The composition of the mononuclear cell infiltrate in the liver was studied in patients with autoimmune and hepatitis B virus (HBV)-induced liver disease. The ratio of inducer to cytotoxic/ suppressor cells was greater in patients with lupoid chronic active liver disease, primary biliary cirrhosis, and HBeAb positive HBV-induced chronic active liver disease than in patients with HBeAg positive HBV-induced chronic hepatitis. In patients with chronic HBV-induced (HBeAb positive) liver disease, this ratio was greater in the periportal/portal area than in the lobule. These data are consistent with a relative deficiency of the cytotoxic/suppressor population of T cells in autoimmune liver diseases and possibly in HBeAb positive HBV-induced chronic active liver disease. In the latter patients, different ratios in the periportal and centrilobular zones suggest different mechanisms for periportal and lobular hepatitis.