[en] Different aspects of photoelectronic spectroscopy (PES) as applied to catalysis and adsorption studies are analyzed. The physical principles of PES and experimental procedure are described in brief. The results of applying the above method in studying metallic, alloy, deposited and zeolite catalysts (in particular, oxide films of Mo, Re, W, V, Ru and rare-earth elements) are presented. The method is shown to be suitable for studying the valent and physical states and surface concentrations of elements in catalysts, the nature of adsorptive complexes, and the mechanism of surface reactions