Miniaturization is fast gaining importance and relevance in chemical processes that are conventionally carried out on a lab-scale or larger. Miniaturized chemical-reaction systems, or microreactors, are devices that behave as continuous flow systems and whose dimensions are in sub-millimeter range. Microreactors were successfully fabricated using wet silicon bulk micromachining and deep reactive ion etching (DRIE) techniques, were used to characterize reactions involving heterogeneous catalysis, and demonstrated their feasibility as efficient tools in catalyst and process development. In this study, the relatively simple reactions of cyclohexene hydrogenation and de-hydrogenation over a platinum catalyst were studied, reactions which are models for important classes of reactions of significance in petroleum industry. The conversion, selectivity and yield for products cyclohexane and benzene, were measured as a function of temperature and reactant flow rates. The experiments were done in microreactors of characteristic dimensions of 100 and 5 mum. The results are shown which compare the performance of these two types of reactors. (C) 2002 Elsevier Science B.V. All rights reserved.