Silicalite, ZSM5, and mordenite membranes were prepared on alumina and stainless steel porous tubes by several procedures. The N-2 permeation flux was measured before and after exposure to water, n-octane, or n-butane under different conditions (capillary condensation and adsorption). The reduction of permeation flux that takes place in the presence of adsorbable compounds can be related to the quality and separation properties of a given membrane. Also, a good correlation was observed between the separation selectivity and the time required to reach steady state after exposure of the membrane to quasi-saturation conditions. Both measurements can be used as fast and reliable techniques for membrane characterization.