Zeolite membranes are normally grown on an inert support. In most exploratory studies on these membranes, it is hard to achieve ideal experimental conditions in which membrane support resistance and sorbate concentration on the permeate side are negligible. A simple pseudo-binary diffusion model is proposed for the gaseous transport in the support, while the generalized Maxwell-Stefan formulation is used to describe the zeolitic diffusion in the membrane. Based on these models, a simple graphical procedure is presented for analyzing the measured unary permeation flux data to obtain zeolitic diffusivity. Validation of the proposed procedure is demonstrated successfully on published experimental data.