Coronary-artery calcification was present in 14 of 16 hemodialysis patients who were 20 to 30 years old by electron-beam computed tomography. Bone matrix protein, such as osteopontin produced by infiltrating macrophages into the atherosclerotic arterial lesions, is thought to be associated with vascular calcification. Therefore, it is required to recognize the interaction between abnormal bone metabolism and vascular calcification. Control of serum phosphorus levels is likely to be most important for the prevention and treatment of vascular calcification in patients with end-stage renal diseases.