The effect of CuSCN as a catalyst in atom-transfer radical polymerization (ATRP) was investigated. CuSCN can successfully be used for the ATRP of MMA. Substituted bipyridines was well as imines can be used to stabilize the copper complex in solution. CuSCN induces faster polymerization compared to CuBr and CuCl when tosylchloride is used as the initiator. However, the polydispersity is larger than that obtained in the cases of CuCl and CuBr. Dependence of the molecular weights (filled symbols) and polydispersities (open symbols) of PMMA on the monomer conversion for the solution ATRP of MMA in p-xylene at 100 degreesC using ethyl-2-bromoisobutyrate (EBIB) as the initiator and NPPI aas the ligand. [MMA](0) = 5.37 M, [NPPI] = 0.017 M, [EBIB] = 0.043 M, [Cu(I)] = 0.043 M.