Oxygen plasma treatment of ABS polymer surfaces has the effect of increasing the adhesion of evaporated metal films on those surfaces. To help understand this, surfaces of commercial ABS and polypropylene were examined with ESCA both before and after oxygen plasma treatment. The plasma treatment was found to change the basic chemical nature of the polymer surface by increasing the number of single and double bonds between carbon and oxygen atoms. It is suspected that these additional carbon–oxygen chemical bonds affect the adhesion between polymers and metals. In addition to the carbon–oxygen bond formation, the plasma treatment removed residual impurities of silicon and increased the residual amounts of other metallic impurities originating in the bulk. The binding energies of these metallic impurities are all indicative of oxides.