Background: Vascular endothelial growth factor (VEGF) is a potent angiogenic factor related to tumor growth and metastasis. However, little is known about the clinical significance of circulating VEGF in cancer patients. Patients and Methods: Eighteen patients with non-small cell lung cancer received chemotherapy using carboplatin and paclitaxel. Plasma levels of VEGF were analyzed at baseline and after 2 cycles of chemotherapy. Results: Partial remission was observed in 3 patients (16.7%), stable disease in 10 patients (55.6%) and progressive disease in 5 patients (27.8%). Patients with partial remission or stable disease had significantly lower levels of plasma VEGF than did patients with progressive disease, both at baseline (p=0.0341) and after 2 cycles of chemotherapy (p=0.0265). There were no significant changes of plasma VEGF during chemotherapy. Conclusion: Pretreatment plasma levels of VEGF are a useful marker for predicting disease control by chemotherapy.