Methane and other hydrocarbons such as propane and butane are ideal fuels for SOFCs operating in portable devices for domestic or leisure use [J. Power Sources 71 (1998) 268]. This paper addresses the fuel entry conditions necessary for such devices. A gas manifold system was connected to a micro-tubular zirconia cell 2 mm diameter with lanthanum strontium manganite cathode and nicke/zirconia/ceria anode. Wire current collectors were used to obtain electrochemical performance data via a potentiostat system. The reaction products from the anode were analysed by mass spectroscopy to elucidate the reaction mechanism, and temperature programmed oxidation allowed the carbon deposition to be evaluated [Proceedings of the 4th European Solid Oxide Fuel Cell Forum, Luzern, July 200 1, p. 15 1]. Carbon deposition was substantial near open circuit voltage, when little oxygen was flowing to the anode. Dilution with inert gas or with CO2 caused a significant change in the reaction mechanism. The conclusion was that diluted methane could be fed directly into the SOFC, and that particular compositions (e.g. biogas at 30% methane and 70% carbon dioxide) gave optimum performance with little carbon fouling.