The cathodic polarization behavior of strontium-doped lanthanum manganite (LSM) fired on stabilized zirconia electrolyte was investigated. The performance of LSM was enhanced significantly during discharge operation. The subsequent relaxation behavior under open-circuit state proceeded with two steps. A comparative study was also performed on strontium-doped lanthanum cobaltite (LSC) electrodes. The cathode potential of LSC with stabilized zirconia electrolyte decreased significantly at first and then increased gradually under current-static cathodic polarization. The subsequent relaxation in the open-circuit state also proceeded by two steps. When the interlayer of Sm-doped ceria (SDC) was introduced between electrolyte and cathode, the performance enhancement under cathodic polarization became much smaller regardless of the cathode materials, LSM and LSC. The mechanisms for the polarization behavior of LSM and LSC were discussed based on the obtained results. (C) 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.