Hospital staff members were analyzed with respect to ethnic origin and prevalence of anti-hepatitis B surface antibodies (Anti-HBs). The staff members were categorized into four "risk groups" according to frequency of exposure to blood, patients' speciments, and patient care. Of the total 526 staff members studied, one-half (51.5%) were of North American origin, one-quarter came from Europe (25.9%), and the rest came from Asia, the West Indies, Africa, and Australia. The prevalence of Anti-HBs was lowest among North American staff members (8.1%) and highest among Asians (42.3%) (P less than or equal to 0.05). Low-risk administrative staff had the significantly lowest number of Anti-HBs-positive members (6.1%), whereas low-risk dietary staff (29.6%) and hospital assistants (30.6%) had the significantly highest prevalence of Anti-HBs staff members. In contrast, the high-risk group of laboratory workers and special nurses had only 16.1% of staff members with Anti-HBs. Our results show that ethnic background and socioeconomic conditions have to be considered when various risk groups are compared for the presence of Anti-HBs. The frequency of exposure to blood and patients' specimens or patient care is not the only determining factor in the prevalence of Anti-HBs in health workers.