Magnetic polystyrene nanospheres were efficiently prepared by using a new indirect process based on miniemulsion polymerization of styrene. The samples were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and vibrating-sample magnetometry (VSM), respectively. The experimental results clearly show that the 3-methacryloxypropyltrimethoxy silane was anchored onto the surface of the magnetic particles to form the vinyl end. The size of the magnetic particle is about 6-30 nm. The size of the magnetic particle capped with polystyrene is about 1-2 mu m. The magnetic polystyrene spheres exhibit multidomain character, whereas the pure magnetic particles show single domain character. (c) 2006 Wiley Periodicals, Inc.