Reforming of CH4 with CO2 proceeds at 400 degreesC over a catalyst consisting of ruthenium metal and CcO(2) highly dispersed on mordenite. The catalyst, Ru-CeO2/MZ, is highly active for the reforming of CH4 under the conditions at which a carbon formation reaction is thermodynamically apt to take place. The reforming selectively forms H-2 and CO. An increase in the weight of the catalyst resulting from carbon deposits was scarcely observed. IR spectra for the catalyst indicate that the reforming proceeds via the formation of the intermediate species such as Ru-CO and Ru-CHx on the surface of ruthenium. The data of H-2 adsorption support the idea that ruthenium is highly dispersed in Ru-CeO2/MZ.