Single molten carbonate fuel cells (MCFCs), with an effective electrode area of 256 cm(2) and state-of-the-art components, are run at 150 mA cm(-2) under atmospheric pressure for 15 000 and 40 000 h, then the components are analyzed for material degradation. Cell output is reduced due to a short-circuit induced by dissolution of the NiO cathode, increase of LR-drop, and increase of anode and cathode polarization. It is concluded that the main factors that limit the life of the materials are dissolution of the NiO cathode and the degradation of LiAlO2 matrix.