The fine emulsion polymerizations of styrene initiated by a redox system ammonium peroxodisulfate/sodium thiosulfite stabilized by a non-ionic emulsifier were kinetically investigated. The dependence of the rate of polymerization on conversion or the emulsifier concentration was described by a curve with maximum at medium conversion. The maximum rate of polymerization is proportional to the - 0.45(th) and 1.5(th) power of initiator and emulsifier concentration, the number of particles to the 0.32(nd) and 1.3(rd) power of initiator and emulsifier concentration and the molecular weight to the 0.62(th) and -0.97(th) power of initiator and emulsifier concentration, respectively. The results show a strong decrease in turbidity at around 20% conversion when emulsion turns into translucent latex. Deviation from the micellar nucleation model was attributed to the solubility of emulsifier in monomer, high level of nonmicellar aggregates, thick interfacial layer and transfer emulsion to microemulsion. The strong decrease of molecular weight with increasing emulsifier concentration is attributed to chain transfer events promoted by the high level of emulsifier at the reaction loci.