Reversible addition-fragmentation chain transfer polymerization (RAFT) of styrene (St) was carried out in the presence of oxygen using 2-cyanoprop-2-yl 1-dithionaphthalate (CPDN) or benzyl (2-phenyl)-1-imidazolecarbodithioate (BPIC) as the RAFT agent. The characteristics of the "living"/controlled radical polymerization were observed at high concentration of RAFT agent and low polymerization temperature. A slight increase in the rate of polymerization was found when oxygen was added at high concentration to the polymerization system; however, the presence of oxygen incurred greater polydispersities of the polymer at the same monomer conversion compared to that obtained in the absence of oxygen. The possible mechanism of the RAFT polymerization of St in the presence of oxygen was discussed. (c) 2007 Elsevier Ltd. All rights reserved.