This invention relates to block polymers containing both crystalline and elastomeric blocks, the block copolymer having an A block and a B block. The A block is a polyethylene or an ethylene polymer optionally containing an alpha-olefin and is generally crystalline. The B block contains an ethylene, .alpha.-olefin copolymer segment and optionally contain an ethylene, .alpha.-olefin, non-conjugated diene terpolymer segment. If the B block contains a diene containing segment, the diene containing segment is furthest from the junction of the A and the B blocks. Also disclosed is a process for manufacture of the block copolymers and methods for coupling the block copolymers. Coupled block copolymers are useful as thermoplastic elastomers exhibiting physical properties approaching those of crosslinked EP or EPDM elastomers, but showing thermal processability after coupling. The block copolymers of the present invention may also be used as a lubricant or fuel additive, as a plastics blend component, in bitumen blends, as a component in hot melt adhesives and as a component of roof sheeting compounds.