The development of microreactors for the catalytic reforming of fuels, such as methanol and hydrocarbons, for on-site H2 production has grown rapidly in the past few years. The challenges encountered in the reforming of fuels are: (i) to avoid coking of the catalyst by operating at temperatures greater than 800 °C; (ii) to achieve high conversion in a small reactor volume; and (iii) to minimize the pressure drop across the reactor. A suitable microreactor, to meet these challenges, must be compatible with high operating temperatures, have a high surface area-to-volume ratio, and have a high porosity. To meet these requirements, we have fabricated highly porous inverted beaded catalyst monoliths made from silicon carbide (SiC) and silicon carbonitride (SiCN), and have integrated these structures within high-density, non-porous alumina housings. The integrated ceramic microreactors show excellent thermal and chemical stability up to 1200 °C in air, and the SiC or SiCN monoliths have geometric surface areas between 105 and 108 m2/m3. The void fraction of 0.74 significantly reduces the pressure drop compared to packed catalytic beds (Advanced Functional Materials, 2005, 15, 1336-1342). Characterization of these microreactors using ammonia decomposition at temperatures up to 1000 °C showed that Ru catalyst supported by SiC enhances its catalytic activity compared to Ru on alumina or silica (J. Catalysis, 2006, accepted). We will also report the steam reforming of propane using the same Ru/SiC monoliths at temperatures above 800 ºC. The monoliths throughout these studies show exceptional stability and retention of activity. Coking can be avoided since they can be operated above 800 ºC.