This protocol describes a prospective, randomized study examining the safety and efficacy of Itraconazole for preventing fungal infections in patients with Chronic Granulomatous Disease (CGD). CGD is a genetic disorder in which phagocytes are unable to produce oxygen radicals. As a result, affected patients are prone to recurrent, severe infections with bacterial and fungal organisms. Patients with CGD of 5 or more years of age without evidence of infection at the time of study entry will be eligible for enrollment. Patients will be randomized to receive itraconazole or placebo tablets daily, in a double blinded fashion. In addition to itraconazole, all patients will receive antimicrobial prophylaxis against bacterial infection, and may in addition receive gamma-interferon as prophylaxis against infection. Randomization of patients will be stratified among patients receiving or not receiving gamma interferon. The primary endpoint of the study will be the development of culture or histologically proved invasive fungal disease. Patients will be monitored every three months for evidence of drug toxicity, and surveillance cultures of nasopharynx and stool will be obtained. The anticipated accrual period will be approximately 36-48 months.