Several bisphosphonates appear to be effective for preventing bone loss associated with estrogen deficiency, glucocorticoid treatment, and immobilization and for partially reversing bone loss in patients with postmenopausal osteoporosis and steroid-induced osteoporosis. The most promising of these agents are etidronate, alendronate, tiludronate, and risedronate. These agents should have an important role in prevention and treatment of osteoporosis; however, more research is needed regarding optimal doses and regimens (continuous versus intermittent), comparisons with other agents, and use in combination with other agents.