We developed a new in vitro method of evaluating antifungal molecules. Fungal growth was determined by measuring glucose consumption, the only carbon source in a synthetic medium. First, the growth of 12 Aspergillus fumigatus strains was studied. Glucose consumption was an excellent indicator of fungal growth. Second, the partial inhibition of growth was calculated in terms of the 90% or 50% inhibitory concentration for the 12 strains after treatment with itraconazole and amphotericin B. With a 3-day incubation time, the calculated 90% and 50% inhibitory concentrations agreed with those obtained by a macromethod and with those reported in previous publications. In each case the high degrees of efficacy of itraconazole and amphotericin B against A. fumigatus were confirmed. Partial inhibition induced by low concentrations of antifungal agents was quantifiable by this new method.