We have conducted reversible addition-fragmentation chain transfer ( RAFT) polymerization of n-hexyl methacrylate solubilized in a microemulsion using dodecyltrimethylammonium bromide as surfactant and 2-cyanoprop-2-yl dithiobenzoate ( 1) as the RAFT agent. The resulting latex particles are stable and much smaller, ranging from 18 to 30 nm depending on the mole ratio of RAFT agent 1 to the free radical initiator,2,2'-azobis(2-amidinopropane) hydrochloride (V50), than those produced by conventional microemulsion polymerization. The molecular weight increases linearly with conversion, and the polydispersity remains low when the number of RAFT agent molecules used is in excess of the initial number of swollen micelles. The RAFT technique can be successfully used in microemulsion polymerization to produce stable dispersions of small particles containing low molecular weight polymers. This is believed to be the first report of RAFT polymerization in microemulsion.