Full text can be accessed at http://www.sciencedirect.com/science/article/pii/S0169131703002588Hydraulic conductivity of compacted specimens consisting of 1 of 16 clay samples and siliceous sand/natural soils was measured using permeameters with flexible wall cells. Clay samples studied were eight natural bentonites, one purified montmorillonite, five standard clay samples, one synthetic hectorite, and two cation-exchanged bentonites. The clay content to whole solid was fixed at 11.5% w/w, and the mixtures were rammed in a mold to form disk compactions. A higher hydraulic conductivity was observed with increase in the Ca/Na ratio of clay. Hydraulic conductivity was also affected by bentonite content of the clays and the mineral content. A relation between the hydraulic conductivity and the characteristic index properties of the clays such as chemical concentration, methylene blue adsorption capacity (MB), and so on were elucidated, and then a polynomial expression was derived to reproduce measured hydraulic conductivity data. This relation was then utilized to estimate hydraulic conductivity of blended bentonites from characteristic properties of the component bentonites.