Sixty-five HIV-infected patients received high-dose (40mug), short interval HBV vaccine. In non-responders to the initial immunization, 1-3 boosters were administered. Rate of response was 60.0% after primary vaccination, and 89.2% after boosters. However, 12 and 24 months after the last vaccination, only 63% and 32.7% of the responders, respectively, had persistence of protective anti-HBs titers (> or =10 IU/L). The results of logistic regression show that gender, CD4 count, and HIV viral load were significant predictors of vaccination outcome. This study suggests that in HIV-infected patients with relatively high CD4 count, response to high dose of HBV vaccine is suboptimal. Rate of response may be increased by vaccine boosts, but antibody titers are significantly lower in non-responders than in responders to primary vaccination. Since persistence of anti-HBs titers appears significantly related to antibody titers after the immunization procedure, monitoring of anti-HBs, particularly in patients with low level of protective antibody titers after primary vaccination or boosters, seems more than justified.