Solid-oxide fuel cells (SOFCs) are an energy conversion device that theoretically has the capability of producing electrical energy for as long as the fuel and oxidant are supplied to the electrodes but performance is expected for, at least, 40,000 h. In reality, performance degradation is observed in planar SOFC with metallic bipolar plate under steady and repeated thermal cycling conditions, which limits the practical operating life of these SOFCs. In this paper, the advances in SOFC are briefly summarized and the aging mechanisms of some components (anode, cathode and interconnect) in SOFC are discussed. The emphasis is given to aging mechanisms due to instability of materials and microstructures under real operation conditions. Identification of aging kinetics contributes to improvement in the stability of SOFC. It is indicated that development of new materials, optimization of microstructures and lower operating temperatures are desirable for the long-term stability of SOFC. Beneficial operation condition of SOFC is also proposed. (C) 2003 Elsevier B.V. All rights reserved.