AbstractIn an alkyllithium‐initiated polymerization of butadiene or styrene, dialkylzinc complexed with the initiator and effectively increased the initiation rate. This is particularly true with initiator of low solubility due to its very high state of aggregation. Dialkylzinc also complexes with the aggregated polymer‐lithium molecules to give a lower apparent solution viscosity. In the presence of a base such as tetrahydrofuran, diethylzinc served as chain‐transfer