Adsorption of pure methane, ethane and ethylene on molecular sieve zeolites was examined via the gas chromatographic method to determine the potential for the separation of ethylene from light hydrocarbons. The molecular sieves chosen for the study were H-mordenite and 13X, CaX, 4A and 5A zeolites. Henry＇s law constants were determined over a variety of temperature ranges between 233 and 473 K. van＇t Hoff plots are presented for all three gases on 4A and 5A zeolites and for methane and ethylene on the CaX and 13X zeolites and H-mordenite. Equilibrium separation factors for the ethylene/methane system are provided for all zeolites (except clinoptilolite) over various temperature ranges. Separation is most promising with CaX zeolite, which yielded separation factors ranging from 1100 at 100 degrees C to 100 at 200 degrees C. Separation seems possible in 5A and CaX zeolites at very high temperatures due to the strong affinity of their divalent cations for the ethylene pi-bond.