Adsorption isotherms are reported for Wa-mordenite and H-mordenite at several temperatures with a series of gas adsorptives above their critical temperature. The data sets are analyzed with the multiple equilibrium analysis (MEA) method [Drago, R. S.; et al. J. Am. Chem. Sec. 1998, 120, 538-547. Drago, R. S.; et al. J. Phys. Chem. B 1997, 101, 7548-7555], which produces equilibrium constants (Ki), capacities (ni), and thermodynamic parameters (enthalpies, Delta H-i, and entropies, Delta S-i) of adsorption for each process. The limited pore size distribution present in the zeolite mordenite presents an interesting comparison to the amorphous carbons studied previously by MEA [Drago,:R. S.; et al. J. Phys. Chem. B 1997, 101, 7548-7555]. The results of the MEA description of the adsorption data gathered for the interaction of an adsorbate (particularly, N-2, CO, and Xe) with Na-mordenite and H-mordenite are compared to other literature reports (including infrared spectroscopic studies and Monte Carlo simulations), and good agreement is found. In general, for adsorbates that can access the small channel (small adsorbates), three processes are required to describe adsorption. Two processes are required to describe adsorption for the larger adsorbates into the large (main) channel. The smaller total micropore volumes of Na- and H-mordenite for these adsorptives result in decreased capacity compared to that of the amorphous carbons. The process capacities from MEA (mol g(-1)) are converted to pore volumes using the calculated molar volume of the adsorbate, and the accessible surface area for a given process is converted with the excluded molecular area of the adsorbate. The results show that MEA provides a more detailed and accurate assessment of the interaction of admolecules with microporous solids, which addresses a matter of fundamental importance to researchers and practitioners-the interactions between gas-phase molecules and a surface of a condensed phase. This analysis leads to an increased understanding of this behavior in gas adsorption and catalysis.