OBJECTIVES: Oral ibandronate (ibandronic acid) is a bisphosphonate approved in the UK for treatment of bone metastases from breast cancer. Administration of oral ibandronate once-daily can be easily combined with oral hormonal therapy, saving costs of iv bisphosphonate administration and monitoring. We used cost-effectiveness (C/E) modelling to compare oral ibandronate with iv zoledronic acid or iv generic pamidronate in this setting. METHODS: The model assumed a UK NHS perspective with a duration of 14.3 months (expected average survival). Patients were assumed to receive oral hormonal therapy for 53% of their survival. Primary outcomes were direct healthcare costs and QALYs. Resource use data for iv bisphosphonates came from a published micro-costing study (validated through review by a UK clinician); costs were calculated using a unit cost database. Monthly drug acquisition costs were £195 for oral ibandronate and iv zoledronic acid, and £165 for iv generic pamidronate. The cost of managing skeletal-related events (SREs) came from a published study. Renal adverse events with monitoring and treatment costs were assumed for zoledonic acid. Efficacy was calculated as the relative risk reduction (RR) of SREs; utility scores were applied to time with/without an SRE (SRE duration assumed 1 month). RESULTS: The projected total cost was £386 less/patient with oral ibandronate than with zoledronic acid, and £1,697 less than with generic pamidronate. Oral ibandronate led to a gain of 0.02 QALYs (due to SRE RR and bone pain relief), making it the economically dominant treatment option. For completeness, C/E results for iv ibandronate will also be presented, demonstrating C/E. CONCLUSIONS: This study demonstrated the use of C/E modelling to compare oral versus iv bisphosphonates using published data validated by expert clinician review. Oral ibandronate was found to be cost-effective for the management of bone metastases from breast cancer in patients receiving oral hormonal therapy.