All subjects will be treated with teriparatide (human, recombinant PTH[1-34])(human, recombinant PTH[1-34]), 20 microgram subcutaneously daily for 12 months. Subjects will consist of 290 postmenopausal women previously treated with either risedronate or alendronate for at least 24 months. An approximately equal number of subjects will have been previously treated with risedronate and alendronate, and the subjects will be balanced with regard to duration of previous treatment.