The immune response of 32 haemodialysis patients vaccinated with a recombinant yeast-derived hepatitis B vaccine (YHB vaccine) was compared with that of healthy adults and of another haemodialysis patient group vaccinated with the plasma-derived vaccine (PHB vaccine). Twenty-two patients were immunized 3 times (months 0, 1 and 6) intramuscularly with a 20 micrograms dose, and ten patients with a 40 micrograms dose of the YHB vaccine. All members of the former group (100%) and nine of the latter group (90%) were anti-HBs positive after 3 vaccinations (months 7); anti-HBs concentrations with geometric mean titres (GMTs) of 82.3 mIU/ml and 242.1 mIU/ml, respectively, the difference being statistically in significant. The 87 healthy control group participants were vaccinated according to the same schedule but with 10 micrograms per dose, and 98% of them were anti-HBs positive by month 7, with a GMT of 198.3 mIU/ml. The patients responses were higher at each time point than those of 53 dialysis patients vaccinated in an earlier study with either 20 micrograms or 40 micrograms PHB vaccine. Two additional inoculations led to a substantial elevation of the anti-HBs titre in most of the haemodialysis patients; GMTs by month 12 being 506.8 mIU/ml and 979.5 mIU/ml for the 20 micrograms and the 40 micrograms dose respectively. No serious side-effects were observed over the one-year period of study. From these results, it was concluded that the YHB vaccine is highly immunogenic and could replace the PHB vaccine even in dialysis patients.