Silica-polystyrene core-shell particles were successfully prepared by surface-mediated reversible addition fragmentation chain transfer (RAFT) polymerization of styrene monomer from the surfaces of tile silica-supported RAFT agents. Initially, macro-RAFT agents were synthesized by RAFT polymerization of gamma-methacryloxypropyltrimetboxysilane (MPS) in the presence of chain transfer agents (CTAs). Immobilization of CTAs onto the silica surfaces was then performed by reacting silica with macro-RAFT agents via a silane coupling. Grafting of polymer onto silica forms core-shell nanostructures and shows a sharp contrast between silica core and polymer shell in the phase composition. The thickness of grafted-polymer shell and the diameter of core-shell particles increase with the increasing ratio of monomer to silica. A control experiment was carried out by conventional free radical emulsion copolymerization of MPS-grafted silica and styrene under comparable conditions. The resulting data provide further insight into the chemical composition of grafted-polymers that are grown from the silica surface through RAFT process. (C) 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 467-484, 2009