The anionic polymerization of 4-cyano-alpha-methylstyrene (1) was carried out in THF at -78 degrees C with (1,1,4,4-tetraphenylbutanediyl) dipotassium and -dilithium, ( diphenylmethyl)potassium, and (triphenylmethyl)potassium, and cesium. slum. All the polymerizations of 1 quantitatively proceeded with each initiator, although the rates of polymerization were quite slow, especially in the case of organolithium initiator. The resulting poly(1)s always possessed narrow molecular weight distributions (M(W)/M(n) <1.13) and predicted molecular weights based on the molar ratios of monomer to initiators. The living nature of the propagating carbanion derived from 1 was demonstrated by the postpolymerization. Novel well defined block copolymers poly(1-b-styrene-b-1) and poly(1-b-tert-butyl methacrylate-b-1) were successfully synthesized by the sequential addition of 1 and styrene or tert-butyl methacrylate.