ABSTRACT The discovery and development of high trans styrene–butadiene rubber (SBR) is presented. High trans SBR is prepared using a novel polymerization initiator of a specific combination of a barium salt and organometallic compound in a hydrocarbon solvent. The trans-1,4 content of the polybutadiene repeat units is sufficiently high, at a low vinyl content, to result in a crystallizing rubber. As a result, high trans SBR has high green strength similar to natural rubber (NR). The barium-based initiating system allows the formation of copolymers between butadiene and styrene, in which the distribution of styrene repeat units is considerably more random than that obtained with an organolithium initiator alone. By a judicious selection of the two initiator composition and the styrene content in the copolymer, high trans SBR also exhibits good building tack, again similar to NR. The properties of high green strength and good building tack for high trans SBR are unique among common synthetic rubbers. As such, high trans SBR is an excellent candidate for use as a tire carcass rubber in radial ply tire construction. High trans SBR is also valuable in tire tread compositions, providing good abrasion resistance.