Dual-responsive micrometer-sized core-shell composite polymer particles were prepared by dispersion polymerization followed by seeded copolymerization. Polystyrene (PS) particles prepared by dispersion polymerization were used as core particles. N-isopropyl acrylamide (NIPAM) and methacrylic acid (MAA) were used to induce dual-responsive that is thermo- and pH-responsive properties in the shell layer of composite polymer particles, prepared by seeded copolymerization with PS core particles. Temperature- and pH-dependent adsorption behaviors of some macromolecules on composite polymer particles indicate that produced composite polymer particles exhibit dual-responsive surface properties. Copyright (c) 2007 John Wiley & Sons, Ltd.