A proton-conducting solid-state electrolyte composed of Li2SO4 has been tested in a medium temperature (similar to 700 degrees C) fuel cell with H2S as the fuel. Proton conductors are preferred over oxide-ion conductors for the elimination of SO2 as a possible product of the oxidation of H2S. This electrolyte, Li2SO4, had been previously used with H-2 as the fuel; its thermodynamic stability in H2S makes it a natural choice for this application. Here we report, with first, crudely prepared electrolytes, open-circuit voltages of above 1 V, with short-circuit current densities of above 10 mA/cm(2).