Vascular endothelial growth factor expression in untreated osteosarcoma is predictive of pulmonary metastasis and poor prognosis. To investigate the clinical significance of vascular endothelial growth factor (VEGF) in osteosarcoma, we immunohistochemically stained biopsy specimens of 27 primary osteosarcomas using an antibody against VEGF and evaluated the correlation between the expression of VEGF and local density of CD34-positive microvessels, clinicopathological variables, and survival of patients. VEGF staining was positive in 17 tumors (63.0%) in which the density of CD34-positive microvessels was significantly higher than that in VEGF-negative 10 tumors (P < 0.05). In terms of clinicopathological variables, there was no correlation between the expression of VEGF and histological subtype, stage, or response to neoadjuvant chemotherapy, or, strikingly, to the development of pulmonary metastasis (89% of VEGF-positive tumors versus 10% of VEGF-negative tumors; P < 0.0003). Moreover, patients with a VEGF-positive tumor were poorer in both disease-free survival (P < 0.001) and overall survival (P < 0.03) compared to those with a VEGF-negative tumor. These findings strongly suggest that VEGF expression in untreated osteosarcoma is predictive of pulmonary metastasis and poor prognosis in patients who underwent aggressive therapy and also provide the basis for a therapeutic strategy targeting angiogeneic property of osteosarcoma.