During a chemotherapy induced leukopenic period fluconazole (3 mg/kg/day i.v.) was administered as empiric antifungal treatment in a 5-year-old girl with leukemia and a presumed catheter infection due to Staphylococcus epidermidis. Despite intensive treatment with antibiotics and fluconazole the patient died. In one blood culture Candida krusei was isolated post mortem, and at autopsy Aspergillus fumigatus was found in multiple organs. Both fungi showed high MIC values to fluconazole. We feel that this drug should not be used when the possibility of a systemic infection with an unidentified fungus exists.