For the first time, ligand-free Cu(0)-mediated polymerization of methyl methacrylate (MMA) was realized by the selection of ethyl-2-bromo-2-phenylacetate as initiator at ambient temperature. The polymerization can reach up to 90% conversion within 5 h with dimethyl sulfoxide (DMSO) as solvent, while keeping manners of the controlled radical polymerization. Extensive investigation of this system revealed that for a well-controlled Cu(0)-mediated polymerization of MMA, the initiator should be selected with the structure as alkyl 2-bromo-2-phenylacetate, and the solvent should be DMSO or N,N-dimethylformamide. The selectivity for solvents indicated a typical single-electron transfer-living radical polymerization process. Scanning for other monomers indicated that under equal conditions, the polymerizations of other alkyl (meth)acrylates were uncontrollable. Based on these results, plausible reasons were discussed. The ligand-free Cu(0)-mediated polymerization showed its superiority with economical components and needless removal of Cu species from the resultant products. (c) 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 50: 711-719, 2012