Serum osteocalcin, also called bone gla protein, is one of sensitive and specific markers for metabolic bone diseases.Current evidence suggests that the protein may be involved in the regulation of calcium homeostasis in bone.We measured serum osteocalsin levels by radioimmunoassay in 100 patients with urolothiasis, especially in calcium containing stone formers and evaluated the influence of bone metabolism on the formation of calcium-containing stones.Although serum osteocalcin levels in most patients were normal, those of two male and four female patients were high.We considered that they were patients with renal hypercalciuria and secondary hyperparathyroidism and in them the formation of calcium containing stones were influenced by disorder of bone metabolism. In addition, we suggest that serum osteocalcin levels may be available index for the effect of treatment in stone formers with renal hypercalciuria and bone disease.