Adsorption coefficients for krypton and xenon on a number of commercial charcoals, including charcoals from the U.S., Japan, and the USSR, have been correlated with the specific surface areas and bulk densities of these charcoals. It was found that adsorption coefficients are not a linear function of the specific surface area, but instead reach a maximum at specific surface areas of 350 and 490 m2/g for the adsorption of krypton and xenon, respectively. Adsorbents with these low specific surface areas also have the advantages of lower cost, greater hardness, and greater resistance to ignition in comparison with highly activated carbons. No conclusive relationship could be established between bulk density and the adsorption coefficient for either krypton or xenon.