X-ray photoelectron spectroscopy was employed for the in situ study of the interactions between thermally evaporated copper atoms and neutral polyaniline (PANI) films of various intrinsic oxidation states ([= N-]/[-N-] ratios), as well as with the HClO4-protonated PANT film. Quantitative changes in the N Is core-level spectra, evolution of the Cu 2p core-level signals and the Cu LMM Auger line shapes, and angle-resolved changes in surface stoichiometry of these films with the progressive deposition of Cu atoms were carefully monitored. For the neutral films, the incoming Cu atoms appear to affect predominantly the nitrogen sites, resulting in a decrease in the intrinsic oxidation state of the polymer. Nevertheless, the effect was observed to be rather weak, possibly through a slight disruption of the pi-electron conjugation of the polymer backbone. However, for the protonated film, interactions with incoming copper atoms resulted in the decomposition of the perchlorate dopant and the formation of copper chloride species. Diffusion of Cu atoms into the bulk of the polymer was observed for all types of films studied. The interactions of the Cu atoms with the PANI surfaces were also compared with those of the Al atoms.