Abstract: The adsorption of sodium decyl-,dodecyl-and tetradecyl sulfate on negatively charged TiO₂ surface has been investigated.The adsorption isotherms display a sigmoid pattern,indicating the lateral interaction between the adsorbed surface active ions The adsorption free energy and lateral interaction parameter were calculated based on the FFGequation from the adsorption and electrokinetic data.From the experimental results it was deduced that,the adsorbed surface active ions were laying flat and formed hemimicelles at the TiO₂/solution interface.