With compromised bone marrow function, patients with aplastic anemia (AA) and/and hypoplastic myelodysplastic syndrome (hMDS) are at an increased risk of invasive fungal infection. Moreover, the use of antithyocyte globulin (ATG), a part of standard first line treatment for AA/hMDS, increases the risk of fungal infection due to its antilymophocytic effects. It has been reported that fungal infection occurs most often in the first few weeks after initiation of ATG treatment, and the reported incidence of fungal infection overall varies from 9~80% for AA/hMDS patients. Among them invasive fungal infection accounts for 6-20% depending on reports. Such being the case, antifungal prophylaxis is recommended for AA/hMDS patients undergoing ATG treatment. More specifically, the British Committee for Standards in Haematology (BCSH) recognized the threat of increased invasive fungal infections in AA patients, and stipulated the use of mould (aspergillus) active azole, "preferably itraconazole or posaconazole" as prophylaxis. Unfortunately however, though many centers have adopted their own practice schemes, and antifungals have been routinely administered in the context of investigational regimens, there is no consensus as to which antifungal agent should be used.