High-quality gamma-MnO2 single-crystalline nanobelts have been synthesized by hydrothermal treatment of commercial gamma-MnO2 in NaOH aqueous solution. The products are characterized by X-ray diffractometer, scanning electron microscopy, and transmission electron microscopy. The width, thickness and lengths of gamma-MnO2 nanobelts are in the range of 80-100 nm, 10-20 nm, and several tens of micrometers, respectively. The influences of the reaction time, temperature, and medium on the morphologies of the resulting products have been investigated. (C) 2006 Elsevier B.V. All rights reserved.