Background : Green Cross HG-II vaccine is recombinant hepatitis B vaccine derived from yeast Hansenula polymorpha. Its immunogenicity and safety using 0-1-6 months vaccination schedule were proven. This prospective study is conducted to evaluate immunogenicity and safety of HG-II according to 0-1-2 months schedule. Methods : 20 g of HG-II vaccine was given intramuscularly at 0, 1, and 2 months to 118 healthy adults seronegative for hepatitis B markers. Sera were assessed for anti-HBs by radioimmunoassay at 1 months and 7-10 months after completion of vaccination. Results : 113 of 118 (95.8%) completed vaccination schedules. The seroconversion rate at 1 month after completion of vaccination was 93.8% (106/113) and protective titers of anti-HBs developed in 82.3% (93/113). The geometric mean titer (GMT) of anti-HBs was 64.91 mIU/ml in all seroconverted vaccinee. There was no incapacitating serious side effect associated with vaccinations. The seropositive rate at 7-10 months after vaccination was 95.3% (81/85) with protective rate of 84.7% (72/85). The anti-HBs titers were decreased in 51.8% (44/85) of vaccinee. The GMT was 80.04 mIU/ml. The protective rate and GMT were 98.0%, 129.43 mIU/ml in the group with anti-HBs titer ≥50 mIU/ml at 1 month after vaccination, and 64.71%, 19.62 mIU/ml in the group with anti-HBs <50 mIU/ml. Conclusion : Green Cross HG-II vaccine is safe and effective in protecting hepatitis B at 0-1-2 months vaccination schedule. However, the booster injection should be recommended for maintenance of immunogenicity, especially in the vaccinee with anti-HBs titer less than 50 mIU/ml at 1 month after vaccination.(Korean J Med 58:12-18, 2000)