The catalytic production of synthesis gas through methane reforming using carbon dioxide was studied in a plug flow reactor and a membrane reactor at atmospheric pressure over nickel supported on MgO and La2O3. The Ni0.03Mg0.97O and the Ni/La2O3 catalysts exhibited high activity and gave conversions of methane at equilibrium levels in the plug flow mode of operation. Incorporation of a Vycor glass membrane in the reactor resulted in higher conversions than obtained in an identical plug flow reactor operated without diluent. The catalysts had low to moderate surface areas and low uptakes of H-2 and CO at room temperature. X-ray diffraction showed that there was no discernable change between the catalysts before and after reaction. Elemental analysis showed that there was little carbon deposited on the Ni0.03Mg0.97O catalyst but there was slight coking on the Ni/La2O3 catalyst.