The oxygen nonstoichiometry, the total conductivity, and the electronic conductivity of [(ZrO2)(0.8)(CeO2)(0.2)](0.9)CaO)(0.1) were measured by using high temperature gravimetry, de four-terminal method, and Hebb-Wagner＇s dc polarization technique, respectively. The change in the oxygen nonstoichiometry was explained by assuming Ce＇(Zr,) Ca"(Ze) and V-o(..) as major defects. At 1173 K and p(o2) = 1 similar to 10(-11) atm, the total conductivity corresponded to the ionic conductivity is proportional to [V-o(..)] At the lower p(o2), although the oxygen vacancy increased with the decreasing p(o2), the ionic conductivity decreased. The relation between [V-o(..)] and the ionic conductivity was similar to that in stabilized ZrO2 with various CaO contents. It was shown that the electronic conductivity is proportional to [Ce＇(Zr)], which is not in accordance with the hopping-type conduction between Ce3+ and Ce4+. Assuming all Ce＇(Zr) release conduction electrons, the calculated mobility is in the order of 10(-6) cm(2) V-1 s(-1) at 1173 K and does not correspond to the band conduction model. It was considered that most of the electrons are trapped at the donor level formed by Ce＇(Zr) and only a small portion of the electrons is excited to conduction band as carriers.