To determine the efficacy of an additional low dose of intradermal injection of recombinant HB vaccine administered to nonresponders in addition to the standard three injections, we investigated the anti-HBs positive rate and titer of anti-HBs after four years among 58 subjects who did not develop antibodies after three doses of subcutaneous injections and who did develop the antibody after an additional low dose intradermal injection (Nonresponders), and compared them with 150 subjects who developed anti-HBs after three doses of subcutaneous injections (Responders). Fifty four subjects who were negative after four years were revaccinated with one or three doses of the subcutaneous injection. Anti-HBs positive rates after four years were 56.0 percent in Responders and 56.9 percent in Nonresponders, showing no differences. Eighty eight percent of 54 subjects who were given one or three doses of the vaccine developed anti-HBs. There were no differences in the antibody rates or titer of the antibody between the one and three doses groups. The decrease in titer of antibody was related to the levels initially having the most marked decrease in the level four years later. From these findings, we concluded that there were no differences of anti-HBs positive rates or antibody titer after four years in Responders and Nonresponders, and that one additional dose of the vaccine may be effective four years after initial administration among both groups.