The effect of the aeration rate on pullulan production from beet molasses by Aureobasidium pullulans P56 in a stirred tank fermenter was investigated. A maximum polysaccharide concentration (23 g/l), biomass dry weight (22.5 g/l), polysaccharide yield (40%) and sugar utilization (96%) was achieved at an aeration rate of 1.0 vvm. A. pullulans grown on molasses produced a mixture of polysaccharides. The highest value of pullulan proportion (35% of total polysaccharide) was obtained at the highest aeration condition (1.0 vvm). Apparent Viscosity of the extracellular polysaccharide increased with the increase of polysaccharide concentration and the pH, but it decreased with temperature. The highest value of viscosity was achieved at pH 8.0 and temperature 20 degrees C when the polysaccharide was produced by A. Pullulans with aeration rate of 1.0 vvm.