Surface characterization of poly(n-butyl methacrylate) (PBMA) core-shell latex particle with a shell rich in carboxylic acid groups has been investigated by means of potentiometric and conductometric titrations. PBMA core-shell latex particle was prepared by semicontinuous three-stage emulsion polymerization. Methacrylic acid (MA) was added at the final stage of the polymerization. Potentiometric titration was carried out on the latex aqueous dispersions containing various NaCl concentrations. Conductometric titration was carried out for the salt-free aqueous dispersion. The total content of ionizable groups was determined by conductometric titration in 1,4-dioxane. The MA content in the shell, determined by potentiometric titration, is equal to that by conductometric titration. This quantity is, however, slightly smaller than that determined by back titration. We conclude that about 27% of total ionizable groups is buried in the particle interior. The potentiometric titration behavior of MA groups on the latex surface is analyzed in detail and compared to theoretical results calculated from a smeared-charge model with spherical symmetry. We determine the negative logarithm of intrinsic dissociation constant of MA at the surface, pK0= 4.8 ± 0.2, in agreement with that of low molecular weight isobutylic acid or poly(methacrylic acid). We find that the electrostatic work required to remove H+from the latex particle surface calculated from the smeared-charge model is in good agreement with the experimental results. © 1995 by Academic Press, Inc.