Abstract. Thin oxide layers of high purity metals are suitable as redox electrodes in aqueous solutions. Concentrations of hydrogen peroxide could be analyzed potentiometrically. In dependence on the pH-value Nerstian behaviour was observed in the range of 0.1-30 g/I (H202) approximately. It is assumed that this electrochemical behaviour of the oxide layer is mainly influenced by electronic and ionic defects. Alloys of vanadium and titanium are included in the investigation. In order to clarify the mechanism in detail, electrochemical measurements (voltammetry, EIS) and surface analytical investigations (XRD, AES, XPS) have been carried out.