This 3 arm study will evaluate renal safety after administration of an intravenous (iv) injection or infusion of Bonviva, compared to oral alendronate, in patients with postmenopausal osteoporosis, at increased risk of renal disease. Patients will be randomized to receive Bonviva 3mg intravenous (iv) by a) injection or b) infusion once every 3 months, or alendronate 70mg per oral (po) weekly. The anticipated time on study treatment is 3-12 months, and the target sample size is 500+ individuals.