A single-chamber solid oxide fuel cell made of Ni/YSZ anodes, YSZ electrolytes and SDC-impregnated LSM cathodes was tested in methane-oxygen mixture at furnace temperature equal to 700 degrees C. Two Ag wires were arranged on the anode surface to in situ measure the changes of the local anode resistance (R-s) during testing. Oscillations of the R-s the cell voltage and the actual temperature of the cell were observed and attributed to Ni/NiO redox cycles. Steady-state tests of the cell showed the corresponding oscillation patterns mainly depended on methane-to-oxygen ratio (M= 1, 2). Higher current density (J) to a certain extent could suppress NiO reduction and promote Ni oxidation. Scanning electron micrographs confirmed that Ni/NiO redox cycles had occurred mainly near the anode surface. The obtained results imply that gradual reoxidation of the Ni-anodes accompanying the various oscillation behaviors plays an important role in the degradation of the SC-SOFCs, especially under oxidation conditions. (C) 2011 Elsevier Ltd. All rights reserved.