The adsorption of polyoxyethylene mono soya bean fatty acid [Soy (EO)20,40and80] and polyoxyethylene (80) monolinoleate [Li(EO)80] onto Na-montmorillonite has been determined at 30°C. The adsorption isotherms of all the tested surfactants exhibit an L-shaped following the Langmuirian model. The experimental adsorption data are fitted to Langmuir adsorption equation, the maximum amount adsorbed, Γmax, and the minimum area occupied per molecule, Amaxat the pseudo-plateau have been calculated. Γmaxvalue increases with the increase in the number of ethylene oxide units following the order, Soy (EO)20< Soy (EO)40Soy (EO) ≃ Li (EO)80. Both Soy (EO)80and Li (EO)80nearly show the same adsorption behavior.