Background: To determine the clinical significance of KRAS mutation and ERCC1 overexpression as a predictive factor of resistance in oxaliplatin based treatment. Methods: We retrospectively analyzed the clinicopathologic features, status of KRAS mutation and ERCC1 overexpression of 386 colorectal cancer patients who received curative intent surgery. Among them 84 patients were treated by FOLFOX regimen as the first line. Their disease-free survival and overall survival according to the KRAS and ERCC1 were analyzed. Results: About a quarter of patients (25.5%) were represented KRAS wild type with ERCC1 overexpression. Among the patients who treated by FOLFOX regimen, 73 patients were evaluated both of the KRAS and ERCC1. There were no significant differences of disease-free survival and overall survival according to KRAS status and ERCC1 expression each. Under the subgroup analysis, overall survival of ERCC1 overexpression group in wild type KRAS was poor than ERCC1 negative group (p=.029), but no significant difference was in mutant KRAS group (p=.671). Conclusions: Our results suggest that the KRAS wild type with ERCC1 overexpression would be associated with the resistance of oxaliplatin.If oxaliplatin based chemotherapy would beconsidered, status of KRAS mutation and ERCC1 overexpression should be evaluated.