Patients with breast carcinoma often develop bone metastases that carry a high risk of complications. A randomized, placebo-controlled trial was conducted to evaluate the efficacy and safety of ibandronate in patients with metastatic bone disease following breast cancer. The primary efficacy end point of the study was the proportion of patients who developed skeletal-related events (SREs, defined as pathologic fracture, spinal cord compression, radiation therapy to bone, change in anti-neoplastic therapy and surgery to bone). Secondary end points included time to first skeletal event, skeletal morbidity rate (events/year) and time to progression of bone lesions. In 150 patients (148 [female symbol] / 2 [male symbol]) with breast carcinoma and bone metastases, treatment with intravenous ibandronate 6 mg over 15 min every 4 weeks for 24 months significantly reduced the proportion of patients who experienced an SRE compared with placebo (36% vs. 48%; P = 0.027). Time to first SRE was also delayed significantly (median 457 vs. 304 days; P = 0.007). Multiple event analysis showed that ibandronate reduced the risk of developing an SRE by 32% (hazard ratio = 0.69; 95% confidence interval 0.42-0.79; P = 0.003). In general, ibandronate was well tolerated with very rare grade 3 or 4 toxicity. In this study, ibandronate was shown to be significantly more effective than placebo as a treatment for metastatic bone disease from breast cancer using multiple end points.