Abstract One- and two-electron excitations of core electrons into unoccupied states of the correlated 3d transition metal monoxide MnO(100) were investigated by core electron energy loss spectroscopy (CEELS) and appearance potential spectroscopy (APS: SXAPS and TCAPS) at the metal 2p and the ligand 1s thresholds. Unlike in the spectra of NiO, the number of the structures in the APS spectra at the oxygen 1s threshold exhibits no direct influence of the electron correlation, because all dominant peaks can be explained by one-electron transitions of an oxygen core electron into unoccupied manganese 3d, 4s and 4p states. Integrated CEELS spectra and APS spectra at the oxygen 1s threshold show good agreement. But in the APS spectra at the manganese 2p threshold we find two-electron excitations which are absent in one-electron excitation spectra. In this case a value for the electron correlation energy Udd can be estimated.