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The catalytic reforming of methane with carbon dioxide on Pd (∼1%)/R-Al 2 O 3 and Pd (∼1%)-CeO x /R-Al 2 O 3 catalysts was studied at 627 °C using a stoichiometric feed mixture. Characterization of fresh and used samples was carried out by TEM and TG analyses. Preliminary experiments in the 600-730 °C temperature range demonstrated that, on Pd/R-Al 2 O 3 , the conversion of CO 2 was larger than that of CH 4 because of the reverse water-gas shift (RWGS) reaction, although the CO/H 2 ratio was close to 1. This behavior is attributed to the predominant CH 4 decomposition reaction that leads to carbon deposition and catalyst deactivation. The decline in activity was also due to palladium sintering, a process favored by the reducing atmosphere generated by the presence of CO and H 2 . Kinetic information obtained in experiments carried out under differential conditions was used to evaluate the importance of mass-and heat-transport limitations. It is shown that intraparticle mass transfer and interparticle heat resistances can be controlled by using small catalyst particles and diluting the catalyst bed with an inert solid, respectively. On the other hand, gas-solid temperature gradients are expected if the reforming reaction is carried out at >600 °C at low flow rates. The catalytic activity, selectivity, and stability of Pd/R-Al 2 O 3 and Pd-CeO x /R-Al 2 O 3 were tested in 24-h runs. It was found that a Pd/R-Al 2 O 3 sample with an average particle size of 5 nm exhibits an initial activity comparable to that of Pt/ZrO 2 catalysts and a high and constant selectivity to H 2 (CO/H 2 ≈ 1). However, the catalytic activity decreased by 50% after a reaction time of 24 h due, in part, to metal sintering but mainly to carbon formation. A presintered Pd/R-Al 2 O 3 sample with an average particle size of 19 nm deactivates more rapidly because of a rapid accumulation of carbon deposits. The process of carbon deposition can be suppressed to a very large extent by Ce addition, although the CO/H 2 ratio becomes larger (CO/H 2 ≈ 1.3). In addition, the presence of Ce reduces the sintering process.