The results of hepatitis B vaccination (H-B-VAX, 1 ml = 20 micrograms HBsAg, scheme 0, 1, 6) in nine susceptible health care workers of hemodialysis unit are described. Seroconversion was achieved in 100% of recipients. The mean titer of anti-HBs was 11,691 mIU/ml at three years, 5,879 mIU/ml at four years and 2,770 mIU/ml at five years after the beginning of vaccination. H-B-VAX vaccine (first dose 40 micrograms HBsAg, second and third = 20 micrograms) was administered in three patients on hemodialysis (scheme 0, 1, 2). In all of these patients, seroconversion occurred (titers of anti-HBs from 23 to 104 mIU/ml). Of the 55 workers of dental units, nine (16.4%) showed signs of previous HBV infection. Twenty were vaccinated with H-B-VAX vaccine (scheme 0, 1, 2) and of these patients one (5%) was nonresponder, two (10%) poor responders, 13 (65%) good responders and four (20%) excellent responders, with the mean anti-HBs titer of 1,540 mIU/ml. Seven dental workers received recombinant vaccine also using a scheme 0, 1, 2. Four (57%) of these workers were poor responders, and three (43%) good responders, with the mean anti-Hbs titer of 168 mIU/ml. All of our vaccinated subjects had no serious side effects except local soreness at the injection site. Thus, vaccination against hepatitis B in health care personnel and other high-risk patients may control efficiently the spread of HBV infection.