This volume outlines the physical and methodical concepts of X-ray photoelectron spectroscopy (XPS) specifically for surface studies using both inner and valence electron levels. It discusses the theory and practice of XPS qualitative and quantitative analysis of solid state surfaces and provides lists of extended experimental and theoretical data necessary for the determination of concentration and thin film thicknesses. In addition it covers the many problems concerning in-depth profiling, ion sputtering rate and damages of the structure of altered layers, as well as applications of angular dependence of the intensities and photoelectron diffraction for surface studies. Also provided are the applications of XPS for the investigations of catalysts, adsorption, electronic surface states, oxydation of semi-conductors and alloys, minerals, including lunar regolith and natural gold, glasses, radiation damage, surface diffusion, polymers, etc.