The ruthenium Pyrochlores, A(2)Ru(2)O(7-delta) (A = Pb Bi), and ruthenium perovskites, (ARuO(3) (A = Ca, Sr) were characterized as new electrode materials fur solid oxide fuel cells. The electrical conductivity, cathodic polarization, thermal expansion, and reactivity with yttria-stabilized zirconia were examined. The pyrochlores showed low cathodic overpotential even at 800 degrees C, metallic behavior with high electrical conductivity, and no reaction with yttria-stabilized zirconia at 900 degrees C. The thermal expansion coefficient of the bismuth pyrochlore was comparable to yttria-stabilized (8 mol % Y2O3 content) zirconia. The pyrochlores are very attractive for application as cathode materials in a solid oxide fuel cell with low operating temperature.