Concentrated dispersions are used as coating dispersions for aqueous polymeric coatings, and characterization of the actual concentrated dispersions is an important in the pharmaceutical industry. The commonly used aqueous coating polymers are acrylic polymers and cellulose derivatives. We conducted a characterization study of polymethacrylate-based aqueous polymeric latexes for aqueous coating, Eudragit ® L30D-55 (A-latex) and Eudragit ® RL30D (C-latex), by electroacoustic method. Colloidal Vibration Current (CVI) is one of the most important parameters relating to dynamic electrophoretic mobility and zeta potential, so we evaluated this parameter first. Volume fractions ϕ of the latexes in concentrated dispersions affect the CVIs according to the theory of Dukhin et al. The A-latex and C-latex CVI * s which were corrected with regard to the effect of volume fraction by the theoretical equation were nearly constant independent of ϕ in the ranges >0.04 and >0.03, respectively.The zeta potentials and colloidal stabilities of the concentrated dispersions were evaluated using an electroacoustic method by altering the pH and salt concentration. A-latex strongly aggregated at and below pH 2.5 and at and beyond 0.06mol/L of electrolyte concentration. Regarding C-latex, instable dispersion was observed at 0.3 and 1mol/L of NaCl concentration. The total potential energy of interaction between pairs of latex particles was changed by altering the salt concentration in this dispersion based on DLVO theory. The experimental results of stability in the concentrated latex dispersions can be explained by the total interaction energies.