beta-FeOOH nanorods with the diameter of only 10 nm were fabricated through a facile PEG-assisted hydrothermal synthetic route, which was the smallest dimension reported for the fabrication of beta-FeOOH one-dimensional (1-D) nanostructures so far. The as-prepared ultrafine beta-FeOOH nanorods were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and galvanostatic tests. Electrochemical tests on the as-obtained ultrafine beta-FeOOH nanorods revealed that they exhibited excellent electrochemical properties with a large discharge capacity of 290 mA h g(-1) and good cycleability, which enabled them to be applied as superior cathode materials for lithium ion battery systems.