Vascular endothelial growth factor (VEGF), a secreted endothelial-specific growth factor, and microvessel density was examined in 204 primary non-small cell lung carcinomas. The expression of VEGF was evaluated by immunohistochemical staining using an anti-VEGF antibody. Positive staining was obtained in 125 out of 204 cases (61%). Tumor vascularity was quantitatively assessed by microvessel counting after staining with the endothelial-specific marker factor VIII. The mean microvessel count for all patients was 9.6 ± 10.4. Expression of VEGF was closely associated with increment of microvessel density. Postoperative follow-up of patients demonstrated a trend that survival time of patients with VEGF-positive tumors was worse than that of patients with VEGF-negative tumors. In contrast, microvessel density was not a prognostic factor.