Single-crystal line alpha-Mn2O3 nanorods with diameters 60-130 nm and lengths ranging 0.7-2.5 mum, as well as single-crystalline Mn3O4 particles, have been prepared through a simple and facile preparation method of ammonia-hydrothermal treatment of commercial granular/bulky MnO2, which involves no catalysts or templates and is capable for large-scale preparation. (C) 2004 Elsevier B.V. All rights reserved.