A series of samaria-doped ceria (SDC) supported Ni-Cu catalysts have been employed to carry out steam reforming of methane at 673-823 K without or in the presence of carbon dioxide. Results show that hydrogen can be produced from H2O dissociation over SDC and SDC supported Ni and Cu catalysts. The activity of H2O dissociation over Cu is higher than that over Ni. Carbon dioxide (CO2) has the ability to oxidize various NiCu/SDC catalysts. The order Of CO2 dissociation reactivity over various Ni-Cu/SDC catalysts is the same as that of steam reforming of methane with or without the presence of carbon dioxide. Ni-Cu interaction enhances the activity of steam reforming of methane. Cu enhances the water-gas shift activity in the presence Of CO2 and this enhancement effect may be quantitatively related to the amount of the Cu-Ni species. The methane conversion rate of steam reforming increases as the CO2 content in the feed increases. With increasing CO2 content, H2O conversion rate decreases but hydrogen (H-2) production rate increases in CO2-steam reforming; in addition, the net CO2 production rate decreases but the carbon production rate increases quite extensively. The presence of CO2 thus requires special attention to the problem of carbon deposition during internal reforming of methane. (c) 2006 Elsevier B.V. All rights reserved.