[en] The rate of oxidative dissolution of uranium dioxide with ferricyanide ions was measured by the potentiostatically controlled coulometry. The rate and the total amount of the reaction were influenced by many factors including the concentration of ferricyanide, the kind and the concentration of supporting electrolytes, pH and temperature. The main product of the reaction was uranyl ions which formed the complexes competitively with ferrocyanide ions and with the anions of the supporting electrolytes. When the rate of the formation of uranyl ferrocyanide is predominant, an insoluble film produced on the surface of uranium dioxide inhibits further dissolution. Jander's equation was applicable to the initial rate of the reaction; and this fact suggests that the reaction proceeds predominantly by the film formation even in the initial stage. The film formation may be prevented by adoption of other supporting electrolytes which can form a soluble complex of high stability constant with uranyl ions. (auth.)