Measurements of the energy distributions of emitted electrons from Si, GaP, and ZnS allowed the determination of the relative positions of some core levels of these materials and the optical density of states of the valence band in Si. These energy levels were determined relative to the Fermi level. The electron emission was induced by monochromatic X-rays (AlKα). These results are compared with values obtained from OPW calculations for the valence bands and selfconsistent Hartree-Fock-Slater calculations for the core states.