BACKGROUND: Anorexia nervosa is highly prevalent among young women. OBJECTIVE: To determine prevalence and predictive factors for regional bone loss. DESIGN: Prospective cohort analysis. SETTING: University hospital. PATIENTS: 130 women with anorexia nervosa. MEASUREMENTS: Dual-energy x-ray absorptiometry. RESULTS: The prevalence of osteopenia (-1.0 SD >/= T-score > -2.5 SD) and osteoporosis (T-score </= -2.5 SD) was 50% and 13% for the anterior-posterior spine, 57% and 24% for the lateral spine, and 47% and 16% for the total hip, respectively. Bone mineral density (BMD) was reduced by at least 1.0 SD at one or more skeletal sites in 92% of patients and by at least 2.5 SD in 38% of patients. Weight was the most consistent predictor of BMD at all skeletal sites. Twenty-three percent of patients were current estrogen users, and 58% were previous estrogen users. Bone mineral density did not differ by history of estrogen use at any site. CONCLUSIONS: Bone mineral density is reduced at several skeletal sites in most women with anorexia nervosa. Weight, but not estrogen use, is a significant predictor of BMD in this population at all skeletal sites.