A mild one-step route was successfully established for the preparation of iron nanoparticles by reduction of iron salts with hydrazine hydrate in a strong alkaline solution. Pressure played an important role for the fabrication of a pure alpha-Fe phase. The effects of the concentration of alkali and solvents on the formation of iron were also investigated. This synthetic method proved to be very facile and easy to be scaled up. (c) 2004 Elsevier B.V. All rights reserved.