The homogeneous reverse atom transfer radical polymerization (ATRP) of styrene was initiated by benzoyl peroxide (BPO) in the presence of CuBr or CuBr2 complexed by 4,4＇-di(5-nonyl)-2,2＇-bipyridine (dNbpy). In contrast to the successful reverse ATRP initiated by azobis(isobutyronitrile) (AIBN) and CuBr2/2dNbpy, no control of polymerization was observed for the BPO/CuBr2/2dNbpy system. However, controlled/"living" polymerization was observed when BPO was used together with CuBr/2dNbpy. The differences between the BPO and AIBN systems are ascribed to the electron transfer and the formation of copper benzoate species.