The effect of temperature on the cathodic overpotential in a molten carbonate fuel cell (MCFC) has been investigated with a 100 cm(2) class single cell. The temperature range was from 823 K to 973 K under atmospheric conditions. Cathodic overpotential was measured using the inert gas step addition (ISA) and reactant gas addition (RA) methods. The cell successfully showed the overpotential at the very extreme temperatures of 823 K and 973 K. The results of ISA revealed that the cathode did not show clear dependence of gas-phase-transport-induced overpotential on the temperature. However, overpotential due to diffusion through the liquid electrolyte was significantly reduced by the temperature increase. The RA method revealed that most of the reduction could be attributed to the increase in the mass transfer of O-2 species. (C) 2013 Elsevier B.V. All rights reserved.