Polarization measurements have been made on individual electrodes in operating molten carbonate fuel cells by using a third idling electrode. Hydrogen was supplied to the anode and an air‐carbon dioxide mixture to the cathode. Overvoltages as a function of time from 10−6 to 100 sec after current interruption have been recorded. Analyses of these curves indicate that total electrode polarization is the result of several factors: (a) ohmic polarization caused by electrolyte restrictions between the matrix and the electrode, (b) electrode coverage by reactant and products, (c) concentration gradients of potential determining species in the electrolyte. No activation polarization was observed at either electrode.