The number of patients with high blood pressure and osteoporosis are increased year by year in our society. In hypertension patients, excess urinary calcium secretion induces secondary parathyroidism to increase serum calcium level by calcium release from bone, which may accelerate osteoporosis. In this aspect, there are several reports that anti-hypertensive drugs, especially thiazides, increase bone mineral density and decrease the incidence of bone fracture. In addition, we demonstrated that renin-angiotensin system can be involved in the process of osteoporosis. Angiotensin II significantly induced the expression of RANKL (receptor activator of NF-κB ligand) in osteoblasts, leading to the activation of osteoclasts, while these effects were completely blocked by an Ang II type 1 receptor blockade. Recently, it has been reported that angiotensin receptor blockade clinically decreased the incidence of bone fracture. Renin-angiotensin system might be common molecule to regulate both hypertension and osteoporosis.