High-pressure adsorption of helium, neon, argon, nitrogen, krypton, and methane on zeolites 3A, 4A, 5A, and 13X was measured at room temperature up to 500 MPa. The corresponding isotherms are qualitatively comparable to those previously obtained with the same gases adsorbed on activated carbon. They are analyzed and compared to those calculated on the basis of the Ruthven thermodynamic model of adsorption on zeolites. The respective importance of the contributions of solid-gas and gas-gas interactions and the exact role of pores were established. Attractive forces involve the isotherm maximum whereas repulsive forces are predominant at high pressure and involve a slight reincrease of adsorption. As concerns the well-calibrated pores of zeolites, in addition to their molecular sieving effect, they contribute mainly to increasing the specific area.