Diminutive kidney, hypoplasia or atrophic pyelonephritis, may be the cause of hypertension, lumbar or abdominal pain, obscure gastrointestinal symptoms or chronic urinary infection accompanied by chills and fever. A hypoplastic kidney is prone to infection and stone formation.Diagnosis includes meticulous x-ray examination and renal function studies employing the more accurate quantitative phenolsulfonphthalein test of each kidney. Nephrectomy is the treatment for unilateral disease causing symptoms; localized atrophic pyelonephritis is amenable to partial resection. Since urinary stasis invites infection, obstructing ureteral strictures should be dilated. Pyelectasis, secondary to ptosis, and ureteropelvic obstruction should be corrected by nephropexy or plastic repair. These conservative measures may prevent renal destruction.SIXTEEN PATIENTS WERE SUBJECTED TO NEPHRECTOMY: Six because of persistent pain and chronic infection and ten because of hypertension. The six with pain and chronic urinary infection were relieved. In six of the ten with hypertension, the disease recurred within six months to seven years.