The partial protonic, oxide ion and electronic conductivities of lanthanum tungstate (La28-xW4+xO54+delta with x = 1, LWO54) and 30% molybdenum substituted lanthanum tungstate (Mo-LWO54) have been extracted using the EMF method. LWO54 is a relatively pure ionic conductor up to similar to 800 degrees C; above that temperature electrons start to contribute significantly (under reducing conditions). The maximum protonic conductivity is similar to 2-3 x 10(-3) S cm(-1), and protonic conductivity dominates the ionic regime under wet conditions below similar to 700 degrees C. Above this temperature, oxide ion conductivity dominates the ionic contribution. The protonic and oxide ion conductivities for Mo-substituted LWO54 are quite similar to the Mo-free material, while the electronic conductivity is almost one order of magnitude higher for the former in wet 5% H-2/Ar. From this report is clear that nominally undoped lanthanum tungstate is most suited for applications as electrolyte in proton conducting SOFCs, while Mo-LWO54 presents improved mixed proton-electron conductivity for use as dense membrane for hydrogen separation. (C) 2013 Elsevier B.V. All rights reserved.