Medical grade UHMWPE-s: GUR 1020 and 1050, were subjected to ion bombardment with H 2+, He+, Ar+ or Ag+ of different energy and various doses. The work presents changes to micromechanical profiles and surface morphology (AFM, SEM) of polyethylenes due to the treatment. Mechanisms behind the modification have been proposed owing to structural and chemical analyses by s-SIMS, FTIR-IRS, confocal Raman microscopy and “nuclear depth profiling”. Studies revealed that hardness of the surface layer increases due to radiolysis, probably leading to cross-polymerization of polyethylene. The depth of modification is limited to the penetration of ion beam, being dependent on a dose and a kind of ions applied. The treatment results additionally in oxidation, which together with a development of the surface geometry is responsible for its hydrofilization and, in some cases bacteriostatic character. Friction and wear of polyethylenes under a high load, adequate to extreme conditions of exploitation of hip joints, can be reduced even by three times, due to a proper ion beam treatment.