Abstract The electronic structure of a series of 3d transition metal oxides is investigated by core-level and valence band photoemission spectroscopy. The results are analyzed in terms of metal–ligand interactions and on-site correlation energies, using a simple cluster model approach. For some oxides we also present a comparison with band structure calculations. It is shown that the electronic structure of the early transition metal compounds is mainly determined by the strong hybridization between transition metal 3d states and oxygen 2p states, whereas correlation effects become more important for the late transition metals. Further evidence for a strong metal–ligand hybridization is supplied by LVV-Auger spectra of the nominal d0 compounds TiO2, V2O5 and PbCrO4, indicating a non-zero 3d occupation, in accordance with the cluster model results. We discuss briefly also the systematics in the exchange splitting of 3s spectra as function of the 3d occupation number.