The transference numbers for oxygen ion (to) in several LaGaO3-based materials are determined from oxygen concentration cells using the materials as the electrolyte, including La0.8Sr0.2Ga0.8Mg0.2O3-delta (LSGM8282), La0.8Sr0.2Ca0.5Mg0.15CO0.05O3-delta (LSGMC5) and La0.8Sr0.2Ga0.8Mg0.115CO0.085O3-delta (LSGMC8.5). Analysis indicates that the accuracy in determination of oxygen ion transference number depends on the electrode polarization resistances of the concentration cell as well as the transport properties of the materials studied. For example, the ratio of open cell voltage to Nernst potential is a good approximation to the ionic transference number for LSGM8282. However, this approximation is no longer adequate for LSGMC5 and LSGMC8.5; the effect of electrode polarization resistances must be taken into consideration in estimation of the ionic transference numbers. In particular, the ionic transference number for LSGMC5 is as high as 0.99, suggesting that it is a promising electrolyte material for low-temperature solid-state electrochemical applications. (C) 2008 Elsevier B.V. All rights reserved