In the PICS 44 postmenopausal women between the ages of 55 to 75 years of age with osteoporosis who meet the inclusion/exclusion criteria,will be randomized to the following 2 treatment groups. Group A will received 6 months of monthly Ibandronate, plus daily PTH 1-84,100 μg; followed by 18 months of Ibandronate only. Group B will received 3 months of daily PTH 1-84,100 μg; followed by 9 months of monthly Ibandronate, over 2 years. Calcium (400-650 mg) and Vitamin D (400 IU) supplements will be provided to all participants.