An electrolyte supported solid oxide fuel cell (SOFC) was continuously operated with hydrogen, methane, and bioethanol for nearly 400 hours without adding water, O-2, or CO2, and delivering a rather stable power output. Such a fuel-flexible SOFC was achieved by using both an anodic catalytic layer, which efficiently converts the primary fuel into hydrogen, and by the operation in gradual internal reforming conditions, which prevented degradation due to carbon formation. (C) 2014 The Electrochemical Society. All rights reserved.