AIM:To compare the difference of expression of Bcl-2 andBax in extrahepatic biliary tract carcinoma and dysplasia,andto analyze the role of Bcl-2 and Bax proteins in the progressionfrom dysplasia to carcinoma and to evaluate the correlationof Bcl-2/Bax protein expression with the biological behaviors,METHODS:Expressions of Bcl-2 and Bax were examinedimmunohistochemically in 27 cases of extrahepatic biliarytract carcinomas (bile duct carcinoma:n=21,carcinoma ofampulla of Vater:n=6),and 10 cases of atypical dysplasia.Five cases of normal biliary epithelial tissues were used ascontrols.A semiquantitative scoring system was used toassess the Bcl-2 and Bax reactivity.RESULTS:The expression of Bcl-2 was observed in 10 out of27 (37.0 %) invasive carcinomas,1 out of 10 dysplasias,noneout of 5 normal epithelial tissues.Bax expression rate was74.1% (20/27) in invasive carcinoma,30 % (3/10) in dysplasia,and 40 % (2/5) in normal biliary epithelium.Bcl-2 and Baxactivities were more intense in carcinoma than in dysplasia,with no significant difference in Bcl-2 expression (P=0.110),and significant difference in Bax expression (P=0.038).Levelof Bax expression was higher in invasive carcinoma than indysplasia and normal tissue (P=0.012).Bcl-2 expression wascorrelated to Bax expression (P=0.0059).However,Bcl-2/Bax expression had no correlation with histological subtype,grade of differentiation,or level of invasion.CONCLUSION:Increased Bcl-2/Bax expression fromdysplasia to invasive tumors supports the view that this isthe usual route for the development of extrahepatic biliarytract carcinoma.Bcl-2/Bax may be involved,at least in part,in the apoptotic activity in extrahepatic biliary carcinoma. AIM: To compare the difference of expression of Bcl-2 andBax in extrahepatic biliary tract carcinoma and dysplasia, andto analyze the role of Bcl-2 and Bax proteins in the progressionfrom dysplasia to carcinoma and to evaluate the correlationof Bcl-2 / Bax protein expression with the biological behaviors, METHODS: Expressions of Bcl-2 and Bax were examined in immunohistochemically in 27 cases of extrahepatic biliary tract carcinomas (bile duct carcinoma: n = 21, carcinoma of ampulla of Vater: n = 6), and 10 cases of atypical dysplasia. cases of normal biliary epithelial tissues were used as controls. A semiquantitative scoring system was used to assess the Bcl-2 and Bax reactivity. RESULTS: The expression of Bcl-2 was observed in 10 out of 27 (37.0%) of invasive carcinomas, 1 out of 10 dysplasias, noneout of 5 normal epithelial tissues. Bax expression rate was74.1% (20/27) in invasive carcinoma, 30% (3/10) in dysplasia, and 40% (2/5) in normal biliary epithelium.Bcl- 2 and Baxactivities were more intense in carci noma than in dysplasia, with no significant difference in Bcl-2 expression (P = 0.110), and significant difference in Bax expression (P = 0.038) .Levelof Bax expression was higher in invasive carcinoma than indysplasia and normal tissue Bcl-2 / Bax expression had no correlation with histological subtype, grade of differentiation, or level of invasion. CONCLUSION: Increased Bcl-2 / Bax expression from dysplasia to invasive tumors supports the view that this the that that the usual route for the development of extrahepatic biliary tract carcinoma. Bcl-2 / Bax may be involved, at least in part, in the apoptotic activity in extrahepatic biliary carcinoma.