Applying in-situ combination of angle-resolved photoemission and inverse photoemission spectroscopy on clean Ge(001)2 X 1 surfaces we determined the binding energies of occupied and unoccupied surface states associated with the surface dimer of the 2 X 1 reconstruction at the high symmetric points GAMMABAR, JBAR, J'BAR, 1/2JKBAR and KBAR of the surface Brillouin zone. Together with the experimentally determined valence band maximum the results will be compared on an absolute energy scale with recent surface band structure calculations.