In this study, the reformate operation of anode supported solid oxide fuel cells (SOFC) is characterized by electrochemical impedance spectroscopy. The characterization is performed over a broad measuring range of temperature and H/C/O-ratios of the fuel. The kinetic parameters of the electrochemical oxidation of the fuel are obtained directly from impedance measurements performed on anode-supported cells for SOFC. This is done by a combined distribution of relaxation times and an equivalent circuit impedance analysis method, which allows a highly resolved analysis of each single polarization mechanism contributing to the overall losses of the cell. The evaluated kinetic parameters (reaction orders of hydrogen, steam and the activation energy) in reformate are in the same size as under hydrogen operation. Obviously only hydrogen is directly electrochemically oxidized in reformate-fuelled cells. The higher overall polarization resistance compared to hydrogen operation has to be attributed to a newly identified low-frequency process, which is interpreted in this work. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3597177] All rights reserved.