A recent editorial inThe Journal,1inspired by the published results of experimental work on repair hydronephrosis,2emphasized the potential ability of renal tissue to undergo repair. Admittedly, the future advance of renal surgery largely depends on the surgical appreciation of this fact. Conservation of renal tissue must ever be the chief objective. Nephrectomy, except for such conditions as tuberculosis, malignant disease and acute fulminating infections, must be the procedure of last resort, even though it is often the safest and simplest. No theory of counterbalance of two kidneys can replace this principle in practice. Success or failure in any condition, with such exceptions as just mentioned, depends on the efficiency or inefficiency of the surgeon in removing the primary and secondary causes of injury, and radical removal by nephrectomy is often the worst failure of all in the surgical treatment of many purely unilateral diseases, particularly hydronephrosis.