Electrochemical behavior of the strontium doped lanthanum manganite (LSM) electrode under cathodic and anodic current treatment was investigated by a.c. impedance spectroscopy and cyclic voltammetry. The reversible behavior of the LSM electrode may be related to the partial reduction and oxidation of the Mn ions under cathodic and anodic polarization. The performance of the LSM electrode was found to depend on the oxygen vacancies at the LSM surface, which would promote the transport of oxygen intermediate species at LSM surface close to the three-phase boundary (TPB) region. Results show that the impedance resistance of LSM electrode reduces with the increase of cathodic DC bias. The exponential dependence of Q(H) and Q(L) on the cathodic overpotential suggests that the reaction processes associated with the high- and low-frequency arcs to be chemical or physical processes. (C) 2003 Elsevier B.V. All rights reserved.