Multiblock polymers were prepared by combination of ATRP (CuBr/tris[(2-pyridyl)methyl]amine) and RAFT polymerization involving cyclic trithiocarbonate (CTTC). In the combined polymerization system, the ATRP was introduced as constant radical source, CTTC underwent ring-opening polymerization, and the incorporated trithiocarbonate moieties derived from CTTCs performed as RAFT agent. Through the integrated process, multiblock polymers containing predictable average block number together with controlled molecular weight of the blocks were prepared by one-pot polymerization. The average block number of polymer was controlled by concentration ratio of CTTC to alkyl halide in ARTP, and the molecular weight of block were well regulated by concentration of CTTC and monomer conversion. (C) 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2425-2429, 2010