Ni-Al2O3 catalyst activity was tested for methane steam reforming using two different reaction systems: a catalyst particle bed (0.420.5?mm catalyst particles diluted in SiC) with a surface area-to-volume ratio SA/V of 910?m1 and a porosity ? of 52?% and a catalyst-coated metal monolith with an SA/V of 3300 m1 and an ? of 86?%. Under a steam-to-carbon ratio of 2.5 and at a temperature of 700 degrees C, the highest specific reaction rates were found for the catalyst-coated monolith. The high SA/V and ?, together with the high rate of heat transfer of the metal monolith were found to be responsible of this optimum behavior. However, in both systems, the Ni-Al2O3 catalyst suffered a catalyst deactivation during operation.