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Electrical resistivity of the unplasticized poly(vinyl chloride) copolymer (UPVC) films irradiated with high-energy proton beams was studied with reference to a control sample, as a function of both ion energy and ion dose. Upon irradiation with beam energy ranging from 25 up to 37 MeV and at a beam fluence of 0.225×1010 ion cm-2, the room-temperature resistivity of the insulating films decreased by four orders of magnitude from its original value. Furthermore, using 25 MeV proton beams over a wide range of fluence (1011-1015 cm-2), the room-temperature resistivity of the films decreased by only three orders. Then, the dependence of the resistivity ρ(T) on the ion energy and fluence was also observed as the temperature T was progressively increased up to 373 K. The observed behaviour of ρ(T) agrees with the charge transport model, consistent with a hopping mechanism in the polymer. In addition, the changes in the ac electrical resistivity of the irradiated UPVC films have been measured within the temperature range (293-373 K) and at different frequencies (100 kHz-3 MHz).