Treatment with etidronate alone is unlikely to increase the bone mineral density of the femoral neck. In combination of etidronate and hormone replacement therapy has been shown to markedly increase the bone mineral density of the femur and may decrease the risk of fracture. These findings suggest that etidronate and hormone replacement therapy inhibit bone resorption by different mechanisms of action. Treatment with a combination of etidronate and hormone replacement therapy may therefore be an important option for the management of postmenopausal osteoporosis.