Improved process for the sepn. of a gas stream contg. methane and components more volatile than methane, C2 components, C2 components and heavier hydrocarbon components, into (i) a volatile residue gas fraction contg. a major portion of the methane and components more volatile than methane, and (ii) a relatively less volatile fraction contg. a major portion of the C2 components, C3 components and heavier components, in which the process (a) the gas is cooled under pressure to provide a cooled stream; (b) the cooled stream is expanded to a lower pressure whereby it is further cooled; and (c) the further cooled stream is supplied to at least one fractionation section in at least one feed stream for fractionation at the lower pressure whereby the major portion of the C2 components, C3 components and heavier hydrocarbon components is recovered in the less volatile fraction; the improvement in which (d) a recycle stream is withdrawn from a region of the fractionation section below at least one of the feed streams; (e) recycle stream is compressed and thereafter the compressed recycle stream is cooled sufficiently to substantially condense it; (f) the condensed compressed recycle stream is expanded and thereafter supplied to the fractionation section at a top feed position; and (g) the quantity and pressure of the compressed recycled stream and the temps. of the feed streams are effective to maintain the overhead temp. of the fractionation section at a temp. whereby the major portion of C2 components, C3 components and heavier hydrocarbon components is recovered in the relatively less volatile fraction.    Also claimed is an improved apparatus to carry out the separation.    USE/ADVANTAGE -   Ethylene recoveries in excess of 99% can be obtained, the improved process making possible higher ethylene and ethane recoveries (up to several percentage points higher) than previous processes with the same energy requirements, the improved process being particularly suitable for processing feed gas contg. more than 10 mole % of components more volatile than methane, such as hydrogen, nitrogen etc..