Abstract： Objective To explore the expression of MRP1 and CD34 in colorectal carcinoma tissue and the relationship with clinicopathological factors.Methods Immunohistochemical streptavidin-perosidase method was used to examine the expression of MRP1 and CD34 in 53 cases with colorectal carcinoma and normal colorectal tissue.The correlation between the levels of MRP1 and CD34 expression and clinicopathological factors were analyzed.Results The positive expression rates of MRP1 in the carcinoma group and normal colorectal tissue group were 49.1％ and 15.1％ respectively,and there was a significant difference of the positive expression between the two groups( x2 =14.029,P ＜ 0.01 ).The expression of MRP1 had no correlation with the degree of differentiation,the depth of invasion,the metastasis of lymph node and all the other clinicopathological factors ( P ＞ 0.05 ).CD34 value in the carcinoma group and normal colorectal tissue group were ( 35.63 ± 12.23 ) MVD/HP and ( 6.12 ± 0.97) MVD/HP,respectively,and there was a significant difference between the two groups (t =17.565,P ＜ 0.01 ).CD34 was not correlated with age,sex,tumor size,localization of the primary tumor ( P ＞ 0.05 ),but correlated with Dukes staging,lymph node metastasis,differentiation of the tumor,depth of invasion( all P ＜ 0.05).Conclusion The overexpression of MRP1 and CD34 protein may involve in colorectal carcinogenesis;MRP1 may involve in the primary multidrug resistance in colorectal carcinoma.; CD34 may involve in the colorectal carcinoma invasion and metastasis.Investigating the expression of MRP1 and CD34 in colorectal carcinoma simultaneously can provide new referential indexes for the treatment and prognosis of colorectal carcinoma.