The implantation of 90 keV N+ ions into polyethyleneterephtalate (PET) to fluences of 1 X 10(14)-1 X 10(17) cm-2 was studied. The changes in electrical sheet conductivity and polarity of ion-exposed PET were observed and the structural changes were examined using IR spectroscopy. One degradation process is a chain fission according to the Norrish II reaction. The sheet conductivity due to conjugated double bonds was increased by ten orders of magnitude as a result of ion implantation. The surface polarity of the PET samples increases slightly with increasing ion fluence.