The invention relates to thermoplastic elastomer compositions comprising a blend of a thermoplastic urethane polymer and a silicone composition, and to a process for forming a vulcanized thermoplastic elastomer composition. The thermoplastic elastomer composition comprises a blend of a thermoplastic organic polymer comprising a urethane polymer and (B) a silicone composition comprising (B1) a silicone base comprising (B1a) a diorganopolysiloxane gum having an average of at least 2 alkenyl groups per molecule and (B1b) from 1 to 50% by weight based on the diorganopolysiloxane gum (B1a) of a reinforcing filler, and (B2) an organohydrido silicone compound which contains an average of at least 2 silicon-bonded hydrogen groups per molecule, wherein the weight ratio of the thermoplastic organic polymer (A) to the silicone composition (B) is in the range 55:45 to 80:20.