The importance of inlet region of rotating packed bed (RPB) was confirmed recently. This enlightened us to design another novel reactor, named rotor-stator reactor (RSR), which has multiple inlet regions along radial direction. The micromixing efficiency of RSR was studied by adopting the iodide-iodate reaction as working system. The effects of operating conditions (e.g. rotor speed and reagent concentration) on micromixing efficiency (characterized by segregation index X-S) were investigated. In addition, the effects of different rotor-stator combinations as well as the amount of rotor- and stator-ring on micromixing efficiency were also considered. Based on the incorporation model, the micromixing time of RSR was estimated to reach about 10(-5) s, which is less than that of rotating packed bed (about 10(-4) s). (c) 2006 Elsevier B.V. All rights reserved.