In this study, the adsorption equilibria and kinetics of pure propane (C3H8) and propylene (C3H6) on natural erionite (ERI), from Agua Prieta (Sonora, Mexico), and on cation-exchanged erionite samples (K-ERI and Ag-ERI) have been measured at different temperatures using a glass high-vacuum volumetric device. All of the samples showed selectivity toward propylene. The ion-exchange treatment influenced, remarkably, the C3H8 and C3H6 adsorption behaviors. The adsorbed amounts of both hydrocarbons on K-ERI and Ag-ERI samples were lower than those on ERI, a result that can be ascribed to a decrease in micropore volume. It was established that the adsorptive separation of these gases on K-ERI could be effected most efficiently at 111 degreesC for gas-adsorbent contact times in the range 20-100 s, whereas the Ag-ERI sample could be recommended for this separation for the temperature range 50-80 degreesC and for short gas-adsorbent contact times in the interval 10-30 s.