Abstract: This study was focused on the treatment of sites polluted with gasoline through the use of betonies clays. In this research, permeability tests were carried out on both natural and modified (organophilic) bentonites using gasoline (as an organic solution) and water (a base liquid). Moreover, X-rd analysis was performed on the clays to assess the adsorption of hydrocarbons by the soils. Regarding modified clay samples, results of permeability tests showed that the average permeability of the soils decreased from 7.2x10-4 to 6.2x10-6 cm sec-1 as a result of organics adsorption. For natural bentonite samples however, the average permeabilities were increased from 5.45x10-9 to 3.4x10-4 cm sec-1, as a result of hydrophilic characteristics of the soil. Regarding X-rd analysis, the results showed that the basal spacing (clay particles thickness) of the modified bentonites samples were increased from 27.07’ to 39.11’ due to the adsorption of gasoline hydrocarbons to the soil. These results demonstrated the efficiency of modified clays as effective barriers for treatment of gasoline contaminated soils.