We conducted a prospective, open study of oral itraconazole therapy (5 and then 10 mg/kg per day) to assess tolerance and potential efficacy in preventing fungal infections in patients with chronic granulomatous disease. Thirty-two patients were enrolled in one center between 1985 and 1991. Tolerance was excellent in all cases. Poor compliance was suspected in three cases. Two patients were excluded from efficacy analysis because itraconazole was used as part of therapy for pulmonary aspergillosis. Of 30 patients, 3 developed a fungal (Aspergillus) lung infection, an incidence 3.4/100 patient-years versus 11.5 in a historical control group that did not receive any prophylaxis (p = 0.13) and 9.55 in a historical group of patients who received daily ketoconazole prophylaxis (p = 0.19). The percentage of patients infected with Aspergillus was significantly different: 10% in the itraconazole group versus 34.4% in the untreated group (p = 0.013). These results require further evaluation through a comparative randomized trial to assess the possible benefit of itraconazole prophylaxis in patients with chronic granulomatous disease.