Enzymatic hydrolysis of cellulose has been studied using a novel multifrequency ultrasonic reactor. The optimum experimental conditions resulted in the percent glucose yield of 41.4% after 5 h using Avicel microcrystalline cellulose and cellulase + cellobiase enzymes at 50 degrees C and pH 5.2. It was found that the effect of ultrasound is mainly physical in nature and increased mass transfer because of increased surface area resulting from cellulose fragmentation in the presence of ultrasound was responsible for the observed increase in the glucose yield. The best cellulose hydrolysis was observed at 611 kHz and 104 W. Up to 70% glucose yield was obtained with prolonged time (40-50 h). The effects of ultrasound and enzyme on the surface and structure of the cellulose were studied using Brunauer-Emmett-Teller (BET) and X-ray diffraction (XRD).