Prophylactic effect of itraconazole (ITCZ) in mycosis associated with hematological malignancy was studied. In a total of 12 patients of hematological malignancy admitted to Hokkaido University Hospital from April, 2001 to March, 2002, six patients received 100 mg per day of ITCZ and the other six received 200 mg per day of ITCZ. ITCZ was administrated from the starting of chemotherapy, and from the time point capable of oral administration in bone marrow transplantation patients. ITCZ administration was finished based on docter's judgement. As the results of this study, three cases with 100 mg per day of ITCZ had mycosis, but none with 200 mg per day of this drug had it. Mild itching associated with ITCZ was found only one case. In conclusion, we suggest that ITCZ is effective and safe drug in terms of prophylaxis of mycosis.