Sparteine was found to be an efficient ligand because when complexed with copper(I) halide it generated a homogeneous catalyst for the atom transfer radical polymerization of styrene or methyl methacrylate, which was initiated by (1-bromoethyl)benzene in the former case and by p-toluenesulfonyl chloride in the latter. The plots of ln([M](o)/[M]) versus time and molecular weight versus monomer conversion exhibited linear dependencies, which indicated that the concentration of the living centers throughout polymerization was constant. The polydispersities of polystyrene and poly(methyl methacrylate) in both the bulk and solution polymerizations were quite low. An induction time was observed during the bulk polymerization of styrene; however, it was absent during the solution polymerization.