Postmenopausal osteoporosis is preventable and treatable. Women need not lose bone mineral density (BMD) after the menopause. Without intervention, all women lose bone after menopause, regardless of the amount of calcium, vitamin D, and exercise they undertake. Postmenopausal women need estrogen replacement, a selective estrogen receptor modulator (SERM), or a bisphosphonate to prevent bone loss. Alendronate, risedronate (bisphosphonates) and raloxifene (SERM) are approved for the prevention of bone loss. The diagnosis of at-risk postmenopausal women can best be accomplished by measuring BMD in all postmenopausal women age 65 years and older regardless of their risk profile and in all postmenopausal women under 65 years with one or more risk factors. Treatment guidelines direct physicians to treat postmenopausal women with T-scores lower than -2.0 SD regardless of their risk profile and postmenopausal women with T-scores lower than -1.5 SD with one or more risk factors. The lower the BMD, the greater the fracture risk, particularly in individuals with increased age, existing fragility fractures, or high bone turnover. The best intervention for a patient should be individually selected, based on careful clinical assessment. Although calcitonin is not approved for prevention, it is approved for treatment. The labeling of estrogens has been modified to state that they may be used to "manage" osteoporosis. The lack of efficacy of calcitonin to prevent bone loss during the first 5 years after menopause, and the lack of prospective fracture reduction data for estrogen, have resulted in these labeling restrictions. Alendronate, risedronate, and raloxifene are currently approved for the treatment of osteoporosis. Both of these compounds have been shown to increase BMD and decrease fracture risk. Monitoring of a patient's response to treatment may be accomplished using serial BMD testing and biomarkers of bone turnover.