The availability of inorganic membranes which can withstand high temperatures has resulted in a wide ranging opportunity for the application of membranes in chemical reactors. Increased conversions, better selectivity, milder operating conditions and decreased separation load are some of the attractive features which are going to promote membranes as chemical reactors in many established and novel reaction systems. Established and emerging technologies in ceramics, semiconductors and metal plating such as slip casting, electroless plating, sputtering, and chemical and electrochemical vapor deposition techniques are being successfully adapted in the laboratory scale to produce membranes with high permeabilities and improved separation factors. It should soon be possible to categorize membrane technologies for different types of reactions. Further advancements in modifying the surface of the membranes to tailor them to specific catalytic and separation requirements will greatly enhance the versatility of the membranes as chemical reactors and separators in the future. This article reviews various applications of membrane reactors with particular emphasis on their application in high-temperature gas-phase reactions.