Electrochemical data collected for the porous La1-xSrxMnO3+delta (LSM) cathode-yttria-stabilized zirconia electrolyte system were analyzed using a mathematical model capable of simulating both the steady-state and impedance responses. The model considered the distributed nature of the porous electrode and a parallel pathway for oxygen transport including gas transport and surface diffusion. Data were collected in low oxygen partial pressures ranging between 10(-4) and 10(-3) atm, where LSM was considered to be stoichiometric with respect to oxygen. Thermodynamically consistent kinetic and transport parameters were regressed from the steady-state polarization data. Three different parameter sets fit the general trend of the experimental data. The surface diffusion and adsorption/desorption parameters were cross-correlated, which underlines the difficulty in finding a unique set of fitting parameters. The parameter set with four adjustable parameters resulted in a high surface diffusion coefficient but slower adsorption/desorption kinetics compared to the other two parameter sets for which a lower surface diffusion coefficient was fixed. The predicted overall impedance at zero-dc bias conditions for three parameter sets had varying degrees of agreement with the data. Low and high frequency arcs attributed to adsorption and an oxygen transport process were observed in the faradaic impedance response. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3432410] All rights reserved.