The chlor-alkali industry consumes large amounts of energy. The gas diffusion cathode has been investigated for energy saving modifications. To commercialize the process, an electrode of high durability is required. Electrolytic operating factors causing electrode deterioration were examined. Under the condition of low oxygen concentration operation, the degradation of the electrode was significantly accelerated. The life of the electrode was also estimated by an acceleration test. The relationship between the logarithm of the life and the operating overvoltage was linear. Using this relation, the life of a possible mass production electrode was assumed to be five years or more.