ABA triblock copolymers of styrene and p-methylstyrene were prepared by living cationic polymerization using a bifunctional initiating system in the presence of 2,6-di-tert-butylpyridine, which, as a proton-trapping agent, suppressed the initiation by adventitious impurities and thus enhanced the Livingness of the styrene monomers. By using these characteristics, triblock copolymers of styrene and p-methylstyrene could be prepared easily. The polymers showed the same molecular weight as the theoretical value and narrow and unimodal molecular weight distributions (MWDs).