Osteopenia is a frequent and severe complication of anorexia nervosa. Once established, it is difficult to treat and is only partially reversible. Osteoporosis is a preventable disease, and intervention should begin during childhood and adolescence. Optimizing peak bone mass accrual during adolescence is essential, and an episode of anorexia nervosa during adolescence interferes with that process. In anorexia nervosa, results with hormone replacement therapy have been disappointing. Calcium and vitamin D supplementation should be prescribed where necessary. Excessive exercise should be avoided and moderate weight-bearing exercise encouraged. Ongoing research studying newer modalities such as IGF-1, DHEA, and bisphosphonates looks promising. Until more effective treatment regimens become available, the mainstay of treatment remains weight gain, nutritional rehabilitation, and spontaneous resumption of menses.