Electrocatalytic oxidation of methane over anodes in single-chamber solid oxide fuel cells, 0-10 wt % Pd-30 wt % Ce0.8Sm0.2O1.9 (samaria-doped ceria, SDC)-Ni\SDC\Sm0.5Sr0.5CoO3, was studied in a mixture of methane and air between 450 and 550degreesC. The addition of a small amount of Pd (0.145 mg cm(-2)) to the anode significantly promoted the partial oxidation of methane by oxygen to form hydrogen and carbon monoxide, which resulted in electromotive forces of ca. 900 mV from the cell and extremely small electrode-reaction resistances of the anode. The peak power densities, when using a 0.15 mm thick SDC electrolyte, reached 644, 467, and 269 mW cm(-2) at 550, 500, and 450degreesC, respectively.