Many important industrial processes currently employ synthetic zeolites as catalysts. Fixed and fluidized bed reactors, employed in most commercial applications, use catalyst pellets formed from mixtures of zeolite crystals and binders. However, binders hinder access to the zeolite active sites; thereby reducing catalytic efficiency. This study demonstrates that zeolites synthesized in situ on monolithic substrates offer lower resistance to mass transfer. The controlling mass transfer regime in these reactors is assessed from experimental and theoretical studies of two test reactions in ZSM-5 coated monolithic reactors. Also, the applicability of the monolithic reactor configuration to other zeolite catalyzed processes is discussed.