In a consideration of conservative operations on the kidney, I have grouped the cases into (1) those in which there is obstruction usually due to stone in the ureter, pelvis of the kidney, or the calices; (2) those in which obstruction similarly situated, not the result of calculi, produces hydronephrosis, and (3) those in which a diseased portion of a duplicated kidney exists. On a previous occasion, I presented the results following conservative operations in the latter two groups; namely, successful resection of the renal pelvis and removal of the infected hydronephrotic portion of a duplicated kidney. I shall therefore refer to these groups briefly. After the passage of another year I still believe firmly that, if sufficient renal parenchyma remains, such kidneys can be preserved. HYDRONEPHROSIS In June, 1930, I reexamined a patient whose right renal pelvis had been resected eighteen months previously for hydronephrosis and whose left renal