The bulk autopolymerization of styrene (St) was successfully conducted in the presence of CuCl2 and 2,2'-bipyridine (bpy) at 110 and 130degreesC. We found that this polymerization was a living/controlled radical polymerization at a [St](0)/[CuCl2](0)/[bpy](0) ratio of 54:1:2.5. The resulting number-average molecular weights linearly increased with conversion, and the polyclispersity indices were very narrow (<1.5). The polymerization rate increased with temperature. Increasing the ratios (i.e., 129:1:2.5, 259:1:2.5, and 386:1:2.5) led to a decrease in the ability to control the autopolymerization of St, even uncontrolled polymerization (i.e., 643:1:2.5). The analysis of end groups by H-1-NMR indicated that the spontaneous generation of radicals from St were generated by a Mayo-type process, and this living/controlled radical polymerization might have underwent a reverse atom-transfer radical polymerization process. (C) 2003 Wiley Periodicals, Inc.