A method for estimating gas permeability through a zeolite membrane, using a molecular simulation technique and a theoretical permeation model, is presented; The estimate of permeability is derived from a combination of an adsorption isotherm and self-diffusion coefficient based on the adsorption-diffusion model. The adsorption isotherm and self-diffusion coefficients needed for the estimation were calculated using conventional Monte Carlo and molecular dynamics simulations. The calculated self-diffusion coefficient was converted to the mutual diffusion coefficient and the permeability estimated using the Fickian equation. The method was applied to the prediction of permeabilities of methane and ethylene in silicalite at 301 K. Calculated permeabilities were larger than the experimental values by more than an order of magnitude. However, the anisotropic permeability was consistent with the experimental data and the results obtained using a grand canonical ensemble molecular dynamics technique (Pohl et al. Mel. Phys. 1996, 89 (6), 17.5-1731).