Clinical trials of estrogen/progestin replacement therapy (HRT) and a bisphosphonate, alendronate (ALN), have demonstrated that both are effective in causing gains in bone mass and preventing bone loss and fractures in postmenopausal women. The FDA has approved both these drugs for prevention and treatment of fractures, and both are widely used in clinical practice. Because both are approved and effective, and they work by different mechanisms, many patients and their physicians ask whether both should be taken in combination, particularly in cases of severe disease. The question is asked frequently because of the high incidence of osteoporosis among women and the need for long-term prevention and treatments that often last decades.