Core-level Spectroscopy in Condensed Systems describes how recent improvement of various experimental methods, together with new light and x-ray sources, have provided fresh information about the electronic states and atomic structures of a wide variety of materials. The topics coveredrange from the high-energy spectroscopy of bulk electronic states of rare-earth and transition metals and compounds, including high T superconductors, to recent developments in photoelectron diffraction and other surface problems, all with emphasis on theoretical aspects.