The risk of acquiring hepatitis associated with work in a moderate-sized acute-care teaching hospital was determined by a seroepidemiologic survey of hepatitis B surface antigen and antibody. A blood specimen and a completed questionnaire were obtained from 76 percent of the staff members involved in patient care activities and all preemployment applicants (a total of 767 persons). One employee was found to have transiently positive tests for hepatitis B surface antigen, whereas 94 (12.2 percent) were found to have hepatitis B surface antibodies. Using the national incidence rate for volunteer blood donors of 4.4 percent as a norm, significantly higher antibody incidence was seen in nursing personnel (16.9 percent), laboratory workers (14.0 percent), surgeons (37.5 percent) and dental workers (40.0 percent). Rates were not significantly raised among house officers, internists, respiratory therapists or housekeeping employees. Increased incidence was statistically related to age and known history of hepatitis, but not to sex, known needle-stick exposure, contact with patients having hepatitis, prior blood transfusion, blood handling or nonhospital exposure to hepatitis. In persons whose tests were positive for antibodies there was a 4 percent increment per decade of age among long-term employees; duration of employment approached significance as a risk factor. Of those with hepatitis B antibody, only 16 percent were aware of a prior bout of hepatitis.