In order to verify an effectiveness of a dielectric relaxation in the investigation of oxygen ionic conduction mechanism, dielectric and DC, AC measurements have been carried out for single crystalline 8 mol% YSZ. Total activation energies in the dielectric relaxation and the electrical conduction was almost same below T-c. Activation energies change at T-c. Disagreement of both energies above T-c have been improved by the modification of the dielectric relaxation analysis. (c) 2005 Springer Science + Business Media, Inc.