Impure zirconia stabilized by 12 wt% yttria concentrate (85 wt% Y2O3+15 wt% rare-earth (RE)) was found to have high grain and grain-boundary electrical conductivities. The influence of the RE on the segregation of impurities was studied for four different compositions. Microstructure features are evidence for the enhanced segregation of impurities due to RE ions. The increased grain and grain-boundary conductivities are a consequence of the segregation of impurities.