Synthesis of porous molybdenum dioxide MoO2 with one-dimensional (1D) and spherical morphology in aqueous solutions has been investigated systematically by varying the precursors and the reducing agents as well as the reaction temperature and durations. The average diameter of the MoO2 nanofibers is about 80-225 nm, and the length is up to 2 mu m. The average diameter of the MoO2 nanospheres is about 260-500 nm. The reduction of precursor yields a metastable amorphous oxide of lower-valence molybdenum, which will crystallize around 400 degrees C after calcinations. It has been found that the 1D morphology of the trioxide precursor and the hydrogen bonds associated with organic acid play a decisive role in determining the size and shape of the final product. The current method provides an approach to fabricate porous structure from a shaped template through redox etching process at ambient temperatures. (c) 2006 Elsevier B.V. All rights reserved.