The CO2 reforming of methane to synthesis gas was performed over pentasil-type zeolite-supported Ni catalysts. High activity with high resistance to coke in the catalysts was confirmed by obtaining near equilibrium conversions of CO2 and methane as well as near equilibrium yields on CO and H-2 for over 140 h of reaction. Coke deposition on the catalysts for the CO2-reforming reaction was remarkably diminished with the addition of alkaline promoters such as K and Ca oxides. This was attributed to the formation of carbonate species on alkaline promoters, mainly Ca, located adjacent to Ni sites and to the dissociative adsorption of CO2 on an Ni surface by the addition of alkaline promoters.