Reversible addition-fragmentation chain transfer (RAFT) polymerization of a typical hydrophobic monomer of styrene within microreactor of shell-corona hollow microspheres of poly(styrene-co-methacrylic acid) suspending in water is studied. The shell-corona hollow microspheres contain a hydrophilic corona of poly(methacrylic acid) (PMAA) and a cross-linked polystyrene shell, which can suspend in water because of the hydrophilic corona of PMAA. The size of the shell-corona hollow microspheres is about 289 nm and the extent of the microcavity of the hollow microsphere is 154 nm. These shell-corona hollow microspheres can act as microreactor, within which the typical hydrophobic monomer of styrene, the RAFT agent of S-benzyl dithiobenzoate and the initiator of 2,2'-azobisisobutyronitrile can be encapsulated and RAFT polymerization of styrene takes place in well controlled manner in water. It is found that the resultant polymer of polystyrene has a competitively low polydispersity index and its number-average molecular weight linearly increases with monomer conversion. The method is believed to be a new strategy of RAFT polymerization of hydrophobic monomer in aqueous solution. (C) 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 5446-5455, 2010