The liver histology of 68 consecutive anti-HCV/HCV-RNA positive chronic hepatitis patients who were HBsAg/anti-HBs negative, anti-HBc positive (Case bC group) was compared with that of 68 anti-HCV/HCV-RNA positive chronic hepatitis patients who were HBsAg/anti-HBc negative (control C group). The patients were pair-matched by age (+/-5 years), sex, and risk factors for the acquisition of parenteral infection. Case bC group showed a significantly higher mean fibrosis score (2.3 +/- 1.1) than control C group (1.5 +/- 1.1, P <0.001) and more histological evidence of cirrhosis (22% vs. 7.3%, P <0.05). In addition, the patients in Case bC group showed more severe inflammation of the portal tracts (3.5 +/- 0.8 vs. 3.0 +/- 1.1, P <0.005) and there was a higher prevalence of patients with rhomboid-shaped hepatocytes (26.4% vs. 2.7%, P <0.005), acidophilic bodies (33.8% vs. 1.4%, P <0.0001), sinusoidal inflammation (29.4% vs. 10.3%, P <0.01), lymphoid follicles in the portal tracts (72% vs. 44.1%, P <0.05), Kupffer cell proliferation (29.4% vs. 11.8%, P <0.05), bile duct damage (44.1% vs. 10.3%, P <0.0001), and ductular proliferation (30.9% vs. 2.7%, P <0.001) than in control C group. No difference in these histological features was observed between HBV-DNA negative and positive patients in Case bC group. The data suggest that anti-HBc positive patients with HCV chronic infection have a significantly higher degree of liver fibrosis, and that hepatocellular apoptosis, bile duct damage, and ductular proliferation correlate with the presence of this antibody in the serum.