The properties of selected metal (Pt, Ni, Au)/YSZ single crystal interfaces have been investigated by current-voltage measurements and impedance spectroscopy. A three-electrode cell consisting of a quasi-point-contact metal working electrode and Pt reference and counter electrodes were constructed and studied under various conditions. The impedance response consists of at least two processes, both belonging to interfacial properties: a high frequency process with peak frequency between 10(4) and 10(3) Hz, and a low frequency process with peak frequency between 0.5 and 50 Hz. An increase in overall electrochemical reaction rate and in the interfacial capacitance under prolonged anodic polarization was observed. A mechanism based on the spillover of oxide or hydroxide ions on the metal surface is proposed.