Atom transfer radical polymerization using AIBN/CuBr2/2dNbipy as the initiating system has been successfully carried out for styrene, methyl acrylate, and methyl methacrylate. Well-defined polymers with low polydispersities have been obtained. High apparent initiation efficiencies were observed for both styrene and methyl acrylate polymerizations at 110 degrees C. With an increase of the [AIBN](0)/[CuBr2/ 2dNbipy](0) ratio, apparent initiation efficiency decreased and polydispersity increased. Low initiation efficiencies were observed for the polymerizations of methyl methacrylate at both 110 and 90 degrees C, with higher polydispersities at higher temperature. The changes in polydispersity with respect to the changes in [AIBN](0)/[CuBr2/2dNbipy](0) ratio and the temperature can he explained by the differences in the rate of deactivation by the copper(II) halide species.