Interpretation of bone mineral density (BMD) results in premenopausal women is particularly challenging, because the relationship between BMD and fracture risk is not the same as for postmenopausal women. Z scores rather than T scores should be used to define "low BMD" in premenopausal women. The finding of low BMD in a premenopausal woman should prompt an evaluation for secondary causes of bone loss. If a secondary cause is found, management should focus on treatment of this condition. In some cases in which the secondary cause cannot be addressed, such as glucocorticoid therapy or cancer chemotherapy, treatment with a bone-active agent to prevent bone loss should be considered. In women with no fractures and no known secondary cause, low BMD may not signify compromised bone strength. BMD is likely to remain stable in these women, and pharmacologic therapy is rarely justified. Assessment of markers of bone turnover and follow-up bone density measurements can help to identify those with an ongoing process of bone loss that may indicate a higher risk for fracture, and possible need for pharmacologic intervention.