Molten carbonate fuel cells with four alkali carbonate eutectic mixtures of Li2CO3/Na2CO3/K2CO3 in the proportions 62/0/38, 43/0/57, 43/32/25 and 52/48/0 (mol %), have been operated using electrolyte matrices fabricated by tape casting. When the ratio of electrolyte volume to matrix pore volume was optimized, all of the test cells gave similar good performance.