An experimental study was made of the adsorption and desorption of linear alkylbenzenesulphonates (LAS) from a detergent mixture onto different preparations of potassium kaolinite at 25°C in 0.01 M KHCO 3 and pH between 7.6 and 7.8. Oxidation treatment of the clay to remove organic matter was found to affect the adsorption behaviour considerably. The isotherm for the clay preparation without any oxidation treatment was indicative of a cooperative adsorption mechanism. The HPLC analysis of the surfactant solution and LAS extracted from the solids after adsorption, indicated the preferential adsorption of the longer chain C12 and C13 homologues of LAS. The Henry's law adsorption constants (partition coefficient) were evaluated for each of the homologues for one of the clay preparations. The increase in the free-energy of adsorption for the addition of one CH 2 group to the alkyl chain was estimated as 3.17 ± 0.23 kJ mol −1. The adsorption of the LAS component at concentration < 5 mg dm −3, was found to be reversible and dominated by a hydrophobic interaction at the surface.