The operation of fuel cells based on proton conducting BaCeO3 solid electrolyte doubly doped with gadolinium and praseodymium is reported. Fuel cells were operated for up to 96 h with both hydrogen and ammonia individually as fuel. Results show that the performance of the cell is the same irrespective of the fuel used. The only chemical by-products of the ammonia fuel cell are nitrogen and water. The data shows that a fuel cell incorporating a doubly doped proton conducting electrolyte operated on ammonia fuel is a viable alternative to fuel cells utilizing hydrocarbon fuels as sources of hydrogen. Crown Copyright (C) 2004 Published by Elsevier B.V. All rights reserved.