An attemt was made to observe the influence of phosphorus metabolism on the kidney function through clinical and experimental works.(1) ATP gave a rise of the renal clearance, especially dominant of PAH clearance, in the normal rabbits kidney.(2) We observed the effect of ATP, vitamin B1 and co-carboxylase on PSP test in kidney diseases. ATP improved PSP in the group suffering moderately, but not in the group seriously disturbed. When the kidney function was within normal limits, there were almost the same numbers of improved and constant rate of PSP excretion by ATP. Co-carboxylase effected on the improvement of PSP better than vitamin B1, and these effects were almost similar to that of ATP.(3) Inorganic phosphorus and Δ10P were measured for 120 min. after ATP administration to rats which were treated by potassium chromate leading to slightly or seriously disturbed kidney. In serious cases was noted low inorganic phosphorus, whereas Δ10P showed the highest rate in mild cases, but did not increase so much or did a slow return to the beginning rate in serious cases.(4) Blood pyruvic acid and α-ketoglutaric acid in the kidney disease showed a rise suggesting the disturbance of their utility. ATP, vitamin B1 and co-carboxylase made an improvement of these rates, especially vitamin B1 and co-carboxylase did a remarkable influence. However there was no definite difference of the effect between vitamin B1 and co-carboxylase.(5) The improvement of the kidney function by the activation of the glucose metabolism by ATP or co-carboxylase was most marked in moderately advanced kidney diseases. PSP test was revealed to indicate without any difficulty the reaction ability to the metabolism of the renal vessels and the tubules. Phosphate bound substances were suggested to play an important role in improving the kidney function by producing high energy phosphate bound substances, activation of phosphorilation as well as causing the smooth TCA cycle.