Zoledronic acid is a bisphosphonate that is effective in the treatment of complications of metastatic bone disease. We have carried out a perspective study on 24 consecutive patients with prostate cancer metastatic to bone to verify the effect of zoledronic acid on analgesic response and a possible relationship with the levels of bone metabolism biomarkers. Eligibility for this study required prostate cancer patients with metastatic bone disease and pain not controlled by analgesics. Patients were excluded from the study if they were receiving cytotoxic chemotherapy or radiation therapy within three months. Eighteen patients (75%) were considered responder to acid zoledronic, only 6 patients did not respond. Before starting treatment (T0) mean Visual Analogue Scale was 7.8 (SE +/- 0.29), after 1 month therapy (T1) was 3.6 (SE +/- 0.3) and after three months (T2) was 3.1 (SE +/- 0.4) with a significant difference between T0 and T1 (p<0.0005) and between T0 and T2 (p<0.0005). Visual Analogue Scale improvement was positively correlated with decrease of C-telopeptide and bone phosphatase alkaline (p<0.05) serum levels.