The present study was undertaken to examine early T lymphocyte activation in chronic hepatitis B virus (HBV) carriers. Nineteen hepatitis B surface antigen-positive patients (eight with liver cirrhosis and 11 with chronic hepatitis) and 18 healthy controls were studied in a period free of other infection. Mitogen-stimulated cellular interleukin 2 receptor expression, soluble interleukin 2 receptor release, and interleukin 2 production were studied in peripheral blood mononuclear cells cultured for 24 h. No difference was demonstrated between the patients and healthy controls in the cellular interleukin 2 receptor expression, soluble interleukin 2 receptor release, and interleukin 2 production. Pokeweed mitogen-stimulated interleukin 2 production in lymphocytes from cirrhotic patients was significantly lower than that of the noncirrhotic patients. However, the cellular and soluble interleukin 2 receptor levels did not differ between the two groups of chronic HBV carriers. Despite the fact that it has been suggested that autoreactive T cells have a role in mediating the development of chronic liver diseases associated with HBV infection, this study fails to demonstrate a defective T lymphocyte activation in these patients. The observed reduction of interleukin 2 production from activated lymphocytes may be related to the severity of liver impairment, rather than the HBV infection itself.