The electrical conductivity of BaTh0.9Y0.1O3-alpha was about two and three times larger than those of BaTh0.9N0.1O3-alpha and BaCe0.9Y0.1O3-alpha, respectively, around 1000 K in dry air, and increased in proportion to P-O2(1/4.4) at 1276 K in a dry atmosphere, indicating p-type electronic conduction. The transference number of oxide ions increased slightly with decreasing temperature and the activation energy of oxide ionic conduction was 0.42 eV. The water vapor pressure dependence of the total electrical conductivity may suggest a protonic conduction mechanism in BaTh0.9Y0.1O3-alpha.