Hydrolysis of methyl alpha- and beta-D-glucopyranosides was performed in the presence of protonic-form zeolites such as a dealuminated Y-faujasite with a Si/Al ratio of 15, at temperatures ranging between 100 and 150 degrees C, and in water as the solvent. The beta/alpha ratio for the hydrolysis reaction rates was found to be equal to 5-6, whereas a;ratio of 2-3 was reported in the literature for the homogeneous reaction. The observed higher beta/alpha ratio is proposed to result from the reinforcement of stereoelectronic effects which were shown to apply in reactions taking place on the surface of a solid. Those effects operate in a classical manner on a molecular standpoint, but they are reinforced due to the favorable interaction of oxygen electron lone Fairs with the electron-deficient species present on the surface of the solid, protonic species in the case of zeolites.