With the use of the standard strains of St. aureus, albus and citreus, stocked in our laboratory, as experimental materials, the author studied the enzymatic activity, especially the modes of glucose oxidation, and obtained the following results: 1. Enzymatic activity of both bacteria is generally higher when the length of culture is short (10 hours) and the initial pH is low (5.8), and culture temperature is low (20℃). This fact seems to be depend upon phases of the growth ; namely, the enzymatic activity of cells in the log phase, especially the enzymatic activity involved in the T.C.A. cycle, appears to be great. 2. In the case of St. aureus and albus it seems that the glucose oxidation of the cells in lag phase mainly depends on the E-M pathway, while in the cells at stationary phase it develops other pathways; namely, W-D pathway, or glucose ➝ gluconate ➝ 2 ketogluconate (or 5-ketogluconate) pathwag. In contrast to this in the case of St. citreus, the glucose oxidation of cells at all phases seems to take mainly the E-M pathway.