Kinetics of chemical oxidative dispersion polymerization of 3,5-xylidine (Xy) in aqueous medium with ammonium persulfate (APS) as an oxidant was studied by monitoring the amount of proton released from Xy monomer, which was obtained from the amount of potassium hydroxide (KOH) solution added to keep constant pH values using a pH stat. The initial polymerization rate (R) [mol/L/min] of Xy was expressed as follows: R = 1.65 (1 - alpha) [Xy] [APS], where alpha is the degree of ionization of Xy, and [Xy] and [APS] are concentrations of Xy and APS, respectively.