Adsorption isotherms and isosteric heat data are presented for various nonpolar gases on oxide, metal, salt and graphite adsorbents. All adsorption isotherms, except those on graphite, were found to cross the P0-axis at a definite angle before four monolayers are filled, when the adsorption temperature is below the triple point temperature of the adsorbate. Apparently, for all adsorbents but graphite, the electric field emanating from the surface and/or the structure of the surface still strongly affects the molecular interactions in the higher adsorbed layers as P0 is approached. p ]If the number of adsorbed layers is finite as P0 is reached, this value of P0 can not be used in the BET equation for surface area determination. In the case of krypton adsorption or oxides at 77.60°K curved BET plots can be straightened by using P0 = 4.40 mm mercury. Employing a cross sectional area of a krypton atom of 17.65 Å 2 very good agreement will be obtained with the nitrogen BET surface area.