Bone is the most common location of metastatic disease. Approximately 80% of all bone metastases are observed in patients with breast or prostate tumours and are responsible for more than 300 000 deaths every year. Treatment of malignant bone disease with bisphosphonates has been shown to reduce bone events and delay their onset, and several reviews and meta-analyses have confirmed the benefit of these drugs in controlling bone metastases. Zoledronic acid is a bisphosphonate that has been shown to delay or prevent the development of skeletal-related events in patients with bone metastases. Furthermore, compared with other bisphosphonates, zoledronic acid has also shown better pain control and various studies also suggest an improvement in quality of life, although with no impact on overall survival. The duration and optimal regimen for long-term zoledronic acid therapy have not yet been defined, but some studies suggest that continuing zoledronic acid therapy for more than 2 years could also extend its beneficial effect.