To elucidate the clinical courses of children chronically infected with HB virus (HBV), RIA values of anti-HBc were surveyed in 88 cases with positive HBs antigen. Among 56 children with positive HBe antigen, 20 had negative, indefinite or low titers of anti-HBc, and 18 (90%) of them had no liver malfunction. Out of 30 cases with abnormal liver function tests, 28 (93%) had high titers of anti-HBc. Follow-up study for a period of over 12 months reveals that serum HBe antigen disappeared in 10 out of the 40 cases who were positive for this antigen. All of the 10 cases had liver malfunction and high levels of anti-HBc. Among 12 children with initially positive anti-HBe, five had high titers of anti-HBc. Out of 13 children who once had high levels of anti-HBc, 3 showed reduction in titers of anti-HBc during the follow-up period in accordance with decrease in activity of hepatitis. Four out of 16 who initially had HBe antigen and low titers of anti-HBc showed high titers of anti-HBc during the observation period, while only one of 33 who had HBeAg and a high titer of anti-HBc went to the low titer group of anti-HBc, though continuously positive for HBe antigen. We presume that high levels of anti-HBc indicate previous or current liver damage due to HBV infection, while low titers of anti-HBc indicate that HBV-derived liver damage has not yet occurred or that a long time has passed since the last episode of liver damage subsided.