There have been some reports on the efficacy and tolerability of an oral itraconazole (ITCZ) solution as prophylaxis for fungal infection in patients with hematological malignancies. However, there are some cases where the bitter taste of oral ITCZ solution leads to an interruption of administration because the patient refuses to take this medicine. Therefore, we prospectively investigated the pharmacokinetics and promotion of treatment adherence in patients taking oral ITCZ solution mixed with a beverage. Compared with the responses of patients taking oral ITCZ solution with water, the taste of the agent was improved significantly when mixed with orange juice, although the plasma concentration of the agent did not differ between the two groups. Using this method, we can expect an improvement in treatment adherence and this method can easily be applied in clinical practice. This method is highly useful and should become common knowledge.