Markers of hepatitis B (HBsAg, anti-HBs) and C (anti-HCV) were detected in 1990-1992 by enzyme immunoassay in 1581 medical workers, 230 last-year students of medical schools, 269 patients hospitalized at hemoperfusion wards, and 701 blood donors. Hepatitis B markers were detected in medical workers two times more frequently than in donors (HBsAg in 4.7 and 2.2% of these, respectively, anti-HBs in 26.2 and 14.0%), and anti-HCV were found almost three times more frequently (in 3.1 and 1.1%, respectively). The incidence of these markers in students of medical schools was the same as in donors. Hepatitis B markers (HBsAg, anti-HBs) were detected in 39.0% of patients of hemoperfusion departments, HBsAg being present in 11.9%, and antiHCV in 25%. A direct relationship was revealed between the incidence of hepatitis B and C markers and duration of treatment at dialysis centers or length of service at therapeutic institutions. Three vaccinations with Engerix B 944 vaccine were administered to 944 medical workers and 162 medical students and four vaccinations in double doses to 40 patients of hemoperfusion centers who had no hepatitis B markers; a month after immunization anti-HBs in protective titers were detected in 91.4, 93.9, and 76.1% of them, respectively, and a year after vaccination these values were 77.2, 82.5, and 53.3%. No cases of hepatitis B, detection of HBsAg, or postvaccination complications in the vaccines were recorded.