Fungal infections are a major problem among patients with hematological malignancies. To evaluate the efficacy of itraconazole (200 mg twice daily) in the prophylaxis of fungal infections in neutropenic patients, we conducted a prospective trial. A total of 61 patients with acute leukemia (113 cytotoxic chemotherapy episodes) were enrolled in the study. One patient in the itraconazole group was excluded because itraconazole was not taken due to gastrointestinal hemorrhage. Because the duration of neutropenia (neutrophil count, <0.5 x 10(9)/l) did not reach 7 days, 3 (1 patient) and 13 (4 patients) cytotoxic chemotherapy episodes in the itraconazole and control groups, respectively, were excluded. After these exclusions, the study population consisted of 31 patients (54 cytotoxic chemotherapy episodes) who had taken itraconazole and 24 patients (43 cytotoxic chemotherapy episodes) who had not taken itraconazole. Prophylactic treatment was initiated on the first day of chemotherapy and was continued until the end of the neutropenic period (absolute neutrophil count, >1 x 10(9)/l) unless a systemic fungal infection was documented or suspected. Thirteen episodes (24%) in the itraconazole group and 7 episodes (16%) in the control group proceeded to intravenous amphotericin B (P > 0.05). Fungal infections occurred in 9 episodes (17%) in the itraconazole group and in 5 episodes (12%) in the control group (P > 0.05). Overall mortality was five deaths in the itraconazole group and two in the control group. These deaths were not due to clinically documented fungal infection. In our study, efficacy of itraconazole in the prophylaxis of fungal infections in neutropenic patients was not detected.