Aqueous polymerization of methyl methacrylate (MMA) initiated by potassium persulfate-thioglycollic acid (TGA) redox system has been studied at 30°C under nitrogen atmosphere. The rate of polymerization is expressed byThe polymerization was studied over the temperature range 20–45°C. The activation energy calculated from an Arrhenius plot was found to be 8.34 kcal/mol (34.9 kJ/mol). The effects of inorganic electrolytes and organic solvents on polymerization were also investigated. Except for manganese sulfate and sodium oxalate, all of them depressed both the initial rate and the limiting conversion.