Plasma-based ion implantation was used to modify the surface of ultra-high molecular weight polyethylene. High-purity N-2, He and H-2 gases were ionized in radio frequency (rf) discharge and implanted at acceleration voltages of 20-30 kV with dose of 2 X 10(17) ion/cm(2). The first-order Raman spectra with probe wavelengths of 785 nm and 488 nm as well as infrared reflection spectra were recorded. It was established that considerable dehydrogenization took place at these treatments and incorporation of oxygen was also detected. Amorphous carbon layer was formed after H+ and N+ treatments. The He+ implantation caused formation of a region with highly graphitic character. (c) 2004 Elsevier B.V All rights reserved.