Over a period spanning six months, 69 patients with lithiasis were selected for evaluation of mineral metabolism. Hypercalciuria, particularly renal, was the metabolic disorder that was commonly detected. A high incidence of altered uric acid metabolism was also observed. The importance of correct diagnosis and treatment of hyperparathyroidism is underscored because of the extraordinary benefit afforded to these patients. Correct patient selection has resulted in a lower incidence of those with normal metabolic parameters and has thus maximized the usefulness of these studies.