The adsorption of oxygen on clean germanium has been widely studied by observation of the structural properties with LEED or by an investigation of surface states with surface conductivity and field effect mobility measurements. However, the correlation of structure with electrical behavior of such surfaces is difficult to determine when these measurements are made separately. In this study vacuum cleaved germanium (111) surface were exposed to oxygen up to one monolayer coverage, and electrical and LEED measurements were simultaneously made in order to determine a possible correlation between surface states and surface structure. The results show two different effects of oxygen on the surface state distribution: One is a change correlated with the conversion of the surface superstructure originally present at the clean surface (2×1 or 8 structure) to a 1×1 structure; the conversion is caused by adsorption of a small fraction of a monolayer of oxygen. The other effect is a change due to adding of new levels and/or removal of existing levels by the oxygen atoms adsorbed at the surface.