OBJECTIVES: Cost-effectiveness (C/E) studies of oral vs iv regimens are important, with the availability of oral regimens having ‘iv efficacy’, and some iv regimens being available as generics. C/E of oral ibandronate (ibandronic acid) versus iv zoledronic acid or iv generic pamidronate was assessed in breast cancer patients with metastatic bone disease undergoing iv chemotherapy. METHODS: The model assumed a UK NHS perspective, 14.3 months expected average survival, concurrent iv chemotherapy lasting 4 months, and specified probabilities for bisphosphonate discontinuation. Primary outcomes were direct healthcare costs and QALYs. Resource use for iv bisphosphonates was obtained from a published micro-costing study (validated by UK clinician); the cost of managing skeletal-related events (SREs) came from published literature. Other costs were calculated using a unit cost database. Monthly drug costs were £195 for oral ibandronate and iv zoledronic acid, and £165 for iv generic pamidronate. Renal AEs with monitoring and treatment costs were assumed for zoledonic acid. Efficacy was assessed as the relative risk reduction (RR) of SREs (assuming SRE duration of 1 month). Utilities were applied to time with/without SRE, to adjust survival for patient QOL. RESULTS: Projected total cost (including drug) was £478 less/patient for oral ibandronate than for zoledronic acid, and £1,629 less/patient than for generic pamidronate. Due to SRE RR and pain relief, oral ibandronate gained 0.02 QALYs, making it the economically dominant option versus zoledronic acid or generic pamidronate. For completeness, C/E results for iv ibandronate will also be presented, demonstrating C/E. CONCLUSIONS: Oral ibandronate was highly cost-effective compared with either iv zoledronic acid or generic pamidronate. The efficacy of oral ibandronate in preventing SREs and sustaining relief from metastatic bone pain is likely to lead to QALY gains, with cost savings due to reduced healthcare staff time for treatment of SREs, bisphosphonate administration, and patient monitoring.