With advances achieved in the area of microreactor technology, new possibilities for the use of microchannel reactors in the field of heterogeneous catalysis are now attainable. By exploiting these microstructured reactors for their relatively high surface-to-volume ratio and the inherent safety due to dimensions below the quenching distance at which explosions can propagate, hazardous reaction mixtures can be handled safely. The aim of this paper is to present the results on the catalytic H-2/O-2 reaction obtained from an alumina-coated microstructured reactor/heat exchanger that has been impregnated with a platinum catalyst. With this reactor, explosive mixtures of gaseous hydrogen and oxygen (up to 50% by volume of H-2 in O-2) were safely handled and the hydrogen was completely converted to water without explosions by maintaining a heterogeneously catalyzed reaction. The homogeneous reaction was prevented through efficient removal of the heat evolved from this highly exothermic reaction with cooling gas flowing in the heat exchanger channels of the reactor. It is anticipated that the use of microstructured reactors in catalysis research will add new levels of safety and control in studying chemical systems that necessarily involve explosive mixtures of gases.