To understand better the complex natural course of HBV infection, the expression patterns of HBcAg and HBsAg in the liver of 51 inactive serum HBsAg carriers (24 CPH and 27 NPD) were studied by immunohistochemical methods. The inactive serum HBsAg carriers were devided into 3 groups by the following expression patterns of serum HBeAg/anti-HBe status and tissue HBcAg and HBsAg. Pattern A (18 cases) : HBeAg+, cHBcAg+ (94.4%), mHBsAg+ (61.1%), pATTERN B (14 cases) : anti-HBe+, nHBcAg+, cHBsAg+, Pattern C (19 cases) : anti-HBe+, HBcAg-, cHBsAg+ (89.5%). There were no significant differences between CPH and NPD, lthough the core free pattern was more common in the latter. The cHBcAg was expressed in 17 of 18 (94.4%) HBeAg seropositive cases but only one of 33 cases with serum anti-HBe, suggesting that the cHBcAg is intimately related to HBeAg. Since the inactive HBsAg carriers also expressed cHBcAg and/or mHBsAg, the necro-inflammatory activity of HBV infected liver is assumed to depend on the host immune response rather than their presence alone