A variety of isothermal electrochemical applications of mixed ionic electronic conductors are due to their variety of isothermal mass and charge transport properties. For applications of a mixed conductor or for material selection for a specific application, it is, thus, necessary to document all these properties on each mixed conductor material, and they used to be measured by one method or another. We hereby propose to represent all these isothermal properties compactly and succinctly in terms of Onsager transport-coefficient matrix. We present, together with their working principle, the simple experiments to completely determine the Onsager matrix, and report the as-determined matrices for the systems of e.g., Ti0.99Ga0.01O2- delta, Ce0.8Pr0.2O2-delta and La2NiO4+delta. (C) 2012 Elsevier B.V. All rights reserved.