The effect of incorporating a small amount of alkali metal alkoxides into a diene polymerization catalyzed by n-butyllithium in the presence of a polar modifier was investigated. It was found that the addition of sodium alkoxide significantly enhanced the polymerization rate of the monomers (1,3-butadiene, isoprene and styrene) and increased the vinyl content of the resulting polymers. It was also found that almost any sodium salt of an alcohol (cyclic or acyclic alcohols) or alkylphenol provided the similar 'synergistic' effects of improving polymerization rate and the vinyl content of polymer product. The rate enhancement was attributed to the super basicity from a superbase generated with sodium alkoxide and organolithium. Since other heavier alkali metal alkoxides, such as potassium or cesium alkoxide did not exhibit the similar synergistic effects, it suggested that only sodium is small enough to form a complex with lithium which can coordinate effectively with the polar modifier to yield high vinyl structures. The polymers prepared using the current catalyst system are branched which may have resulted from the backbone metallation by sodium metal or the superbase involved in the catalyst system. Since the current catalyst system is not monomer-specific, a variety of high vinyl elastomers containing diene(s) with or without vinyl aromatic monomers can be prepared at very fast rates.