The preparation of homogeneous initiators having active sites at both ends and the polymerization of isoprene by oligomeric dilithium initiator in benzene were studied.Metallic lithium was allowed to react with naphthalene in diethyl ether. We removed insoluble residues from reaction products, added styrene or isoprene, and then completely removed diethyl ether and added benzene. We found that by doing so, the obtained solutions were substantially free from ether and were readily soluble in nonpolar solvents to form a homogeneous solution of an initiator.The relationship between the number-average molecular weight and the ratio of monomer concentration to initiator concentration in the reaction of oligomerization suggested that the propagation species would be at both polymer ends.The polymerization of isoprene by oligomeric dilithium initiator in benzene was homogeneous and had no induction period.It was found that the increase in yield was linear with time and the yield and the monomer concentration had no effect on the microstructure of poloisoprene.The molecular weight distribution of the oligomeric initiator and polymer was very narrow.A test piece prepared from the polymer obtained in this reaction by the standard rubber compound method had good mechanical properties.