Rutherford backscattering spectrometry (RBS), routinely used for the analysis of inorganic materials, is finding applications in the characterization of organic polymeric films, which may be sensitive to damage. To investigate ion beam effects on polyimide, pyromellitic dianhydride–oxydianiline films were exposed to He2+ ions in the energy range of 1.9 to 3.6 MeV, fluences of 0.25 to 3.0×1015 ions/cm2, and sample temperatures of 298 and 130 K. RBS, x-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, optical interferometry, and enhanced image analysis techniques were used to determine film changes during irradiation. RBS spectra collected in the range of specified fluences are essentially superimposable, except for differences in their signal-to-noise ratios. The damage is optically observed as a darkening of the film. At 130 K, there was no motion of the gold marker in the film, indicating no loss of mass. During irradiation, molecular rearrangements are detected and include cleavage of imide rings.