Kidney stones are common, and most of them are of the calcium oxalate type. Metabolic evaluation ranging from extensive to cursory has been recommended by different experts; however, some evaluation does seem warranted, even if only a single stone has occurred. Crystallographic analysis of the stone, if recovered, and measurement of urinary excretion of calcium and uric acid are indicated. Blood chemistries, measurement of urine pH, and measurement of urinary constituents besides calcium and uric acid are probably indicated as well, but controversy exists as to whether classification of hypercalciuria is necessary for management of most patients. Most, but not all, of the literature supports the use of thiazides to prevent calcium oxalate stones and the use of allopurinol in those calcium stone formers who have hyperuricosuria. In fact, allopurinol appears to be useful in patients with calcium stones even if no metabolic abnormality is discovered.