The progress toward a commercial solid oxide fuel cell (SOFC) continues to be a slow struggle due to materials, stacking, and system challenges. One long-term challenge has been the search for suitable cathode materials for use on intermediate (650-800 degreesC) yttria-stabilized zirconia (YSZ) electrolytes and low-temperature (500-650 degreesC) gadolinia-doped ceria (CGO) electrolytes. The present study has identified La(Sr)FeO3 and possibly Pr(Sr)FeO3 as potential cathode materials for YSZ. A La-deficient La(Sr)FeO3 cathode has achieved an area-specific resistance of 0.1 Omega cm(2) at 800 degreesC, with stable long-term performance. On CGO, Pr(Sr)CoO3, Gd(Sr)CoO3, and Sr(Co/Fe)(1.5)O-3.25 have all achieved an area-specific resistance close to 0.1 Omega cm(2) at 650 degreesC, with relatively stable long-term performance, but further reduction in temperature to 600 degreesC is necessary for efficient CGO operation. (C) 2003 The Electrochemical Society.