A phase transformation induced by the reduction of as-synthesized gamma-maghemite (gamma-Fe2O3) nanoparticles was performed in solution by exploiting the reservoir of reduction gas (CO) generated from the incomplete combustion reaction of organic substances in the reactor. Results from X-ray diffraction, Color indicator, and magnetic analysis using a SQUID strongly support this phase transformation. Based on this route, monodisperse magnetite (Fe3O4) nanoparticles were simply produced in the range from 260 to 300 degrees C. Almost all aspects of the original gamma-Fe2O3 nanoparticles, such as shape, size, and monodispersity. were maintained in the produced Fe3O4 nanoparticles. (C) 2009 Elsevier Inc. All rights reserved.