Abstract: A process for separating ethane and other higher hydrocarbons from a natural or produced gas stream, having methane as its major constituent. A rubbery permselective membrane, having a propane/methane selectivity of 8 or above, is contacted on its feed side with a gas mixture typically containing methane, ethane, propane, butane, and small amounts of other hydrocarbons, water vapor, hydrogen sulfide and carbon dioxide. Carbon dioxide, water vapor, ethane and the other higher hydrocarbons permeate preferentially through the membrane, and the retentate stream is correspondingly enriched in methane.