In vertebrates, the development and integrity of the skeleton requires hydroxyapatite (HA) deposition by osteoblasts. HA deposition is also a marker of, or a participant in, processes as diverse as cancer and atherosclerosis. At present, sites of osteoblastic activity can only be imaged in vivo using γ-emitting radioisotopes. The scan times required are long and the resultant radioscintigraphic images suffer from relatively low resolution. We have synthesized a near-infrared (NIR) fluorescent bisphosphonate derivative that exhibits rapid and specific binding to HA in vitro and in vivo. We demonstrate NIR light–based detection of osteoblastic activity in the living animal and discuss how this technology can be used to study skeletal development, osteoblastic metastasis, coronary atherosclerosis and other human diseases.