By studying the influences of H(2)O(2) on the catalase and peroxidase actions and metabolisms of cells belonging to Sh. dysenteri 1-7, the author obtained the following results: 1. No evidence of H(2)O(2) accumulation either by cells with catalase or those without catalase can at all be seen during the growth or glucose oxidation. 2. In the relationshp betwen the peroxidase activity and H(2)O(2) concentration, the cells possessing catalase differs from without catalase. 3. The addition of glucose even in the case of cells lacking catase will enable to dispose of H(2)O(2). 4. In the case of the cells possesing no catalase, it seems that H(2)O(2) is not a all produced in the course of the metabolism, or some H(2)O(2) is produced momentarily but such H(2)O(2) is immediately disposed of by pyruvate or other substances produced during the metabolism.