"Osteoporosis has been reported in anorexia nervosa (AN), but not in other eating disorders. Thirty-three patients, 8 AN, 17 bulimia nervosa (BN), and 8 eating disorder not otherwise specified (EDNOS), were evaluated by bone densitometry (radius, spine, femur) to determine the prevalence and distribution of osteoporosis and the role of physical parameters, exercise and estrogen. All three diagnostic subgroups had evidence of decreased bone density, worst in the EDNOS subgroup and least in the BN subgroup. The most affected site was the femur, least the spine; the radius was intermediate. Age, body surface area, age of onset, and length of illness weakly correlated with the femur and spine density in the BN and EDNOS subgroups. Exercise was related to bone density in the AN subgroup in the femur, moderate exercise having a protective effect and strenuous exercise being detrimental. No significant correlation of bone density measurements with estradiol levels and/or history of amenorrhea was identified. Eating disorder patients are at risk for osteoporosis, which has multiple contributing factors including physical parameters and exercise. Estrogen deficiency by itself may not be a major causative factor."