Electrochemical oxidation of water-insoluble amines (n-octylamine and n-decylamine) was successfully accomplished in aqueous electrolytes using acoustic emulsification. Acoustically prepared emulsions of fumaric acid diethyl ester in aqueous electrolytes can be also electro-reduced very smoothly. Ultrasonication to the water-insoluble organic substrate/aqueous electrolyte mixtures allowed a formation of very stable emulsions having the characteristic of giving narrow monomer droplet size distributions in the submicrometer range in aqueous electrolytes without added surfactants, and the smooth electrochemical reaction in the emulsions took place via direct electron transfer between the electrode and the water-insoluble organic droplets. In this kind of electron-transfer system, supporting electrolyte should be dissolved not only in the aqueous phase but also in die organic droplets and should contribute to the formation of an electric bilayer inside the droplets.