A comprehensive theoretical analysis has been carried out to study the effect of microwave heating on a first order endothermic reactions. The mathematical model considers detailed description of microwave power absorption along with transport of heat and mass within the reacting domain. The effect of microwave heating on the progress of the endothermic reaction has been analyzed in terms of spatial nonuniformities as well as overall progress of the reaction compared to the case of conventional heating. The analysis is carried out for all possible spectrum of microwave power absorption, which enables us to quantify the effect of microwave heating in terms of percentage savings of reaction time. The detail mathematical model also allows to identify and study the effect of various parameters responsible for describing the interaction between the heat and mass transport in presence of volumetric heating. A systematic and thorough analysis on the effect of these parameters demonstrate an interesting regime, where volumetric heating may not yield better progress than conventional heating. (C) 2011 Elsevier Ltd. All rights reserved.