The SP-PLP-EPR technique has been used to measure Cull mediated ATRP deactivation and Cu-I-mediated organometallic reactions for butyl acrylate (BA) polymerization. The deactivation rate is by more than 1 order of magnitude higher than in dodecyl methacrylate (DMA) polymerization, thus enabling well-controlled ATRP despite the enhanced BA propagation rate. The organometallic reaction of Cu-I with BA radicals was found to play a role only with highly active Cu catalysts, as demonstrated for the Cu/TPMA-mediated ATRP of BA.