The electronic conductivity of yttria-doped ceria, (CeO2)(1-x)(YO1.5)(x) (x=0.1-0.4, 0.1 step), was obtained as a function of oxygen partial pressure at T=973, 1073, 1173, and 1273 K by a dc polarization method using a Hebb-Wagner's polarization (ion blocking) cell over an oxygen partial pressure [p(O-2)] range of 0.1 to 10(-10) MPa. All obtained data were fitted as a sum of the electron conductivity having a p(O-2)(-1/4) dependence in the lower p(O-2) region and the hole conductivity having a p(O-2)(1/4) dependence in the higher p(O-2) region. The activation energy for the electron and the hole conductivity exhibits the yttrium concentration dependence in an opposite way, and the sum of two activation energies has been found to be independent of the yttrium concentration. The thermodynamic considerations were made to estimate the concentrations of electron and hole, leading to the tendency that the migration enthalpy for electrons and holes is independent of the yttrium concentration, although their concentrations exhibit a strong dependence. (C) 2008 The Electrochemical Society. [DOI: 10.1149/1.2990729] All rights reserved.