Ten patients who have had multiple kidney stones primarily due to hypercalciuria and who are currently on stable dose of thiazide or thiazide plus amiloride will be enrolled in the study. In addition, pts have to require at least 60mEq of K supplementation a day or be on 40mEq and be hypokalemic and unable to tolerate increased K supplements. We will then give them 50mg a day of spironolactone for four weeks. A complete 24-hour urine stone profile will be obtained before and after the drug is administered. After four weeks the patients' serum potassium will be rechecked, and their dose will be lowered according to a nomogram.