Interleukin 10 (IL10) is a powerful Th-2 cell cytokine produced by lymphoid cells that exerts its functions by inhibiting macrophage/monocyte and T-cell lymphocyte replication and secretion of inflammatory cytokines (IL1, TNFA, TGFB, IL6, IL8 and IL12). Genetic association analysis of a well-characterized HBV cohort revealed that one of IL10 haplotypes, IL10-ht2, was strongly associated with hepatocellular carcinoma (HCC) occurrence in gene dose-dependent manner. The frequency of susceptible IL10-ht2 was much higher in HCC patients and significantly increased in order of susceptibility to HBV progression from chronic hepatitis to liver cirrhosis and HCC among hepatitis B patients. In addition, survival analysis clearly showed that the onset age of HCC was also accelerated among chronic hepatitis B patients who were carrying IL10-ht2. Increased IL10 production mediated by IL10-ht2 suggests that up-regulated IL10 accelerates progression of chronic HBV infection, especially to HCC development.