CF4 and O-2 glow discharge treatment of biaxially oriented polypropylene film results in the surface incorporation of fluorine and oxygen atoms, respectively, together with an increase in surface roughness. The stability and extent of substrate modification have been investigated by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). The observed differences in physicochemical behavior can be accounted for in terms of extended Huckel molecular orbital theory.