Objectives To establish the semi-quantitive RT-PCR method for detecting CD5 mRNA and investigate the correlation between CD5 mRNA level in B lymphocytes of peripheral blood from hepatitis B patients and persistence and severity of the disease.Methods The semi-quantitative RT-PCR method was established to detect CD5 mRNA in B lymphocytes from hepatitis B patients.The patients with acute,chronic hepatitis B and posthepatitis B cirrhosis were investigated.Results There was no significant diffcrence in CD5 mRNA level B lymphocytes between acute hepatitis B patients and the controls,while the CD5 mRNA levels in the patients with chronic hepatitis B,chronic severe hepatitis B and posthepatitis B cirrhosis were significantly higher than that of controls(P<0.01).Conclusions CD5 mRNA level in B lymphocytes of peripheral blood from hepatitis B patients is closely related with persistant process of the disease.