A new two-component catalyst system consisting of an immobilized catalyst and a soluble catalyst in ppm quantities was applied to atom transfer radical polymerization (ATRP). A high conversion of monomer (>90%) was achieved with a predetermined molecular weight and narrow molecular weight distribution (M-w/M-n = 1.1-1.3) in the ATRP of methyl methacrylate and methyl acrylate. The immobilized catalyst was removed by a filtration or sedimentation procedure. The casting of the reaction solution afforded clear and colorless polymer films. It was confirmed by the inductively coupled plasma (ICP) analysis that the residual amount of Cu in the resulting polymer was as low as 20 ppm.