A planar solid oxide fuel cell (SOFC) was designed to be operated in gradual internal reforming conditions under pure dry methane. Stable operation was achieved for about 30 h. This result was obtained by deposition onto a Ni-yttria-stabilized zirconia cermet of a highly active and carbon-deposition-resistant catalyst layer consisting of Ir/CeO2. The performances of this layer were first evaluated in situ at open-circuit voltage, and then the principle of gradual internal reforming associated with electrocatalytic dissociation was demonstrated. The best cell performances with CH4/H2O=1/4 were 0.1 A cm(-2) at 0.55 V (about 55 mW cm(-2)) at 1173 K.