The terpolymer of acrylamide (AM), dimethylaminoethyl methacrylate methyl chloride (DMC), and acrylic acid (AA) was synthesized with their molar ratio of 70 : 15 : 15 through dispersion polymerization in aqueous solution of ammonium sulfate (AS), using poly(dimethylaminoethyl methacrylate methyl chloride) (PDMC) as stabilizer and 2,2'-azobis(2-amidinopropane) dihydrochloride (V-50) as initiator. The particle size of the terpolymer ranged from 5 to 8 mu m and the intrinsic viscosity was from 5.5 to 11.6 dL g(-1). The terpolymer had anti-polyelectrolyte effect under low AS concentration, but polyelectrolyte effect with the concentration beyond 10%. Polymerization dispersion with low apparent viscosity, uniform particles, good stability, and high molecular weight terpolymer was obtained in single stage. The effects of varying concentrations of salt, stabilizer, and monomers on particle morphology and intrinsic viscosity were investigated. With increasing concentration of AS and PDMC, the intrinsic viscosity of terpolymer increased, then decreased afterward. However, it increased gradually with increase in monomer concentration. The particle size was enlarged with increasing of AS and monomer concentration and decreasing of PDMC concentration. The optimum condition was the concentrations of salt, stabilizer, and monomers 28%, 3.0%, and 8% to 15%, respectively. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 115:1131-1137, 2010