Nearly stoichiometric CeN film is synthesized on a Re(0001) substrate in an ultrahigh vacuum system involving highly active N atoms in the growth process, generated by thermal decomposition of NH3 by use of a hot tungsten filament. The electronic structure of the CeN film as prepared is equivalent to that of a single crystal observed by in situ Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS). AES and XPS investigations show that CeN film is directly oxidized to CeO2 after exposure to O-2 at room temperature. However, CeN changes into Ce2O3 after annealing in similar to 10(-6) mbar of O-2 atmosphere at elevated temperature.