The in-vitro activity of amphotericin B, itraconazole and voriconazole against 130 clinical and 20 environmental Aspergillus fumigatus isolates was tested with an agar dilution method using RPMI 1640 medium. Itraconazole-susceptible (AF71) and -resistant (AF90) isolates were included in each test and all isolates were tested in duplicate. Geometric mean MIC values (ranges) at 48 h and 72 h were, respectively, amphotericin B, 0.91 (0.25-2) and 1.50 (1-4) mg/L; itraconazole, 0.25 (0.06-1) and 0.48 (0.125-8) mg/L; and voriconazole, 0.56 (0.25-8) and 0.78 (0.25-8) mg/L. The reproducibility of the results was high for all drugs. In-vitro resistance of A. fumigatus to the tested antifungal agents was uncommon and the MICs of itraconazole were half those of voriconazole (P < 0.01).