The formation of OH adsorption layers and the initial and later stages of the growth of anodic oxide have been studied on Cu(111) single crystal surfaces with STM. In 0.1 M NaOH Cu forms OH- adsorption layers for E > - 0.57 V (SHE) whereas oxide formation occurs at E > - 0.22 V. The adsorption of OH-and oxide formation can be followed by in situ electrochemical STM. At sufficiently high negative potentials even time resolved investigations become possible. OH adsorption goes along with a surface reconstruction. Oxide formation starts with small non-crystalline grains and with oxide crystals in a later stage. In borax buffer pH 9.2 no stable image is obtained during the growth of the Cu2O films with d > 1 nm whereas the images of the duplex layer formed at higher potentials are stable again. These details are discussed on the basis of previous results on the chemical composition of the passive layer in alkaline solutions and its semiconducting properties obtained from XPS, UPS, and electrochemical and photoelectrochemical investigations.