Many risk factors that predispose to osteoporosis have been identified, but the fundamental pathogenesis remains unknown. Abnormalities in systemic calcium regulating hormones are probably less important than changes in local factors. Risk factor analysis, particularly using bone mass measurements, can provide the basis for effective prevention programs with calcium, exercise, and hormone replacement therapy. Treatment of established osteoporosis is limited. In addition to a preventive regimen, further bone loss may be prevented by fluoride therapy, which stimulates bone formation, or calcitonin, which inhibits bone resorption.