Electrodeposition of amorphous Fe2O3 films of nanometer size was performed by reduction of Fe(ClO4)(3) or Fe(ClO4)(2) in oxygenated acetonitrile. Cyclic voltammetry has shown that the oxide-film formation occurs via oxidation of electrodeposited metal by dissolved oxygen. The oxide films were characterized by cyclic voltammetry, electrochemical quartz crystal microbalance, X-ray diffraction, and UV-visible spectroscopy. The films are reversibly reduced in acetonitrile + LiClO4 in two redox processes to the Fe3O4 and FeO oxides via lithium intercalation. The UV-visible (UV-vis) spectrum displays absorption with an optical gap (1.75 eV) characteristic of amorphous Fe2O3. Spectroelectrochemistry has shown that reduction causes bleaching of the yellowish films (electrochromic efficiency congruent to 30 C-1 cm(2) at 400 nm). Heating the films at 500 degrees C converts them to the crystalline alpha-Fe2O3 form with loss of electroactivity.