The well-defined superparamagnetic Fe3O4@polystyrene@polyaniline (Fe3O4@PS@PANi) sandwich microspheres or yolk/shell Fe3O4@ polyaniline (Fe3O4@PANi) hollow microspheres were prepared via the facile chemical oxidative polymerization of aniline with the Fe3O4@polystyrene (Fe3O4@PS) core/shell nanoparticles as the "partially sacrificial templates". When the templates were prepared with different amount of initiator added, holes with different sizes appeared in the final magnetic composite microspheres. The possible mechanism of the formation of the different morphologies has been proposed. According to transmission electron microscopy (TEM), the diameter of the Fe3O4@PS@PANi sandwich microspheres and the yolk/shell Fe3O4@PANi hollow microspheres is about 230 nm and the shell thickness is about 40 nm, respectively. (C) 2012 Elsevier B.V. All rights reserved.