Cyclic polarization of TiN electrodes in 6 M KOH at room temperature revealed relatively large anodic and cathodic overpotentials for water decomposition that depend on the surface structure of the material. Polished TiN electrodes also underwent a slow reaction during anodic polarization above the reversible potential for O-2 evolution that involved the formation of a reaction product film. The film was uniform over the surface of the electrodes and contained hydrous potassium titanate. A corrosion product, similar in composition but less uniform in appearance, formed on TiN after 4 months under open-circuit conditions in the same solution. Results indicate that the film forms slowly by a dissolution/precipitation mechanism and that the dissolution step gives rise to an oxidation peak observed in the cyclic voltammogram during anodic polarization. Since the film forms above the reversible potential for O-2 evolution and since the overvoltage for O-2 evolution depends on surface structure, it is not yet clear whether the formation of the corrosion film will compete with electrolysis reactions during the charging of structurally tailored, high surface area, TiN electrodes that are under development for ultracapacitor applications.