Abstract: Objective :To study the correlation between the serum level of endostatin and the ex-pression of CollagenⅩⅧ/Endostatin mRNA in lung cancer tissues and to explore the relationship be-tween these levels and the clinical and pathophysiological characteristics in non- small cell lung cancer(NSCLC) patients. Methods :The serum level of endostatin was detected in 46 patients with NSCLCusing ELISA and the expression level of CollagenⅩⅧ/ Endostatin mRNA was detected in the lung can-cer tissues by RT-PCR. Results :a)The mean serum concentration of endostatin in the lung cancerpatients was 20.85±.56ng/ml and the expression level of CollagenⅩⅧ/Endostatin mRNA in the lungcancer tissues was 0.872±071.b) The serum concentration of endostatin and the transcription expres-sion of CollagenⅩⅧ/Endostatin mRNA were closely related to the P- TNM stages, presence of distantmetastasis, grade of cell differentiation and the size of the primary tumor (P<0.05), but not to the histo-logical classification, type of tumor, lymph node status, age, sex of the patients or cigarette use (P>0.05).c) The serum level of endostatin in lung cancer patients had a highly positive correlation to theexpression of CollagenⅩⅧ/Endostatin mRNA in lung cancer tissues (r=0.686, P<0.01). Conclusion :The serum level of endostatin in lung cancer patients has a highly positive correlation to the expressionof CollagenⅩⅧ/Endostatin mRNA in lung cancer tissues.The serum level of endostatin and the ex-pression of CollagenⅩⅧ/Endostatin mRNA in patients with NSCLC might be helpful for evaluating thebiological behavior of lung cancer.