Supported Ruthenium: Silver bimetallic alloy system dispersed on a high surface area Alumina support prepared by co-impregnation method was studied using CO-chemisorption for the determination cb active metal site/metal surface area. The data indicates the presence of Ag on the surface of Rn. With me increase of Ag loadings a decrease in the CO adsorption occurred indicating that presence of Ag masks the active sites responsible for M-adsorption. The data has been interpreted in teems of geometric and electronic effect caused by the addition of Ag.