Polyaniline/nano-CeO2 composite microspheres with an average diameter of 7 mu m have been synthesized in a toluene/water emulsion solely stabilized by CeO2 nanoparticles (Pickering emulsion). Various experimental techniques were employed to characterize the polyaniline/nano-CeO2 composite microspheres. The microspheres are flaky polyaniline/nano-CeO2 composite particles; in the microspheres, polyaniline was amorphous while the CeO2 nanoparticles maintained their cubic crystal structure; CeO2 nanoparticles were partly enwrapped by polyaniline. A mechanism for the formation of the polyaniline/nano-CeO2 composite microspheres was proposed. (c) 2005 Elsevier B.V. All rights reserved.