We have conducted a study of composite polymer particles with a gradated resin composition by suspension polymerization, in which the resin composition gradually changes from the surface to the center of the particles. The binder resin of the polymer particles consists primarily of styrene, butyl acrylate, and methacrylic acid (MAA). Fourier transform infrared/photoacoustic spectroscopy analysis of the polymer particles by suspension polymerization has proved that MAA, having a higher polarity, concentrates near the surface of the particles, and this results in a formation similar to a core-shell structure. These composite polymer particles are excellent in blocking resistivity because the resin, containing a higher concentration of MAA, has a high glass-transition temperature. Composite polymer particles with a gradated MAA concentration could be used for toner applications in low-power hot-roll fusing electrophotography systems because the melting property of the core resin is controlled and allows fusing at lower temperatures. (c) 2005 Wiley Periodicals, Inc.