The association of genetic factors with hepatitis B virus (HBV) infection susceptibility, its different manifestations, and the different responses to hepatitis B antigen vaccination have been described by several authors. With regard to HLA class I molecules, association with HLA-B was especially observed. HLA-B35 and -B8 correlated with chronic active hepatitis (CAH) and with hepatitis B carriers. Correlation between HBV infection and HLA class II (loci DR and DQ) was also indicated, but results are not clear regarding the clinical pictures of the disease nor vaccination response. HLA class III (fourth complement component ? C4, third complement component ? C3, and properdin factor ? BF) are associated with various manifestations of this disease. The gammaglobulin phenotype Gm(1, 2, 3, 10, 21) was more frequent in CAH. However, in only three publications was the impact of HLA on the efficacy of interferon therapy taken into account.