Monolith reactors have been widely used as catalytic converters in the automobile industry. Their applications in other fields, such as environmental pollution abatement and hydrocarbon processing for fuel cells, have also received much attention because of the unique advantages they can offer compared to packed-bed reactors. Detailed modeling and simulation can help understand the complexity of interactions between various physical and chemical processes occurring within monolith channels and in the channel walls. In this review, first a general monolith reactor model for gas phase reactions is proposed and discussed for various modeling applications. In the following sections, the recent published studies on modeling and simulation of gas; phase monolith reactors were reviewed with the focus on mass and heat transfer in monoliths, transient/dynamic modeling, gas flow uniformity and chemical kinetics effects on monolith reactor performance. Suggestions on future work were provided. Crown Copyright (C) 2008 Published by Elsevier B.V. All rights reserved.