The performance of a Ni/Ce0.75Zr0.25O2 catalyst for the autothermal reforming of isooctane is evaluated and compared using typical packed bed reactors, steel microreactors, and quartz microreactors. Microchannel reactor systems have in recent years been proposed as attractive alternatives to traditional catalytic packed bed reactors due to their improved heat and mass transfer properties. The microreactors employed in this study are comprised of stackable layers, with FeCrAlloy metal foams serving as catalyst substrate. To deploy the Ni/Ce0.75Zr0.25O2 catalyst in the microreactors, the metal foam substrates were coated with a catalyst washcoat formulation. Several factors are discussed that may influence the microreactor performance, with emphasis on the different contributions of heat transfer mechanisms between the active reaction zone and its surroundings, the materials of construction, and reactor aspect ratio. Heat effects were found to be particularly important in determining performance for the steel microreactors. (c) 2005 Elsevier B.V. All rights reserved.