[en] The changes of composition and structure of polyimide films due to high-energy irradiation and high-dose implantation were studied by surface characterization techniques and the electric resistance measurement. Polyimide (C₂₂H₁₀N₂O₅)_n film specimens were irradiated with 4 MeV Ni³⁺ ions for the fluences from 3.5x10¹² cm^-2 to 1.0x10¹⁶ cm^-2. After irradiation with the fluence of 1.0x10¹⁶ cm^-2, the ratios of N/C and O/C decreased from 0.089 and 0.244 to 0.018 and 0.086, respectively. The generation of amorphous carbon areas dispersed in the irradiated polyimide film was suggested by Raman spectroscopy and electric resistance measurement. Nano-sized metallic particles were produced in the films by 130 keV silver ion implantation. The diameter of the particles was about 5 nm for the specimen implanted with 1x10¹⁶ cm^-2 and it increased with the implantation dose. On the other hand, no particles were observed in the specimen implanted with tungsten ion. (author)