Removal and fixation of As (III) and As (V) from aqueous solution by soil/bentonite mixtures were studied to develop reliable clay liners for waste landfill sites. One of two soils such as, Masatsuchi. soil (weathered granite) and Murram soil (pumice) was used as a main body of the liner, and Wyoming bentonites were mixed with the soils because of its superior impermeability. As the result of batch experiments, it was shown that large part of As was removed by Masatsuchi soil without pH buffer, andth e result was better than those of Murram soil. Both soils appeared to have best adsorption of As (V) and As (III) within pH ranges of 3-6.5 and 7-9.5 at where the dominant species in the aqueous solution were H2AsO4- and H2AsO3-, respectively. A long-term leak test showed that Masatsuchi soil-Wyoming bentonite combination had the ability to remove all the As (III) from 4 ppm aqueous solution for more than 100 days.