Potassium manganese oxide (K(0.27)MnO(2)center dot 0.5H(2)O) nanowires/ribbons have been synthesized successfully by a simple hydrothermal method at low temperature. The nanoribbons have rectangular sections with widths of 50-200 nm, thicknesses of 20-25nm, and lengths up to hundreds of micrometers; nanowires have diameters of 20-30nm and lengths up to hundreds of micrometers. A plausible formation mechanism of the one-dimensional nanostructure and the effect of the anion effect used for the starting reactants on the product are discussed. Temperature dependence resistivity of one nanowire follows the small polaron theory p = AT exp(E-a/k(B)T), and a small magnetoresistance was observed in the paramagnetic potassium-intercalated manganese oxides. (c) 2005 Elsevier B.V. All rights reserved.