I have made a study on the renal function in 63 cases of renal calculus by examining fluid test, indigocarmin and phenolsulfonphthalein excretion test and obtained the following results: (1) Concerning the fluid test, there were 26 cases (41%) with renal dysfunction of various grades which includes 10 cases (16%) of insufficiency both in excretion and concentration abilities, 14 cases (22%) of insufficiency only in concentration ability, 2 cases (3%) of insufficiency only in excretion ability. (2) Classifying the results of the fluid test in three types according to the relationship between the urine excretion quantity and the specific gravity, 79% belonged to type I (or complete type), 13% to type III (or incomplete type), 8% to type II (or prolonged type). (3) Insufficiency of the excretion ability were found in 15% of unilateral cases and in 29% of bilateral cases, and 22% of unilateral and 82% of bilateral cases had insufficiency of the concentration ability, and so it could be said that the renal dysfunction in renalcalculus appears more frequently in bilateral rather than in unilateral cases and in concentration rather than in excretion ability. (4) In indigocarmin excretion test, concerning the unilateral cases, 12% of them showed nornal excretion from both kidneys, 57% with disturbance in the affected side, 7% in the opposite side and 24% in both sides; and in the bilateral cases, 7% of them showed normal excretion from both kidneys, 57% with disturbance in only one kidney, and 36% in both kidneys. (5) In phenolsulfonphthalein test, 17% showed excretion insufficiency, including 8% in unilateral and 40% in bilateral cases, and the bilateral cases were affected more frequently than the unilateral cases. (6) Influence of the complication of hydronephrosis to the renal function was not to be seen in the previous three tests.