Background: To investigate the immunohistochemical expression profiles of mismatch repair (MMR) genes (MLH1, PMS2, MSH2, and MSH6) and explore their relationships with clinicopathological features and the expressions of P-glycoprotein (Pgp), glutathione-S-transferase (GSTπ), DNA topoisomerase II (Topo II), and cell proliferation antigen Ki-67 in patients with colorectal cancer. Methods: The clinicopathological data of 93 patients with colorectal cancer who had been treated in our hospital from February 2014 to May 2015 were retrospectively analyzed. The expressions of MMR genes (MLH1, PMS2, MSH2, and MSH6), Pgp, GSTπ, Topo II, and Ki-67 in cancer tissues were determined by immunohistochemical staining. Then we used multiple sample rate (or constituent ratio) comparisons (i.e., χ 2 test with R×C table) to analyze the relationships of the expressions of MMR genes (MLH1, PMS2, MSH2, and MSH6) with clinopathology and the expressions of Pgp, GSTπ, Topo II, and Ki-67 in colorectal cancer. Pearson correlation analyses were used to analyze the correlation of the expressions between MMR genes (MLH1, PMS2, MSH2, and MSH6) and Ki-67. Results: The missing expression rate of MMR genes MLH1, PMS2, MSH2, and MSH6 were 14.0%, 17.2%, 10.8%, and 11.8%, respectively. The expression rates of Pgp(−), Pgp (+), Pgp (++), and Pgp (+++) were 3.2%, 25.8%, and 51.6%, 19.3%. The expression rates of GSTπ (−), GSTπ (+), GSTπ (++), and GSTπ (+++) were 3.3%, 16.7%, 56.7%, and 23.3%. Topo II had no negative or level IV expression, and its level I, II and III expressions accounted for 19.3%, 77.4%, and 3.2%. The expression rates of Ki-67 50% (+) accounted for 1.3%, 25%, and 50%, respectively. The missing expressions of MMR genes (MLH1, PMS2, MSH2, and MSH6) showed no significant correlation with gender, age, histological differentiation, and TNM staging (all P>0.05). There was also no significant correlation (P>0.05) between MSH2 missing expression and the lesion location (P>0.05). However, the missing expressions of MLH1, PMS2, and MSH6 showed significant correlation with the lesion location (P 0.05). However, the missing expressions of MLH1, PMS2, MSH2, and MSH6 were significantly correlated with the Ki-67 expression (P 50% (+) were 6.1%, 4.1%, 8.2%, and 6.1%, respectively. MLH1, PMS2, MSH2, and MSH6 missing expressions were negatively correlated with Ki-67 expression (correlation coefficient r=−0.969, r=−0.464, r=−0.143, r=−0.344, respectively; all P Conclusions: The missing expressions of MMR genes (MLH1, PMS2, MSH2, MSH6) are more likely to occur in right colon, followed by left colon and rectum. The missing expressions of these MMR genes are negatively correlated with Ki-67 expression.