This paper deals with the bipolar switching properties of Ni\NiO\Ni cells for which the NiO layer is made by thermal oxidation of Ni layers. Physical characterization of the NiO layer revealed a strong deficiency in oxygen and a defective crystal structure. This microstructure allowed reproducible bipolar switching, which we attributed to the drift of oxygen anionic species and redox reactions at the anode. Conductive atomic force microscopy (C-AFM) experiments on Ni\NiO surfaces showed the scaling potential of the bipolar switching. C-AFM and macroscopic electrical measurements showed similarities and consistent results related to oxygen movement effects at the nanometer scale through relaxation processes and switching events. A discussion is conducted on the origin of the change in resistance, observed either at a microscopic or at a macroscopic scale. A distinction is made between electrochemical redox reactions taking place along conductive channels near the Ni\NiO\Ni top electrode and local changes of oxygen-vacancy densities. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3454199] All rights reserved.