Hexagon shaped h-MoO3 nancrods have been fabricated via the probe sonication route using ammonium molybdate, urea and sodium dodecyl sulphate at 70 degrees C. Pure metastable h-MoO3 and alpha-MoO3 were obtained under the current synthetic conditions. The h-MoO3 phase was transformed to alpha-MoO3 phase at 400 degrees C, while the hexagon shape rods structures of h-MoO3 were collapsed and transformed to elongated particles of alpha-MoO3. As-prepared products were characterized by thermogravimetric analysis (TG), X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and high-resolution transmission electron microscopy (HR-TEM). (C) 2008 Elsevier B.V. All rights reserved.