A mathematical model was developed for the ethylene epoxidation reaction over a cesium-doped silver catalyst in a packed-bed membrane reactor (PBMR) and compared with the experimental results. The dusty gas model, based on the Maxwell-Stefan equations, was used to describe transport through the porous stainless-steel membrane. Two reactor configurations were investigated where either oxygen (PBMR-O) or ethylene (PBMR-E) permeated through the membrane, with the co-reactant fed to the catalyst bed. The model results were ill good agreement with the experimental data. Simulations showed that the imposed pressure gradient resulted in predominantly convective flow through the membrane, which inhibited backdiffusion of components: from the catalyst bed. The variables studied included reaction temperature and inlet reactant concentrations. The model results, as also demonstrated experimentally, confirmed that the PBMR-E is the best configuration, followed by the conventional fixed-bad reactor (FBR) and the PBMR-O, respectively.