The numerous applications in various fields of chemistry and physics have clearly demonstrated the potential of X-ray photoelectron spectroscopy. A number of interesting experimental projects will be completed in the near future and papers with new and more reliable reference data will appear in the literature. Further refinement of the theoretical models will add to the fundamental understanding of the obtained results. And last, but not least new developments in instrumentation will keep pace with the practical and theoretical experience and open up new areas, which so far could not be penetrated because of resolution, sensitivity or sample handling problems.