Although the efficacy and safety of voriconazole to treat invasive fungal infections have been demonstrated in prospective trials, its use for secondary prophylaxis to prevent reactivation of these infections remains unknown. Delaying the scheduled treatment of leukemia until complete resolution of fungal infection may have major implications for prognosis. We report 11 leukemic patients with previous aspergillus (n = 10) and candida ( n = 1) infection who received voriconazole 400 mg/day intravenously or orally for between 44 and 245 days. Nine patients were scheduled for allogeneic stem cell transplant, and two for consolidation therapy for acute leukemia. None of the patients had a relapse of fungal infection, and scheduled treatment was delayed only once. Voriconazole was well tolerated, except in one patient who had abnormal liver tests secondary to hepatic graft-versus-host disease, and one who had visual disturbances. This small but homogeneous series indicates that voriconazole may be useful to prevent fungal relapse during at-risk periods in leukemic patients. Prospective trials are warranted to confirm these encouraging results.