary aspergillosis (ABPA), aged 14 to 49 years, were treated with oral itraconazole (200 mg twice daily) for a mean of 3.9 months (range, one to six months; three patients continue on therapy). Two patients received two courses. Three patients had underlying cystic fibrosis, and three had severe asthma; four of the six required continuous high-dose systemic prednisone (mean, 43 mg/day; confidence interval [CI], 23 to 63 mg/day) at the start of therapy. In those treated for two months or longer, the mean total serum IgE level fell from 2,462 U/ml (CI, 752 to 4,202 U/ml) to 502 U/ml (CI, 123 to 880 U/ml) during each course, and the mean daily steroid dosage was decreased to a mean of 24 mg/day (CI, 11 to 37 mg/day). All patients experienced improvement in pulmonary function during the trial, with mean FEV, increasing from 1.43 to 1.77L/sec and mean FVC from 2.3 to 2.9 L in those treated for two months or longer. The mean steady-state serum concentration of itraconazole was 5.1 micrograms/ml (range, 1.8 micrograms/ml to 7.3 micrograms/ml); the patient with the lowest concentrations had the least significant clinical response. Cultures of sputum from two of three patients became negative for A fumigatus during therapy. No adverse clinical effects occurred except loss of libido in one patient. We conclude that oral itraconazole may be an effective adjunctive therapy in ABPA, possibly by clearing the airway of Aspergillus, and that randomized trials of this agent are warranted to better define its usefulness in this disorder.