We have reported data showing that both agents have an anabolic effect on bone in humans, meaning that they cause an increase in bone mass beyond that explained by a remodeling transient brought about by reduction in bone remodeling rates. Further, research has shown that HRT and ALN affect bone by different mechanisms. Thus, this combination may have an additive effect on bone resulting in bone gain beyond that previously seen with other interventions. This project will provide much-needed information to physicians and their patients on the benefits and safety of this combination regimen so that they can make "evidence-based" decisions on the choice of interventions to prevent and treat osteoporosis.