In this study we have investigated changes in circulating angiogenic factors after a single zoledronic acid intravenous infusion. Thirty consecutive patients who had histologically confirmed breast (n = 20) and lung cancer (n = 10) associated with confirmation of bone metastases were included in the study. Serum was also available from 10 healthy volunteers. Four mg of Zoledronic acid (Zometa, Novartis) was administered as a 15-min infusion in 100-ml normal saline on an outpatient basis. Venous blood for assessment of serum parameters was drawn just before the beginning of drug infusion and again at 7 and 28 days after the zoledronic acid infusion. Serum levels of VEGF and bFGF were assayed with ELISA kits. Serum VEGF and bFGF levels were not significantly different from healthy control groups (P > 0.05). However, we found that serum VEGF levels in lung cancer patients were significantly higher than in patients with breast cancer and controls (P = 0.009, and P = 0.022, respectively). We found no significant correlation between serum VEGF and bFGF levels. No statistically significant changes were seen following infusion of zoledronic acid in patients with bone metastases for both serum VEGF and bFGF levels (P > 0.05). Unlike previous studies, zoledronic acid did not appear to exert an angiogenic activity as there was no reduction of VEGF and bFGF circulating levels after zoledronic acid infusion.