In recent years, bone quality is thought to be an important factor in bone strength. Vitamin K(2) (VK(2))drugs inhibit bone fracture, although their effect of increasing bone mineral density (BMD)is lower compared to bisphosphonate. This suggests VK(2) analogs improve bone quality. Glucocorticoid-induced osteoporosis(GIOP)brings about a bone fracture even under the condition of high BMD. VK(2) drugs might be effective to prevent bone fracture in GIOP, because they increase bone strength independently of bone mineral density (BMD).