Background: The genetic factors of colon cancer play an important role in the tumor development and growth. The incidence of colon cancers has greatly increased in China. However, few data is available for the relationship between human muth homolog 1 (hMLH1) gene mutation at site 415 and sporadic colon cancers in Chinese population. Objective: Investigate the relationship between G→C mutation in hMLH1 gene at site 415 and sporadic colon cancers in Chinese Han population. Methods: Using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and DNA sequencing techniques, the genotype of the hMLH1 gene was analyzed at site 415 in 97 cases of sporadic colon cancer patients and 138 controls. Reverse-transcription (RT)-PCR was used to determine the level of hMLH1 mRNA expression in normal colonic mucosa of patients with different genotype. Results: The frequency of genotype C/C at the 415 site of the hMLH1 gene was significantly higher in colon cancer patients than in controls. The expression levels of hMLH1 mRNA in normal colonic mucosa were similar in colon cancer patients with different genotypes. Conclusion: G’!C mutation in hMLH1 gene at site 415 may represent a genetic factor that is associated with sporadic colon cancer in a small group of Chinese Han population.