Upgrading of bentonites in sodium or mixed forms through wet separation methods is considered because such low solid suspensions require filtration followed by drying. These wet separation methods turn into effective and compatible processes for high selling prices such as water and solvent based bentonites. In this study, Na-bentonites were subjected to a series of multistage hydrocyclone testing to evaluate the separation efficiencies related to the hydrocyclone parameters such as vortex and apex diameters and feed pressures. In each hydrocyclone test, the run of mine bentonite was split into different fractions of various qualities. The separation efficiencies and the corresponding products were examined and characterized based on some technological properties such as cation exchange capacity, viscosity, swelling ability along with particle sizes, and chemical and mineralogical analyses. It is shown that for clay minerals such as smectites and also bentonite minerals, cation exchange capacity is the best method for assaying the concentration products and for evaluating the metallurgical balance though other characteristic properties such as chemical analysis, swelling, gelling and viscosity could be used as complementary. (C) 2010 Elsevier B.V. All rights reserved.