Analytical chips to lower the cost and increase the effectiveness of chemical analyses, well proven in biochemical and biomedical applications, have a bright future for organic and inorganic reaction analyses. We demonstrate the use of microfabricated catalytic reactors constructed with silicon wafer technology for catalytic hydrocarbon conversion. The details of fabricating the devices are presented, as is the configuration for using them to characterize a heterogeneous gas-solid catalytic reaction. We present the results of a study of the reaction of cyclohexene in the presence of hydrogen over a platinum thin-film catalyst. In this experiment, we determined what factors affect the selectivity of the conversion to either cylcohexane (hydrogenation) or benzene (dehydrogenation). A reactor model based on published rate law data corroborated the behavior of the reactors for operation below 120degreesC. We verified literature reports of the decline of activity with temperature and observed a simultaneous shift in selectivity. These experiments demonstrate the value of microreaction devices for acquiring data traditionally taken by bulkier, more costly, and less efficient, bench-scale reactors.