Expanded polytetrafluoroethylene (ePTFE) is a stable polymer and widely used as a prosthesis because of its chemical inertness. However, ePTFE as an artificial dura mater is often associated with postoperative leakage of the cerebrospinal fluid (CSF) due to its very low adhesiveness to fibrin glue and surrounding tissue. To overcome this shortcoming the authors examined the effects of ion beam irradiation to ePTFE surface. The surfaces of ePTFE were irradiated with 150keV--He+, Ne-, Ar+ and Kr+ ions with fluences of 1 x 10(14), 5 x 10(14) and 1 x 10(15) ions/cm2. L929 fibroblasts were cultured for 24 hours on ePTFE sheets that had both ion beam irradiated and un-irradiated regions. It was confirmed that fibroblasts still adhered to the ion beam irradiated area. This phenomenon was observed under different condition of ion beam irradiation. Adhesive strength of fibrin glue to ion beam irradiated ePTFE was evaluated by tensile strength and burst pressure test using ePTFE patch. Both tensile strength and burst pressure were remarkably enhanced by ion beam irradiation. SEM study indicated that fibrin glue infiltrated and anchored into the gaps induced by the ion beam irradiation. Thus ion beam irradiation improved biocompatibility of the surface of ePTFE.