Kidney stones are a major cause of morbidity. The lifetime prevalence of symptomatic nephrolithiasis is approximately 10% in men and 5% in women,1-3 and more than $2 billion is spent on treatment each year.4,5 About 80% of kidney stones contain calcium, and the majority of calcium stones consist primarily of calcium oxalate.6,7 The identification of common, modifiable risk factors for kidney stones may result in new approaches to treatment and prevention.