The effect of stirring rate on control/livingness and particle formation in emulsifier-free organotellurium-mediated living radical emulsion polymerization (emulsion TERP) of styrene at 60 degrees C was investigated at two stirring rates (220 and 1000 rpm), in which styrene phase floated as a layer on an aqueous phase at 220 rpm or dispersed as droplets at 1000 rpm. A water-soluble TERP agent, poly(methacrylic acid) (PMAA)-methyltellanyl (PMAA(30)-TeMe) (degree of polymerization of PMAA, 30), and a water-soluble thermal initiator, 4,4'-azobis(4-cyanovaleric acid), at high pH were used. The polymerization rate was not affected by the stirring rate, but the control/livingness was significantly improved when the stirring rate was increased from 220 to 1000 rpm. This difference would be caused by a larger amount of consumed PMAA(30)-TeMe in the aqueous phase and higher monomer concentration inside polymerizing particles as polymerization loci at 1000 rpm than at 220 rpm. The stirring rate also affected the particle size distribution: both nanometer-sized and submicrometer-sized particles were prepared at 220 rpm, and mainly nanometer-sized particles were prepared at 1000 rpm. From these results, it is concluded that the stirring rate is an important parameter in emulsion TERP to obtain good control/livingness and control particle formation.