The G protein beta3 (GNB3) subunit and HLA are candidate genes predictive of immune response capacity. We therefore studied the influence of both gene systems on cellular and humoral immunity against hepatitis B virus (HBV) in 79 HBV booster-vaccinated healthy volunteers and an independent group of 77 probands after HBV basic immunization. Following booster vaccination, lymphocyte in vitro proliferation after stimulation with HBV surface antigen was 2.5-fold increased in GNB3 825T (TC + TT) vs CC allele carriers (P = 0.01) and was not influenced by HLA-DRB1 or DQB1 alleles. In addition, anti-HBs antibody titers in both groups were 2-fold increased in TC vs CC and decreased in TT vs CC allele carriers. However, antibody titers after HBV booster immunization were elevated in HLA-DQB1*0301 carriers (P corrected = 0.027). In summary, the GNB3 825T allele appears as a marker particularly predictive of cellular and HLA-DQB1*0301 of humoral immune responses following HBV vaccination.