ln the presence of beta-cyclodextrin (beta-CD), reversible addition-fragmentation chain transfer (RAFT) polymerization has been successfully applied to control the molecular weight and polydispersity [weight-average molecular weight/number-average molecular weight (M-w/M-n)] in the miniemulsion polymerization of butyl methacrylate, with 2-cyanoprop-2-yl dithiobenzoate as a chain-transfer agent (or RAFT agent) and 2,2'-azoisobutyronitrile (AlBN) as an initiator. beta-CD acted as both a stabilizer and a solubilizer, assisting the transportation of the water-insoluble, low-molecular-weight RAFT agent into the polymerization loca (i.e., droplets or latex particles) and thereby ensuring that the RAFT agent was homogeneous in the polymerization loca. The polymers produced in the system of beta-CD exhibited narrower polydispersity (1.2 < M-w/M-n < 1.3) than those without beta-CD. Moreover, the number-average molecular weight in the former case could be controlled by a definite amount of the RAFT agent. Significantly, beta-CD was proved to have a favorable effect on the stability of polymer latex, and no coagulum was observed. The effects of the concentrations of the RAFT agent and AIBN on the conversion, the molecular weight and its distribution, and the particle size of latices were investigated in detail. Furthermore, the influences of the variations of the surfactant (sodium dodecyl sulfate) and costabilizer (hexadecane) on the RAFT/miniemulsion polymerization were also studied. (c) 2005 Wiley Periodicals, Inc.