Using immunohistological methods, we studied the lymphoid follicles in liver biopsy specimens obtained from patients with chronic hepatitis C(CH-C) to determine whether they represented an autoimmune manifestation. In 84 specimens obtained by liver biopsy from 76 patients positive for C-100 antibody, we assessed the presence or absence of lymphoid follicles within the portal areas, and then compared the clinical and immunohistological profiles of the two groups defined on this basis. There were no significant differences in the serological and clinical profiles of the two groups, but the T4:T8 cell ratio within the portal areas differed significantly. A T4:T8 cell ratio > 1.0 was more common in the specimens containing lymphoid follicles. This finding resembled the distribution of T cell subpopulations in the portal areas of patients with autoimmune hepatitis, and suggested that lymphoid follicles may be worth investigating to elucidate the relationship between chronic hepatitis C and autoimmune hepatitis.