Liver biopsies from 27 patients were studied by the indirect immunofluorescence and immunoperoxidase technique for relative distribution of B cells and T-cell subpopulations. T-cell subsets were defined for OKT4(+) (helper/inducer) and OKT8(+) (suppressor/cytotoxic) cells by using mouse hybridoma monoclonal antibodies. Patients with chronic active hepatitis and those with primary biliary cirrhosis showed marked relative increments in suppressor/cytotoxic OKT8(+) lymphocytes within hepatic lymphocytic infiltrates. Other patients with acute hepatitis or those with only reactive changes also showed a relative increment in OKT8(+) T lymphocytes within hepatic biopsy material. These findings suggest that tissue lymphocytic subpopulation increments in suppressor/cytotoxic T-cell subpopulations are commonly associated with hepatic lymphocytic infiltrates and may be related to disorders of immune regulation or expression in some of these disorders.