Using the New Yoshida Tumor, the author investigated the energy metabolism by observing the inhibition of the respiration and the inorganic phosphorus intake of the calls by NaF, 2, 4-dinitrophenol (DNP), and aureomycin (AM). The following results were obtained. 1) By the addition of glucose into the reaction media, the respiration, the respiration of the tumor cells was inhibited to some extent compared to the control, though the inorganic phosphorus intake of that was retained almost same as the control. Whereas the addition of Mg into the media did not show remarkable effects on the respiration and on the phosphorus intake. 2) When glucose was not added into the media, the respiration was markedly inhibited by NaF in dilution of 10(-1)M, but was rather accelerated by that in dilutions of 10(-2) and 10(-3)M: the phosphorus intake was also inhibited by NaF in diluticn of 10(-1)M, and conversely accelerated by that to slight extent in dilutions of 10(-2) and 10(-3)M. However, as the addition of glucose into the media, it was also inhibited by NaF in dilution of 10(-1)M; and conversely accelerated, by that to slight extent in dilution of 10(-2) and 10(-3)M. However, as the addition of glucose into the media, it was noticed that the respiration was inhibited by NaF in any dilutions and that the phosphorus intake was accelerated, especially in dilution of 10(-2)M. 3) The endogeneous respiration and the phosphorus intake of the tumor cells were inhibited by DNP in any dilutions, 10(-3), 10(-4), and 10(-5)M. The inhibitions of these were reduced as the addition of glucose into the media, respectively, especially on the phosphorus intake. 4) AM did not show inhibitory effect so remarkably on the phosphorus intake irrespective of the additicn of glucose; but showed considerable inhibition on the endogenous repiration in dilutions of 10(-3) and 10(-4)M. The inhibited endogenous respiration was not recovered by the addition of glucose in contrast with the inhibition by DNP. 5) The O(2) uptake and the phosphorus intake were also studied on the cells suspended, in 0.85% NaCl, ascitic supernatant, and amniotic fluid of chick embryo, respectively, in all reaction media glucose was added as substrate. And both accelerations of the respiration and of the phosphorus intake were remarkable in order of 0.85% NaCl, amniotic fluid and ascitic supernatant. The inhibitory effects on the O(2) uptake and the phosphorus intke by NaF, DNP, and AM were regarded to be similar to each other in respective cell suspensions mentioned above.