Abstract: Objective 　To study the expression of thymosin β4 in colorectal cancer and it s clinical significance. Methods 　Forty-one cases of human colorectal cancer specimens was collected f rom the patients ho received operation for colorectal cancer from 12/ 2003 to 11/ 2004. All of the specimens were determined for mRNA expression of thymosin β4 by using RT-PCR technique. Results 　Thymosin β4 mRNA was high-expressed in colorectal cancer specimens although they were also expressed in normal colorectal specimen. The result s of semi-quantitative PT-PCR analysis showed the expression of thymosin β4 mRNA was 0. 65 ±0. 21 and 0. 42 ±0. 19 in cancer and normal tissues, respectively, P < 0. 01. The relative values of mRNA in lesions with metastatic lymph nodes (0. 82 ±0. 23) was higher than those of non-metastatic lymph nodes (0. 53 ±0. 19) ( P < 0. 05) ; expression of thymosin β4 in Duke C or Duke D stage (0. 82 ±0. 22) was significantly higher than that in Duke A or Duke B stage (0. 51 ±0. 18) . There was a close relation between thymosinβ4 mRNA expression and several clinicopathological factors including ymph node metastasis, and TNM stage. Conclusion 　Thymosin β4 gene expression in colorectal cancer may serve as a parameter for judging tumor biological characteristic and clinical significance.