Osteoporosis is characterized by low-energy fractures resulting from inadequate bone mass and compromised microarchicture. Bone mass is maximized by adequate nutrition and calcium intake, normal menstrual cycles, and appropriate exercises. Low bone density, as determined by dual-energy x-ray absorptiometry, and high bone turnover, as characterized by elevated bone collagen breakdown products, are the primary indicators of bone fragility. Prevention and treatment of osteoporosis should emphasize adequate calcium and vitamin D intake and exercise. In addition, estrogen supplementation and selective estrogen receptor modulators (estrogen antagonists) can enhance bone mass and decrease the risk of spinal fractures, oral and intravenous bisphosphonates can significantly decrease the incidence of both spinal and hip fractures, and antiosteoporotic agents can help rebuild healthy bone.