A general method for the transformation of "living" carbocationic into "living" radical polymerization, without any modification of chain ends, is reported for the preparation of ABA block copolymers. For example, alpha,omega-difunctional polyisobutene, capped with several units of styrene, Cl-St-PIB-St-Cl, prepared cationically (M-n = 7800, M-w/M-n = 1.31) was used as an efficient difunctional macroinitiator for homogeneous "living" atom transfer radical polymerization to prepare triblock copolymers with styrene, PSt-PIB-PSt (M-n = 28,800, M-w/M-n = 1.14), methyl acrylate, PMA-PIB-PMA (M-n = 31,810, M-w/M-n = 1.42), isobornyl acrylate, PIBA-PIB-PIBA (M-n = 33,500, M-w/M-n = 1.21), and methyl methacrylate, PMMA-PIB-PMMA (M-n = 33,500, M-w/M-n = 1.47).