Objective:To investigate the expression of MRP1/CD9 as well as their correlations with the metastasis of colorectal carcinoma. Methods:Tissue microarray and immunohistochemistry were used to detect the expression of MRP1/CD9 in 244 cases of colorectal carcinoma. Results:The positive rate of MRP1/CD9 expression was 77.9% in colorectal carcinoma. The expression of MRP1/CD9 had no relationship with the patients’ sex,age,and the depth of infiltration,but it had relationships with the differentiated degree,Dukes stages,and lymphnode metastasis. The expression of MRP1/CD9 was higher in colorectal carcinomas with moderate or high differention than that in the ones with poor differention. The expression of MRP1/CD9 was higher in colorectal carcinomas with Dukes A+B stages than that in the ones with Dukes C+D stages. The expression of MRP1/CD9 was higher in colorectal carcinomas without lymphnode metastasis than that in the ones with lymphnode metastasis. Above all had the significant meaning(P < 0.05). Forward stepwise binary logistic regression reveals:differentiation,which went into the equation first,is the significant factor of MRP1/CD9 expression. The expression of MRP1/CD9 was negatively related to Dukes stages in monofactoral analysis,but disappearing in multifactoral analysis. Conclusion:The loss expression of MRP1/CD9 are closed correlated with the metastasis of colorectal carcinoma,and this marker has hopes to become a new target to evaluate the tumor prognosis.