The spatially-resolved local impedance can be measured by 'Millicontact Impedance Spectroscopy (MIS)', which involves the use of an array of sub-millimeter-scale electrodes. In stabilized zirconia and gadolinia-doped ceria electrolytes with highly resistive grain-boundaries, MIS could measure the local impedance precisely and revealed the spatially-resolved changes in the grain-interior and grain-boundary resistivity. The validity of this technique was illustrated using the examples such as the design of a new scavenger material and an analysis of the diffusion of the siliceous phase along the grain boundary. (C) 2008 Elsevier B.V. All rights reserved.