Painful skeletal metastases are a common site of advanced disease. For instance, in breast cancer, and despite cancer treatments (radiotherapy, cytotoxic treatment and adequate treatment of pain), the patients often need additional treatments that may relieve their symptoms. Bisphosphonates, such as ibandronic acid, have in pilot studies shown a significant decrease in pain scores, both after loading dose and after long-term treatment. In this study the safety and efficacy of an intravenous loading dose of three times 6 mg ibandronate during three consecutive days in breast cancer patients with painful skeletal metastases will be studied.