An exciting new era in bone biology is a result of our greater understanding not only of the mechanisms of action of the medications we currently use for treatment of osteoporosis but also of the molecular pathways involved in normal and abnormal bone formation. In the coming years our increased understanding of these molecular pathways will result in many new medications for osteoporosis therapy. Together with the development of new drugs it will be necessary to develop better ways of assessing bone quality. Since bone has both protein (collagen type I) and mineral (hydroxyapatite) components, both of which are essential to bone strength, measurements of bone mineral content by densitometry (DXA) will provide us with only a narrow perspective on the utility of the drug under development prior to full patient fracture studies. The information gathered from basic bone research must be used for the rational development of agents that increase bone strength within a narrow physiological window.