Kidney stone formation due to an excess of calcium in the urine is a common problem. It is treated with thiazide diuretics. These drugs often cause excessively low blood potassium levels that in turn require large doses of potassium supplements. These supplements are often large, unpleasant and easy to forget. We are trying the addition of spironolactone to these patients' medications to see if it allows them to take a lower dose of potassium.