This paper reports on synthesis and evaluation of an intergrowth oxide, GdSrCoO4+delta (GSCO), as a new cathode material for intermediate-temperature solid oxide fuel cells. The oxygen content and the thermal expansion coefficient of GSCO oxide powders were measured. The GSCO oxide shows a semi-conducting behaviour in air with conductivities increasing from 16 S cm(-1) at 500 degrees C to 65 S cm(-1) at 800 degrees C. The catalytic activities of GSCO oxides for oxygen reduction reactions are evaluated using symmetrical impregnated GdSrCoO4+delta-La0.9Sr0.1Ga0.8Mg0.2O3 (GSCO-LSGM) cathode fuel cells. The polarization resistances for such composites increase from 0.072 Omega cm(2) at 650 degrees C to 0.55 Omega cm(2) at 550 degrees C. Furthermore, thin LSGM electrolyte supported fuel cells with impregnated Ni anodes and GSCO cathodes exibit high power densities at reduced temperatures, e.g., 782 mW cm(-2) at 550 degrees C and 1314 mW cm(-2) at 650 degrees C, respectively. These results demonstrate that GSCO is a promising cathode candidate for intermediate-temperature solid oxide fuel cells with LSGM electrolytes. (C) 2014 Elsevier Ltd. All rights reserved.