With the use of intact cells aerated 10 hours and cell-free extracts of virulent and avirulent strains of both human and bovine tubercle bacilli, the oxygen consumption has been examined comparatively, adding each of the following substrates; sugars, organic acids and amino acids. The results are as follows: 1) Even after 10 hours aeration, in both of the human and bovine tubercle bacilli (including BCG), high endogenous oxygen consumption is observed, but when made into the cell-free extracts the rate of oxygen consumption of these bacteria decreases to 1/10 to 1/20 of that of the intact cells, thus making it quite easy to study the enzymic activities of bacteria to various substrates. 2) Sugars have very little influence on the oxygen consumption. 3) As for the influence of pyruvate on the oxygen consumption, it is makedly greater in H37Rv strain than H37Ra strain; but no significant difference can be seen between bovine 263 strain and BCG. 4) In the virulent strain, lactate increases the oxygen consumption markedly greater than in avirulent strain. 5) Although citrate increases the oxygen consnmption of BCG, it has no effect on that of other strains. 6) Amino acids have little accelerating effect on the oxygen consumption of bacteria except alnine which shows some effect in the case of H37Ra strain.