Abstract: An anionic polymerization is carried out by polymerizing a monomer for anionic polymerization in a solvent in the presence of a polymerization initiator after preparing a polymerization system by an operation (I) adding a solution of an organometallic compound in a polymerization system of a solvent or a combination of a solvent and an inert gas and an operation (II) removing excess of the unreacted organometallic compound, before charging the monomer and the polymerization initiator.

Abstract: In the polymerization of an anionically polymerizable monomer using a polymerization system comprising a monomer and a polymerization solvent wherein an organometallic compound polymerization initiator, soluble in said polymerization system and having the formula:MeR.sub.xwherein Me is a metal selected from the group consisting of Groups I and II of the Periodic Table; R represents an alkyl or aryl group, or an aliphatic or aromatic hydrocarbon residue; and the integer x is 1 or 2; is added to said system, the improvement which comprises adding said organometallic compound as a solution comprising said organometallic compound dissolved in a high viscosity solvent having a viscosity higher than 1 cp at room temperature, and which dissolves slowly in said polymerization system.