The performance and the long-term operating properties of solid oxide fuel cells (SOFCs) using BaCeO0.8GdO0.2O3-alpha (BCG) ceramics as the electrolyte have been investigated. A hydrogen-air fuel cell using BCG electrolyte with a thickness of 0.5 mm exhibited good performance at 800 degrees C. Its short-circuit current was 0.9 A cm(-2), and there was hardly any degradation of BCG electrolyte in 1600 h of operation. When a quasi-fuel gas containing 8% CO2, which was expected by the reformation of the city gas (CH4) at 800 degrees C, was supplied to this cell, its short-circuit current was 0.63 A cm(-2) and the cell worked stably under the discharge current density of 100 mA cm(-2) for 2500 h. Some sintered metals (Fe, Co, Ni) were examined as a anode material for this electrolyte. Ni is a promising anode material for BCG electrolyte from the point of view of performance and durability.