This experiment was conducted with the object of finding out the instinct of smooth-rough type variation, a form of bacterial variation. A comparison was made using organisms S. typhi 57-S, and 57-R, which was isolated from it. The method of experiment was mainly with Warburg manometer to measure O(2) uptake and CO(2) evaluation when various substrates were used with bacteria developed on agar platte medium and semi-synthetic medium. Furthermore, the influence of inhibiter on them was examined to arrive at the difference of metabolism of the both types from the experimental results. The results were as follows: 1. The difference of metabolism of S-type and R-type bacteria is an analysis of glucose which was found to be active until it became pyruvic acid. 2. S-type bacterium analyzes mainly by glucose and Embden-Meyerhof pathway. 3. R-type bacterium, in addition to glucose analysis and Embden-Meyerhof pathway, analyzes by glucose dehydrogenase system and Warburg-Dickens pathway. 4. It is concluded from the foregoing that if S-type bacterium changes to R-type bacterim, aerobic metaboliem system will develop.