Fe3O4 microoctahedrons have been synthesized through a hydrothermal reduction approach using K-3[Fe(CN)(6)] complex as a single precursor. The X-ray diffraction (XRD) pattern indicates that the as-synthesized Fe3O4 microoctahedrons are well crystallized. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images show that the final product consists of larger numbers of microoctahedrons with the size ranging from 1.2 to 4 mu m. Selected-area electron diffraction (SAED) and high-resolution transmission electron microscopy (HRTEM) images prove that the Fe3O4 microoctahedrons are single crystals. The effect of reductant, NaOH concentration, temperature, reaction time on the morphologies of the final product has been investigated, and a possible solid-solution-solid growth mechanism is suggested to explain the formation of Fe3O4 micro octahedrons. The magnetic properties of the structure show relatively high saturation magnetization (112.7 emu/g) and coercivity (102.8 Oe) detected by a vibrating sample magnetometer. (C) 2007 Published by Elsevier B.V.