Auger Electron Spectroscopy (AES) and x-ray photoelectron spectroscopy (XPS) have many aspects in common. Therefore, tests of aspects for one spectroscopy, applicable to the other, should be validated for both. Digital databases of elemental spectra for both AES and XPS have thus been measured using an electron spectrometer that has been fully calibrated for its intensity and energy axes. These databases of true spectra give absolute Auger electron yields and relative photoelectron yields. The AES data are measured for both 5 and 10 keV electron beam energies, whereas the XPS data are measured for both Al and Mg unmonochromated x rays at the magic angle. In addition to these we have measured reflected electron energy loss spectroscopy (REELS) data to provide a third database. The combination of these databases allows a refinement of the theories to obtain an overall convergence between theory and experiment. Improvements to the theory have been obtained by identifying three classes of parameter, those (i) for both AES and XPS, such as electron transport, the methodology of evaluation of peak areas, and the spectrometer response function, (ii) for AES only, such as the electron ionization cross section, backscattering, and specific electron backgrounds, and (iii) for XPS only, such as the photon-ionization cross section. Additionally, the use of REELS data for background subtraction seems significantly better than the use of any one single Tougaard universal cross section in the determination of the AES and XPS intensities in the databases. The formalism for quantitative analysis in AES and XPS, using relative sensitivity factors, has been revised to develop an accurate matrix-less formalism that is very simple for use by the analyst. This formalism, involving "average matrix sensitivity factors" rather than "pure element sensitivity factors," has the same accuracy as the matrix formalism but its simplicity permits ready extension to systems beyond binary. [S0734-2101(00)08704-2].