The present study was designed to assess the risk of hepatitis B virus (HBV) infection among hospital employees, who often contract the infection before the beginning of their employment, and to suggest a prevention strategy. The study population consisted of 2518 subjects working or studying at the two Hadassah University hospitals, on Mount Scopus and at Ein Kerem in Jerusalem. The total prevalence for anti-HBc positivity as an indicator for past or present HBV infection was 17.6%. Several variables, including country of birth, age, and duration of employment significantly affected the rate of anti-HBc positivity. The highest rates for anti-HBc+ were found in personnel of selected departments such as haemodialysis (31.8%), haematology/oncology (28.3%), and the blood bank (24.0%), after adjustment for country of birth, age, and sex. Specific occupations in the hospital were associated with an increased rate of anti-HBc positivity. Thus the highest rate of HBV infection (after adjustment for country of birth, age, and sex) was shown for housekeepers (32.4%) and departmental secretaries (23.6%), who take care of waste products containing blood, or who transfer vials containing blood to the hospital laboratories. By comparison, anti-HBc was positive in 17.2% of nurses, 15.6% of physicians, and only 7.8% of administrative clerks. Israel is a country of immigration, and anti-HBc rates were four times higher in employees born in countries where HBV is more endemic--for example, in north Africa and Mediterranean countries--than in employees born in western Europe or the United States. However, rate of anti-HBc + increased significantly with age as well as duration of employment in the hospital, irrespective of country of birth. These data indicate that although HBV infection often occurs in Israel before commencement of employment in the hospital, hospital employees are at significant risk for contracting HBV infection during their professional lifetime regardless of where they were born. Moreover, paramedical personnel such as housekeepers and departmental secretaries are in the highest risk group for contracting HBV. Finally, as a result of the high background of anti-HBC positivity in selected ethnic groups, mandatory screening for anti-HBc before employment in medical institutions in Israel is recommended for them, then active vaccination against HBV for employees at risk. Employees who immigrated from western Europe and the United States should be immunised without pre-vaccination screening for HBV.