This 2 arm study will investigate the efficacy and safety of Bonviva (150mg po monthly) in the prevention of glucocorticoid-induced osteoporosis in post-menopausal women. Patients will be randomized to receive either Bonviva 150mg po or placebo monthly, with vitamin D and calcium supplementation. The anticipated time on study treatment is 1-2 years, and the target sample size is 100-500 individuals.