Background: The aim in this study was to determine if an association of excision repair cross-complementing group 1 (ERCC1) gene and mismatch repair (MMR) status with overall survival (OS) could be found from our analysis of a large cohort of Chinese colorectal cancer patients (CRC). Methods: In total, 2,233 tissue samples isolated from individual CRC tumors were assessed by immunohistochemistry for the expression of ERCC1 and 4 MMR genes. Results: The rates of proficient MMR (pMMR) and ERCC1 expression were 89.6 and 90.7%, respectively. We found that patients with positive ERCC1 expression and deficient (d) MMR status had higher overall survival (OS) than those with either positive ERCC1 and pMMR, negative ERCC1 and dMMR, or negative ERCC1 expression and pMMR status (OS 79 vs. 69 vs. 66 vs. 61%, hazard ratio (HR) 0.90, 95% confidence interval (CI) 0.80-1.00; p = 0.043). Despite this finding, we found no statistical difference in OS between ERCC1-positive and -negative CRC patients when ERCC1 expression was considered alone (OS 70 vs. 62%, HR 0.82, 95% CI 0.65-1.04; p = 0.11). Conclusion: Our results indicate that the combined examination of ERCC1 expression and dMMR status can be used to aid OS assessment in CRC patients. (C) 2017 S. Karger GmbH, Freiburg