X-ray emission oxygen Kα and 3d transition metal Lα spectra for MnO, FeO, CoO, NiO, and CuO have been compared in the same energy scale by using Me 2p and O 1s binding energies. In the valence band of CuO the so-called d-p resonance between Cu 3d and O 2p states was observed. The 3d metal Lα-spectra for these oxides reveal both 3dnL and 3dn-1 electron configurations. The 3d transition metal oxides have been proved to be insulators with a ligand-to-metal charge transfer. Maximum values of the charge transfer are for CuO and NiO.