Chronic granulomatous disease (CGD) represents an innate immunodeficiency: the reduced production of oxygen radicals in phagocytosing cells results in decreased ability to kill pathogenic microorganisms. The patients concerned suffer from severe recurrent infections due to bacteria and fungi. Prophylactic administration of trimethoprim-sulfamethoxazole, as usual in CGD-patients, has markedly reduced the incidence of bacterial infections. Now as before, however, there is a high risk to become affected by invasive fungal infections, mainly due to Aspergillus spp. which often are lethal. Therefore, a well-compatible antimycotic long-term prophylaxis effective against Aspergillus would be attractive. In the present study the compatibility of the oral triazole itraconazole was tested in 8 CGD-patients with high risk of Aspergillus infections. Itraconazole was administered in capsules with a dosage of 5.1 mg/kg body weight per day on an average for a mean range of 23 months. Periodically liver enzymes, renal retention and electrolytes were assessed as well as itraconazole serum levels. Aspergillus serology tests included complement fixation tests, IgG-ELISA, precipitation tests, IgE determination and Aspergillus-RAST. During the prophylactic treatment in all of the 8 patients no gastrointestinal side effects or hypersensitivity reactions were observed. Renal retention and serum electrolytes as well as liver enzyme values were in normal ranges with all patients. Itraconazole serum levels showed a marked intra- and interindividual variability. However, 82% of the peak levels were in ranges regarded as therapeutically effective for itraconazole. Under prophylaxis a clear decrease of Aspergillus IgG-ELISA values was observed in 5 of 7 patients.(ABSTRACT TRUNCATED AT 250 WORDS)