Aluminum is a very important element because of its many practical applications, and XPS provides an attractive method for the investigation of, and distinguishing between, aluminum and its compounds. The Al2pcore XPS spectra shows a substantial shift (about 2 eV) between the metal peak and compound peaks, and the metal peak width is much less than the width of the compound peaks. This fact has been used in numerous studies where the Al2pspectrum can be easily curve fitted to identify a percentage area due to the metal and due to aluminum compounds. Several measurements of this kind, representing aluminum metal and 11 of its compounds, have been collected in a special issue ofSurface Science Spectra. This Introduction summarizes the data to be presented and provides an overview of the use of and interpretation of XPS studies of aluminum and its compounds.