Abstract: A process for the production of amorphous, crystalline, or mixed oxides of metals having mean particle diameters of 1 to 500 nm, by providing an electrolysis cell having a cathode in a cathode half-cell and an anode in an anode half cell, providing in the electrolysis cell a solution comprising ions of a metal or metals from which the oxide particles are to be formed dissolved in an organic electrolyte, and electrochemically reducing the metal ions at the cathode in the presence of an oxidizing agent while impeding or preventing passage of halogens from the anode half cell to the cathode half cell, to form the oxide or oxides.