The electrical, structural and electrochemical properties of a dense In2O3 layer in contact with a single crystal YSZ electrolyte were studied. As a result of de and ac investigations, it was found that under anodic polarization the rate of Faraday reaction at the surface of the In2O3 electrode is as low as in an ionically blocked electrode. Under cathodic polarization, however, the electrochemical activity of the electrode improves depending on the magnitude of the polarization voltage. Likewise, the electrode polarization resistance decreases after platinum or praseodymium oxide having been deposited on the surface of the In2O3 layer. The possible mechanism responsible for such a peculiar behaviour and the limiting step of the electrode reactions are discussed.