Three monoclonal anti-T-cell antibodies, specifically directed against total T cells (OKT3), inducer-helper T cells (OKT4) and suppressor/cytotoxic T cells (OKT8), were used in this study to analyze peripheral T-cell subsets in hepatitis B surface antigen (HBsAg)-positive and -negative chronic active hepatitis (CAH) patients. Results showed that a clear-cut difference exists in the distribution of peripheral T cells of these two groups of subjects. HBsAg-positive CAH patients had a numerical predominance of peripheral T lymphocytes expressing the characteristics of cytotoxic/suppressor T cells. In contrast, patients with "autoimmune" HBsAg-negative CAH exhibit a predominance of OKT4 cells, namely, the helper-inducer T-cell subset. In addition, high numbers of circulating double labeled cells (expressing both the OKT4 and the OKT8 xenoantigens) were detected in some of the HBsAg-positive and HBsAg-negative CAH patients studied.