Atom transfer radical polymerization (ATRP) of styrene was initiated by a poly(ethylene glycol) macroinitiator prepared by quantitative esterification of MPEG2000 with 2-chloropropionyl chloride. The polymerization carried out at 130 degrees C catalyzed by addition of cuprous chloride and 2,2＇-bipyridine has been found to comply to the criteria for a "living" polymerization, since a linear M-n versus monomer conversion plot was found in accordance with the theoretical line indicating essentially 100% initiating efficiency. Also the polymerization is first order with respect to monomer concentration determined in two independent ways. The polydispersity index remained around 1.3 throughout the polymerization and no formation of homopolystyrene could be detected.