On basis of the redox reaction between MnO4- and Mn2+, a facile hydrothermal method combined with the adjustment of pH value in the reaction system has been employed to synthesize single-crystal gamma-MnOOH nanorods, and square-like Mn3O4 nanoparticles. Additionally, single-crystalline beta-MnO2 and Mn2O3 nanorods can be obtained after subsequent calcinations of the as-prepared gamma-MnOOH nanostructures at 300 degrees C and 600 degrees C, respectively. Furthermore, electrochemical property of as-obtained beta-MnO2 is also studied. (C) 2006 Elsevier Ltd. All rights reserved.