Alpha-, beta-, gamma-, and delta-MnO(2) single-crystal nanowires/nanorods with different aspect ratios have been successfully prepared by a common hydrothermal method based on the redox reactions of MnO(4)(-) and/or Mn(2+). The influences of oxidant, temperature, and inorganic cation (NH(4)(+) and K(+)) template concentrations on the morphology and crystallographic forms of the final products are discussed in this paper. It is interesting to find that all the MnO(2) one-dimensional nanostructures have a similar formation process: delta-MnO(2), which has a layer structure, serves as an important intermediate to other forms of MnO(2), and is believed to be responsible for the initial formation of MnO(2) one-dimensional nanostructures. A rolling mechanism has been proposed based on the results of the series of TEM images and XRD patterns of the intermediate.