The use of electron beam-generated plasmas produced in Ar/SF6 mixtures to modify the surface of ultra-high molecular weight polyethylene substrates is discussed. Changes in the surface energy, chemistry, and morphology are presented as a function of plasma operating parameters, along with simple system diagnostics to obtain a better understanding of the plasma-polymer interaction. For all conditions, the hydrophobicity of the material was increased via the incorporation of fluorine, and for some conditions, the surface was found to remain stable over the course of 1 year. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 117: 3515-3523, 2010