alpha-MnO2 nanowires were obtained by reflux treatment of precursor delta-MnO2 in acidic medium under ambient pressure. The great effects of pH on the transformation of delta-MnO2 to alpha-MnO2 and the concentration of coexistent cations (K+, Mn2+) was investigated in systematically designed experiments by using powder X-ray diffraction and atomic absorption spectrometry analysis. The specific surface area of the products could be simply controlled by adjusting the initial pH value of the suspension. The micromorphologies during the transition process from the precursors to final products were characterized by SEM and TEM. A dissolution-recrystallization mechanism was proposed to describe the growth process of the one-dimensional nanowire. MnOx units or MnO6 octahedra was formed firstly from the dissolution of outmost surfaces of delta-MnO2, followed by a rearrangement/crystallization to form one-dimensional alpha-MnO2 nanowire. In addition, the time-dependent process of dissolution would take place gradually from the external to internal of the precursor. (C) 2010 Elsevier B.V. All rights reserved.