The grain-boundary resistivity of CaO . 2SiO(2)-in-diffused 8 mol%-yttria-stabilized zirconia (8YSZ-CS) or SiO-in-diffused 8 mol%yttria-stabilized zirconia (8YSZ-S) was determined by local impedance spectroscopy using submillimeter-scale electrodes. During sintering, a liquid formed at the top of the 8YSZ penetrates or diffuses into the 8YSZ interior. For CaO . 2SiO2-in-diffused 8YSZ, the grain-boundary resistivity of the specimen surface was observed to be 150 times greater than that of the interior, and grain growth was enhanced near the surface region. In contrast, for SiO2-in-diffused 8YSZ, the near-top surface region did not show enhanced grain growth and its grain-boundary resistivity was only nine times higher than that of the specimen interior.