This review addresses the catalytic reactions performed in microstructured reactors, which are more and more recognized in recent years as a novel approach for chemistry and chemical process industry. They are particularly suited for highly exothermic and fast reactions allowing temperature control and isothermal operation. A brief evaluation of the advantages for gas-phase, liquid-phase, and gas-liquid-solid reactions carried out in miniaturized devices is discussed. Alternative designs to achieve microstructured fluid patterns, besides microfabrication, are also described. (c) 2005 Elsevier B.V. All rights reserved.