Antimony doped tin oxide (ATO) nanoparticles were prepared by coprecipitation reaction in methanol solution of tin(IV) chloride pentahydrate and antimony(III) chloride. The obtained ATO nanoparticles did not form any secondary particles and showed loosely agglomerated structure consisting of primary particles weakly attached with each other by van der Waals and capillary adhesive forces. In addition, ATO nanoparticles showed lower degree of agglomeration compared with those of commercial product. The reason for the formation of weakly agglomerated structure was discussed. (c) 2005 Elsevier B.V. All rights reserved.