Polyolefin compositions comprising: (A) 20 to 50 parts by weight of a particular propylene polymer having a MWD greater than 3.5; and (B) 50 to 80 parts by weight of an elastomeric ethylene copolymer having a low enthalpy of fusion and a narrow MWD. The compositions of the invention are capable of giving, after dynamic vulcanization, thermoplastic elastomeric products having optimum elastomeric properties and a good balance of physico-mechanical properties.