Monodisperse aqueous latex dispersions, prepared from mixtures of styrene, N-isopropylacrylamide, and N,N '-methylenebisacrylamide, were characterized. Thermosensitive composite microspheres with diameters greater than 1.0 mu m, consisting of a polystyrene core and a poly(N-isopropylacrylamide) shell, were prepared. The morphology of the composite rnicrospheres was observed with transmission electron rnicroscopy, and the particle size of the composite microspheres was estimated with dynamic light scattering. The thermosensitive properties of the composite microspheres were evaluated via the hydrodynamic size of the composite microspheres. The particle size of the composite microspheres decreased with increasing temperature. (c) 2005 Wiley Periodicals, Inc.