Although it has been known for some time that estrogen deficiency is a major pathogenetic factor for osteoporosis related fractures among postmenopausal women, the capability of estrogen (with or without a progestin) to prevent fractures has often been questioned. The publication of the data from the two hormone clinical trials of the Women's Health Initiative lays that discussion to rest. In both studies what have been considered a standard dose of conjugated estrogen with or without medroxyprogesterone acetate significantly reduced the risk of all fractures, including clinical vertebral fractures and hip fracture, in a population of postmenopausal women, average age 63 yr, not selected for osteoporosis by BMD. These results are particularly impressive given the difficulty of finding a fracture benefit in lower risk populations with other anti-resorptive agents. Surrogate data on lower doses of hormone therapy suggest a fracture benefit would be seen if studies were to be done. The other outcomes in WHI make it important to define appropriate clinical guidelines for use of hormone therapy for prevention of fractures in postmenopausal women.