Monodispersed CdS-SiO2 core-shell particles ranging from nanometers (30-100 nm) to micrometers (1.5-2 mum) were prepared in situ in the nonionic reverse microemulsions. After treating the core-shell particles with concentric nitric acid, the hollow silica spheres were obtained correspondingly. The particles were characterized by transmission electron microscope (TEM), selected area electron diffraction (SAED), scanning electron microscope (SEM), X-ray fluroscence (XRF), X-ray powder diffraction (XRD), nitrogen (N-2) physiadsorption, etc. The study shows that the core size and shell thickness could be tuned simply by controlling the addition amount of the reactants and the addition way; that through further processing (e.g. grafting other functional molecules on the particle surface), advanced materials could be prepared; and that the hollow silica spheres could be potentially used as a novel class of catalyst supports. (C) 2004 Elsevier B.V. All rights reserved.