Modification of the double perovskite Sr 2 MgMoO 6−δ by La substitution has shown that Sr 2−x La x MgMoO 6−δ with 0.6⩽x⩽0.8 has better performance as the anode of a solid oxide fuel cell. With a Sr 1.2 La 0.8 MgMoO 6−δ anode, LSGM electrolyte, SrCo 0.8 Fe 0.2 O 3−δ cathode, and a La 0.5 Ce 0.4 O 1.7−δ buffer layer between the anode and the electrolyte, a maximum power density of 550mW/cm 2 has been obtained for a SOFC operating on wet methane (3%H 2 O) at 800°C. The performance of the SOFC using C 2 H 6 fuel, like that of CH 4 , changes little on switching from dry C 2 H 6 to 3% H 2 O/C 2 H 6 , but improvement with wet C 3 H 8 shows that some steam will need to be added to a moderately desulfurized natural-gas fuel.