Adsorption of endosulphan on uncontaminated sandy loam and silt clay loam soils in acetone-water and methanol-water mixtures at different f(s) values has been studied by the batch technique. Higher adsorption of endosulphan was observed on sandy loam soil than on silt clay loam soil, as was predicted from Freundlich constant K values and partition coefficient KD values. The K and K-D values also confirm that adsorption of endosulphan was higher in acetone-water mixtures than in methanol-water mixtures and decreases with increases in the volume fraction of solvents (acetone, methanol), the f(s) values. The data were used to evaluate the cosolvent theory for describing adsorption of endosulphan in acetone-water and methanol-water mixtures, The aqueous phase partition coefficient K-DW (mol/g) normalized on f(oc) (fraction of soil organic carbon) for endosulphan was evaluated by extrapolating to f(s) = 0,