Abstract: Objective: To study the relationship between p53 gene mutation and the protein expression,and their roles in the early diagnosis and clinical significances in colorectal cancer.Methods: Using polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP),the mutations in exon 58 of p53 gene were examined in the tumor tissues and stool of 34 patients and 10 healthy controls.At the same time,using immunohistochemistry(IHC)(S-Pmethods),p53 protein expression were examined in the tumor tissues and normal mucosa.Results: The mutation of exon 58 and protein expression of p53 gene in the tissues were found in 18 of 34(52.9%) cases and 19 of 34(55.9%) cases,respectively,no mutation and protein expression were positive in normal mucosa(P<0.01).Of 12 patients who were positive for p53 gene mutation in tumor tissue,5(41.7%) had evidence of alterations in the p53 gene within the stool.The positive rates of p53 protein expression was correlates with the mutation of exon 58.The expression of p53 protein was correlated with tumor size(P<0.05),but not correlates to other cliniopathological factors.Conclusions: Our data indicate that gene mutation of p53 is one of the main factors which participate and affect the protein expression.p53 gene mutation can be detected within the stools.Detection of p53 gene in stool may provide new ways for the early diagnosis and census of high risk population in colorectal cancers.