A Nd:YAG pulsed laser was used to ablate a 0.5-mm-diameter iron wire in a sealed chamber in a mixed gas flux of N-2 and O-2 to generate pure gamma-Fe2O3 nanoparticles at atmospheric pressure. Structural characteristics and sizes of the prepared nanoparticles were determined by X-ray diffraction and TEM. The effects of laser power density, total mixed gas pressure and the oxygen ratio on the mean particle size were investigated, respectively. The results showed that the mean particle size decreased with the increase of the laser power density, total gas pressure and the oxygen ratio, respectively. Besides, the nanoparticle formation mechanism by laser ablation of iron wires was also discussed. (c) 2005 Elsevier B.V. All rights reserved.