Equilibrium studies were carried out for the sorption of Cr(VI)onto Kraft lignin as an adsorbent. The experimental data were fitted to the Freundlich, Langmuir, Temkin, Dubinin-Radushkevich, Redlich-Peterson, Sips and Toth isotherms by non-linear method. We presented the comparison of two- and three-parameter isotherm. Only non-linear regression method was used in selecting the optimum isotherm for the experimental data. The coefficient of correlation was used to select the best theoretical isotherm. The best two-parameter isotherm is equally Langmuir and Dubinin-Radushkevich isotherm. From three-parameter isotherms Redlich-Peterson isotherm proved to be the best. Generally. Redlich-Peterson isotherm was found to be the best representative for Cr(VI) adsorption on the sorbent. (C) 2011 Elsevier B.V. All rights reserved.