OBJECTIVES:Bisphosphonates have been shown to be effective in reducing the incidence of skeletal-related events (SREs) in patients with metastatic bone disease (MBD) originated from any type of malignancy. The purpose of this study was to evaluate the cost-effectiveness of clodronate and zoledronate in the prevention of SREs in patients with MBD METHODS:A Markov model was developed to represent a cohort of patients diagnosed with MBD. The model had four primary health states: “without SRE”, “with SRE (i.e., pathologic fracture, radiotherapy or surgery, and hypercalcemia”), “osteonecrosis” and “death”. Patients evaluated were those diagnosed with MBD, presenting any SRE and treated with clodronate or zoledronate. Transition probabilities originated from a meta-analysis previously published by our group. Time-horizon used was five years.  Cost data were obtained from national privately-administered databases. Outcomes evaluated were costs, quality-adjusted life years (QALYs), and SRE-free years. Univariate and multivariate sensibility analyses were used to determine model robustness. Costs were reported in 2007 Brazilian Reais (1R$=1.60US$) RESULTS:MBD treatment total cost in Brazil (on average, per-patient) in five years (base-case) was R$49,004 with clodronate and R$53,076 with zoledronate. For both drugs, drug cost drove the overall cost of MBD management (>90%). Clodronate and zoledronate generated (on average, per-patient) 2.00 and 1.90 QALYs (5-year time-horizon), respectively. Within the same time-horizon, clodronate and zoledronate also generated (on average, per-patient) 1.81 and 1.76 SRE free-years, respectively. When clodronate and zolendronate were contrasted for cost-effectiveness, clodronate was considered dominant. Multivariate sensitivity analysis did not show changes in original results CONCLUSIONS:Clodronate was dominant (i.e., produced higher effectiveness and lower costs) in comparison to zoledronate for preventing SREs in patients diagnosed with MBD in Brazil from the private sector perspective