The rate at which molecules can pass one another inside the pores of crystalline microporous materials can be an important factor in determining the transport properties of these systems, particularly for materials with unidimensional pores. An efficient method for characterizing adsorbate passage in micropores is presented and applied to a variety of adsorbates in AlPO4-5. It is shown that adsorbate passage can be an activated process in some cases. The implications of rare adsorbate passage for the experimental characterization of tracer diffusion and for the flow of multicomponent mixtures through zeolitic membranes are briefly considered in the context of a simplified lattice gas model.