Diffusion in zeolites was studied by means of Monte Carlo methods and the generalized Maxwell-Stefan theory of irreversible thermodynamics. The influence of the surface occupancy, the surface structure, and the surface chemical potential on one- and multi-component surface diffusion was investigated. Mass transfer was simulated in one- and two-dimensional zeolitic channel structures. For the description of the sorption process two different models were applied, a Langmuir model and a model with repulsive interactions between sorbed molecules. The one-component Fick diffusion coefficient, in the case of the Langmuir adsorption model, was found to be independent of the surface occupancy and depended weakly upon the dimension of the lattice. Tracer diffusion on a one-dimensional lattice exhibited a linear dependence between the mean square displacement of labeled molecules and the square root of time. The mean square displacement in the case of tracer diffusion on the two-dimensional lattice obeyed the Einstein relation. The uptake behavior of binary mixtures, co- and counter-diffusion, upon the two-dimensional lattice as obtained from the Monte Carlo simulations was in agreement with a single-file diffusion model. The single-file diffusion matrix could be considered to be a limiting case of the generalized Maxwell-Stefan formulation. The results of the Monte Carlo simulations and the single-file diffusion model showed that the zeolitic structure had an influence on mass transfer rates in tracer flow and counter-diffusion. A coupling between surface fluxes present in the case of the transient uptake of a multi-component mixture was demonstrated. Monte Carlo Simulations of Diffusion in Zeolites and Comparison with the Generalized Maxwell-Stefan Theory. L.J.P.Van Den Broeke, S.A.Nuhuis, R.Krishna: Journal of Catalysis, 1992, 136[2], 463-77