In this work, Cu(0)-mediated copolymerization of methyl methacrylate (MMA) and styrene (St) was explored. The polymerization was carried out at 25 degrees C with N,N,N',N '',N ''-pentamethyldiethylenetriamine as ligand and N,N-dimethylformamide as solvent. The copolymerization proceeded successfully while demonstrating characteristics of "living"/controlled radical polymerization. On the basis of the H-1 NMR spectra, the reactivity ratios of MMA and St were calculated to be 0.545 and 0.507, respectively, indicating a random copolymerization. In the case of dimethyl sulfoxide as the solvent, the copolymerization was out of control. The selection of initiator and concentration of Cu(0)/ligand were also important to the controlled process.