The effect of polymerization temperature in emulsifier-free, organotellurium-mediated living radical emulsion polymerization (emulsion TERP) on the control/livingness and particle size distribution was investigated at 50, 60, and 70 degrees C. The size distribution of obtained particles was significantly affected by the polymerization temperature, that is, nanometer-sized particles at 50 degrees C, submicrometer-sized ones at 70 degrees C and both particles at 60 degrees C were obtained. At 60 degrees C the molecular weight distribution of the nanometer-sized particles was narrower than that of the submicrometer-sized ones. M-w/M-n at 70 degrees C was much high (4.6), on the other hand, it was 1.5 at 50 degrees C and a middle value (2.0) at 60 degrees C. When the polymerization temperature was changed from 50 to 60 degrees C during the emulsion TERP, the particle size distribution and control of molecular weight distribution were, respectively, similar to those at 50 degrees C. From these results, it is concluded that the particle formation by self-assembly nucleation in the early stage of the emulsion TERP is important for the formation of the monomodal nanometer-sized PS particles with good control/livingness