Abstract: BACKGROUND ＆ AIM： To investigate the role of Bcl-2，Bcl-xL and Bax protein in colorectal carcinomatous tumorigenesis by detecting their expression in cancerous and adjacent tissues(>5cm from the cancerous tissue). MATERIALS AND METHODS： The expression of Bcl-2，Bcl-xL and Bax protein by S-P staining were detected in 39 colorectal cancerous tissues and adjacent tissues. RESULTS：The expression of Bcl-2 protein were often absent or weak，and no significant difference between cancerous tissue and adjacent tissue was found(Z=0.072,P>0.05).On the contrary，the immunostaining intensity of Bcl-xL protein was higher and stronger in cancerous tissues than adjacent tissues(Z=3.157,P<0.05), The immunostaining intensity of Bax protein was the strongest，but showed no significant difference between cancerous and adjacent tissues(Z=1.707,P>0.05). Only the expression of Bcl-2 protein demonstrated a negative correlation with Dukes and TNM stages(rs=－0.389,－0.396,P<0.05), all others had no relationship with clinicopathological parameters(P>0.05). CONCLUSION： Bcl-2 gene might play an important role in the early stage of colorectal carcinomas，however, Bcl-xL gene might be more important in the later stage. On the other hand, Bcl-2 protein expression may correlate with prognosis.

Key words: colorectal carcinomas, Bcl-2, Bcl-xL, Bax, immunohistochemistry, apoptosis