To improve the adhesion of a metal coating to Teflon (polytetrafluoroethylene, PTFE), the ion beam technique has been used. Adhesion enhancement was obtained by irradiation of the Cu/Teflon interface with heavy ions in the GeV energy range. XPS analysis gave evidence for the long-range transport of Cu atoms into the polymer. Heating the Cu/Teflon sample after ion irradiation led to even stronger bonding between Cu and Teflon.