Patients with metastatic bone disease often have severe bone pain and debilitating skeletal complications. Zoledronic acid is the only bisphosphonate shown to be safe and effective in reducing skeletal-related events (SREs), including pathological fractures, spinal cord compression, and radiation or surgery to bone in patients with bone metastases from advanced prostate cancer or renal cell carcinoma (RCC). In both tumour types, zoledronic acid significantly decreased the overall risk of developing an SRE, delayed their onset and significantly reduced the incidence of SREs compared with placebo. In patients with RCC, zoledronic acid also significantly delayed the time to progression of bone lesions by 5 months compared with placebo. Zoledronic acid is safe and well tolerated with long-term use.