The polarization resistance (R-p) of Ag/(ZrO2)(0.9)(Ln(2)O(3))(0.1) (Ln = lanthanides) oxygen electrodes was measured as a function of the resistivity (p) of the electrolyte, which was systematically changed by using different Ln dopants. It was found that R-p increases with p in contrast with the expectation from the usual electrode theory assuming the adsorption and diffusion of O-2 molecules on the electrode surface. We attempt to explain the p-dependence of R-p based on a non-uniform electrode model which assumes locally variable polarization resistances in combination with the interfacial electrolyte resistance. According to this model, as p is higher, the current distribution becomes spatially more uniform, therefore making the polarizations more non-uniform. The more non-uniform is the polarization, the larger is R-p, because it is determined by the largest local polarization. The model can thus explain why R-p increases with p, without assuming any dependence of the local polarization resistance (r(p)) on p. If this mechanism dominates R-p, a negative slope of t(o) (time constant of decay curve) versus R-p plots is expected while a positive slope from the conventional electrode theory. In fact, R-p decreases with to in a high p region, thus proving that R-p is controlled by the non-uniform polarization mechanism proposed. R-p versus p experiments were also carried out for Au/(ZrO2)(0.9)(Ln(2)O(3))(0.1) electrodes. It was found that R-p decreases with p in contradiction to the Ag electrodes. This p-dependence of R-p was explained in terms of the unusual decrease of the interfacial electrolyte resistance, which might be due to a highly concentrated current density near the 3 phase boundary. (C) 2004 Elsevier Ltd. All rights reserved.