Several perovskite-type oxides (ABO3) doped on their A and B sites show mixed (electronic and ionic) conductivity. Such mixed-conducting oxides are promising materials for oxygen- and hydrogen-permeating membranes that operate non-galvanically, i.e., without electrodes or external electrical circuitry. We are developing dense mixed-conducting ceramic membranes for selectively transporting oxygen or hydrogen. Sr-Fe-Co oxide (SFC), with its high combined electronic and ionic conductivities, has been developed into membranes that selectively transport oxygen during partial oxidation of methane to synthesis gas (i.e., “syngas,” a mixture of CO and H2). We have evaluated extruded tubes of SFC for conversion of methane to syngas in a reactor operating at ?850°C. Methane conversion efficiencies were >90%, and some of the reactor tubes were operated for >1000 h. We are also developing dense ceramic membranes to nongalvanically separate hydrogen from product streams that are generated during coal gasification, methane reforming, and water-gas shift reactions. Hydrogen selectivity in these membranes is nearly 100% because they contain no interconnected porosity. The hydrogen flux through these membranes has been measured in the temperature range of 600-900°C. The highest flux, ?20 cm3(STP)/min-cm2, was measured for a 20-mm thick membrane at 900°C. Performance of these membranes is stable during exposure to gas streams containing CO, CO2, and H2S. In this talk, the development of oxygen and hydrogen transport membranes will be described in detail, and data regarding permeation flux and stability will be presented.