Bentonites which are the commercial grades of montmorillonite minerals have been used in over hundred different fields of industry. Therefore the extensive properties of bentonites must be quantitatively determined according to the fields of,their use and the standardization procedures have to be given. In this study, technological characterization of sodium- and calcium-bentonites were carried out comparatively and the quantitative data were given. The results show that sodium-bentonite can be used in petroleum, medicine, pulp and paper, metallurgy, casting, ceramic, catalyst and rubber industries with full advantage relative to calcium-bentonite. Sodium-bentonite might not be suitable for food industry because of its high swelling capacity which might cause unnecessary precipitation during limpidness procedure of a liquid food. Furthermore, however small particle size, high plasticity and thixotropy properties of sodium-bentonite provides its uses in construction industry, it can not be used in Portland cement due to its high water impermeability compared to calcium-bentonite.