OBJECTIVES: Breast cancer often metastasizes to the bone, which leads to poor quality of life for the patients. Many patients with bone metastases are currently treated with bisphosphonates. There are different molecules and formulations of bisphosphonates available. Intravenous (IV) administration is associated with more resource utilization and higher cost than oral administration due to use of hospital facilities, equipments and increased pharmacy and nurse time for preparing and administrating the drug. The objective of this study was to estimate resource use and perform a microcosting analysis of bisphosphonate administration in the treatment of metastatic bone disease in Swedish breast cancer patients. METHODS: A sample of patients receiving IV administration of bisphosphonate was identified at two hospitals in Stockholm and Uppsala, Sweden. All patients had breast cancer with bone metastasis. Resources associated with IV administration were identified and the utilization estimated. The resource use attributable to the bisphosphonate administration during each patient visit was recorded in a data collection form specifically developed for the study. RESULTS: The 26 patients included in the study all received either ibandronate or zoledronic acid. The cost analysis showed that the mean cost of bisphosphonate administration to breast cancer patients was €94. Of this, 84% constituted direct costs and 16% indirect costs. The patients spent on average 76 minutes at the clinic and the administration took on average 16 minutes. Nursing time and cost of facilities were the greatest direct cost drivers. CONCLUSION: The patients included in the study all received bisphosphonates requiring short infusion times. The administration is associated with costs, which should be taken into account in the choice of bisphosphonate treatment. Bisphosphonates requiring longer infusion time than the drugs included in this study would be associated with higher costs. The incremental cost per additional infusion hour was estimate to about €33.