Background: Strontium ranelate (SR) is a new antiosteoporotic agent with antiresorptive and bone-forming properties. The exact mechanism by which SR exerts its effects is not clearly understood. Bone resorption requires interaction between osteoblasts and osteoclasts. Osteoblasts produce a ligand for receptor activator of nuclear factor-kappa B (RANK). They also secrete osteoprotegerin, a decoy protein that blocks the interaction of RANK with its ligand, thereby inhibiting the differentiation and activity of osteoclasts. SR also has been associated with osteoblast proliferation and decreased osteoblast-induced osteoclast differentiation via increased osteoprotegerin messenger RNA expression in human osteoblasts.