The recurrent formation of renal calculi following the surgical removal of a stone from the kidney constitutes a major problem in the management of patients with renal lithiasis. That formation of secondary calculi will frequently occur unless adequate preventive measures are instituted seems plausible when it is obvious that, in the majority of instances, the underlying factors associated with the production of the primary calculus are not corrected or eradicated by the surgical procedure. From experimental and clinical observation, it appears evident that no one etiologic agent is entirely responsible for the formation of all kidney stones. This emphasizes the necessity for an intensive preoperative investigation to ascertain the causative factors in each individual case. This facilitates correction of these factors at the time of surgical treatment or during the postoperative regimen. Certainly the operative procedure per se constitutes but one phase in the management of this group of patients,