Vitamin K treatment has been reported to prevent bone fracture (s) in osteoporosis. However, the effect of vitamin K(2) on bone could not be evaluated by the assessment of bone mineral content. Possible marker to assess the effect of Vitamin K(2) is serum total osteocalcin and/or glu-osteocalcin. These two indices were changed by the administration of Vitamin K(2). Vitamin K(2) may promote osteocalcin production and/or secretion from the bone cell.