An intermediate-temperature solid electrolyte fuel cell has been developed that employs a proton-conducting solid electrolyte and uses ammonia directly as the hydrogen-containing fuel. Preliminary tests demonstrate that Gd-doped barium cerate is a suitable electrolyte material for a direct ammonia fuel cell operating at intermediate temperatures. When ammonia was fed directly at 700degreesC, a 2 cm(2) x 1.3 mm pressed electrolyte wafer with a supported platinum anode catalyst produced 50 mW power at 100 mA current. Fuel cell performance using ammonia was only marginally lower compared to pure hydrogen, and this was attributed to production of nitrogen during the ammonia cracking which dilutes the hydrogen fuel. Complete conversion of ammonia to hydrogen is possible due to the fuel cell's ability to continuously remove hydrogen from the anode chamber, as well as supply the necessary heat for the ammonia cracking reaction. Nitrogen and water are the only chemical products of the direct ammonia fuel cell utilizing a proton-conducting solid electrolyte. (C) 2004 The Electrochemical Society.