SUMMARY: Four hundred and twenty one sera samples collected during 1995 to 1997 from subjects at high-risk for HBV infections were tested for the presence of HBV markers. The subjects included kidney transplants (n=109), hemodialyzed patients (n=76), non-vaccinated healthcare workers (n=52) and blood transfusion dependent patients (n=80). Blood transfusion dependent patients include 60 thalassemic, 6 hemophilic and 14 sickle cell anemia patients. HBsAg prevalence rates of 29.4%, 17%, 22.5% and 9.6% were observed among kidney transplant, hemodialysis, blood transfusion dependent patients, and non-vaccinated healthcare workers, respectively. HBeAg prevalence rates among HBsAg positive subjects of the previous groups were 43.8%, 76.9%, 38.9% and 0.0%, respectively. Our study indicates that 76.9% of HBsAg positive hemodialysis patients and 43.8% of HBsAg positive kidney transplant patients are highly contagious and constitute a high risk factor for the spreading of this infection. The prevalence rates of anti-HBc, previous infection rates of 56.9%, 50.0%, 37.9% and 17.3% were observed among kidney transplant, hemodialysis, blood dependent patients, and non-vaccinated healthcare workers, respectively. These results show that HBsAg in these high risk groups is high and vaccination against HBV of these groups is recommended.