BACKGROUND: Osteoporosis is a common illness frequently leading to serious adverse outcomes for patients. Hip, wrist and vertebral fractures have considerable impact on both costs to healthcare system and lives of those who suffer from those events. Each year in the US, an estimated 1.5 million fractures occur due to osteoporosis [Riggs and Melton, 1995]. Estimated incremental cost of osteoporosis related events in subsequent years after fracture is US$4007 [Rousculp, 2007]. Bisphosphonates are widely used and are considered an effective intervention for risk reduction of postmenopausal fractures. OBJECTIVES: The present study was conducted to compare the cost of IV bisphosphonates used for risk reduction of post-menopause vertebral and non-vertebral fractures under the private payer perspective in Brazil. METHODS: According to local legislation, private payers are not obliged to cover oral drugs, therefore, oral forms of biphosphonates were not considered in this study. The most important IV bisphosphonates in the private market are ibandronate and zolendronate. There are no head-to-head clinical trials comparing both compounds. Both studies of ibandronate [Eisman, 2008] and zolendronate [McClung, 2007] demonstrated their non-inferiority against oral bisphosphonates. Therefore, a cost-minimization approach was taken. Drug prices were obtained from official public sources (Kairos Magazine, May 2009).  Administration costs were obtained from medical society physicians fee list (CBHPM, 2008, v.5). Since the time horizon of this analysis is one-year no discount rate was utilized. Costs are presented in Brazilian Reais (US$1.00 ~ R$2.00  in May 2009). RESULTS: Total cost per patient was R$1534.36 for ibandronate and R$1951.26 for zolendronate. Administration costs represented about 11% of total cost of ibandronate (administrated four times a year) and 2% for zolendronate (administrated once a year). CONCLUSIONS: Findings suggest that IV ibandronate is a cost-saving therapy with potential to yield 21% reduction in total cost per patient under Brazilian private payer.