Starlike and flowerlike Fe3O4 nanoparticles were synthesized by the pyrolysis method using 1-adamantanecarboxylic acid (ACA) and oleylamine (OLA), ACA and 1-adamantaneamine (AA) as the combined surfactants, respectively. XRD, TEM, HRTEM, PPMS are used to characterize the structure and magnetic property of the as-synthesized nanostructures. Control over the morphology of these nanoparticles was realized by using different surfactants under otherwise similar reaction conditions. (c) 2006 Elsevier B.V. All rights reserved.