For frequent stone formers, and even for some first-time stone formers interested in preventing future episodes of renal colic, a metabolic evaluation is necessary. The urologist, rather than members of other medical specialties, seems to have the primary responsibility of the medical management of stone disease. Thus, it is essential for the urologist to have a good working knowledge of the principles of metabolic evaluation and kidney stone prevention. This article provides guidelines related to metabolic evaluation and the prevention of kidney stones.