ObjectiveTo investigate the clinical significance of CK20 mRNA expression in blood of patients with colorectal cancer. MethodsThe expressions of CK20 mRNA in blood of twenty healthy volunteers, ten patients with colorectal polyp and sixtyone patients with colorectal cancer were detected by RT-PCR. ResultsThe positive rate of CK20 mRNA in peripheral venous blood and portal venous blood of patients with colorectal cancer were 41.0%(25/61) and 45.9%(28/61), which was not significantly different (Pgt;0.05). The expression of CK20 mRNA in patients with colorectal cancer was associated with clinical TNM stage of tumor, local lymph node metastasis, distance metastasis, and the depth of invasion (Plt;0.05). No expression of CK20 mRNA was detected in blood of twenty healthy volunteer’s and ten patients with colorectal polyp. ConclusionCK20 is a specific marker for detecting blood micrometastasis of colorectal cancer. The expression of CK20 mRNA in blood of patients with colorectal cancer is related with TNM stage, invasion, and metastasis of colorectal cancer.