The initial oxidation of the (110), (111) and (100) copper surfaces, by changing the oxygen pressure and temperature, has been studied by low energy electron diffraction (LEED) techniques. The interactions of oxygen with copper showed different behaviors on each surface. The Cu (100) (2 × 3) -O and Cu (100) C (4 ×4) -O surface structures, which had not been observed, were obtained by heating in the low oxygen pressure range. Cu2O was formed on the (111) and (100) surfaces respectively and not observed on the (110) surface in the LEED pattern. The crystallographic relationships between Cu2O and the substrate are as follows ; (111) Cu2O // (111) Cu [110] Cu2O // [110] Cu (111) Cu2O // (100) Cu [110] Cu2O // [110] Cu (100) Cu2O // (100) Cu [110] Cu2O // [110] Cu The Cu (111) (2×2) R 30°-0 surface structure was observed on the Cu (111) surface. It may be considered that this structure appears in the transition process of the adsorption structure to Cu2O.