Objectives To evaluate the relationship between the expression of B7-1 in liver tissue and the effect of interferon- alpha(α- IFN) treatment in patients with chronic hepatitis B(CHB).Methods The expression of B7 -1in liver biopsy specimens from 68 CHB patients was studied with immunohistochemistry before α-IFN treatment.Results B7-1 was expressed in 45(66.2%) liver tissues among 68 patients with CHB,but none in 5 normal controls.The total response ratio of α- IFN in patients with B7-1 positive was 66.7%(30/45),which was significantly higherthan 39.1%(9/23)in the patients with B7-1 negative(x2 =7.20,P <0.01).B7-1 expression was closely corelat-ed with the histological activity grade(HAI) and serum alanine transaminase(ALT) level.Conclusions The level of B7-1 expression in liver tissue may be regarded as an effective parameter for predicting α-IFN response in patients with CHB.