We compared the efficacy of intramuscular (im) and intradermal (id) administration of vaccine against HBV. Only one out of 25 im vaccinated subjects did not respond whereas all 25 id immunized persons developed anti-HBs above 10 IU/l. The mean serum level of anti-HBs in im and id vaccinated group was 2351 +/- 2358 IU/l and 1823 +/- 1502 IU/l, respectively (p = 0, 382; NS). It seems that the efficacy of both vaccine administration is very similar.