Objective: The aim of this study was to investigate the MRP-1/CD9mRNA expression in lung cancer and normal lung tissues and the relationship between its expression and pathologic grades, clinical stages, metastasis and prognosis.Methods: To observe MRP-1/C9mRNA expression, tissue microarray (TMA) containing 54 lung cancers and 10 normal lung tissues was prepared and Fluorescence in situ hybridization was used. Results: The positive rate of MRP-1/CD9 expression was 48.1% in lung cancer, lower than that of normal lung tissues. The statistical difference was significant (P＜0.05). Its protein expression had no relationship with the patients ages, sex and the macroscopic type of tumor, but had relationships with the histological type, clinical stage, differentiated degree and metastasis. The expression in non-small cell lung cancer (NSCLC) was higher than that in small cell lung cancer (SCLC); in well-moderately differentiated group was higher than that in poorly differentiated group; Earlier period group (Ⅰ+Ⅱ) was higher than in later period group (Ⅲ+Ⅳ); and in group without lymphoid metastasis was higher than in patients with lymphoid metastasis. Conclusion: The progression of the lung cancer maybe related with the descended MRP-1/Cd9 expression, which may be useful in evaluating the prognosis of cancer patients.