A microparticulated, organic-inorganic hybrid system, useful as an active agent carrier, was successfully developed with an emulsification/solvent evaporation method. The system consisted of nanostructured polystyrene microparticles containing different silicates as nanosized fillers and benzophenone (BP) as a model active substance. The adopted preparation procedure gave high yields of microparticles, which displayed regular geometry and high encapsulation efficiency of the active agent. X-ray diffraction measurements showed that all of the hybrid systems had a polymer silicate intercalated morphology and the BP was molecularly dispersed in the microspheres. Moreover, preliminary in vitro release tests evidenced that the inclusion of the nanodispersed silicates into the polymer matrix significantly modified the release behavior of BP, depending on the silicate type. Therefore, the nanocomposite microparticles are of great potential in the field of controlled release. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 122: 3694-3700, 2011