The incidence of systemic fungal infections has risen, as shown by increases in the numbers of immunosuppressed or immunocompromised patients. The consequences of these fungal infections are occasionally serious. However, the efficacy of antifungal prophylaxis in patients receiving corticosteroid treatment has not been well investigated, even though they are susceptible to severe fungal infections. Therefore, we retrospectively evaluated the prophylactic efficacy of an antifungal agent-oral itraconazole solution (ITCZ-OS)-for immunosuppressed patients receiving corticosteroids in a single institution. Of 39 patients, 18 received prophylaxis with ITCZ-OS at a dose of 200 mg/day, and 21 did not. As a result, no fungal infections developed in the prophylactic group, but 7 of the 21 patients (33%) in the non-prophylactic group suffered from fungal infections consisting of 3 non-invasive candidiases, 2 invasive candidiases, and 2 invasive pulmonary aspergilloses. Among the non-prophylactic group, aging and hypoalbuminemia were statistically significantly associated with incidence of invasive fungal infections. Of the four patients with invasive fungal infections, three had concomitant chronic illness such as diabetes. Toxicity among the prophylactic group was not statistically significantly different from that of the non-prophylactic group. In addition, none needed discontinuation of the drug. These results indicate the potential antifungal prophylactic effect of ITCZ-OS for a subset of patients treated with moderate or high doses of corticosteroids.