The n-butyllithium/N,N,N＇,N＇-tetramethylethylenediamine system has been found to polymerize 1,3-cyclohexadiene to produce a "living" polymer having a narrow molecular weight distribution. Ternary block copolymers with narrow molecular weight distribution could be synthesized from 1,3-cyclohexadiene, styrene, and butadiene with very high efficiency. The relative reactivity of 1,3-cyclohexadiene, styrene, and isoprene in the copolymerization was found to be in the order styrene, isoprene, and 1,3-cyclohexadiene, In contrast, the relative reactivity of the propagating species of living poly(1,3-cyclohexadiene) was higher than that of the propagating species of living polystyrene.