Of the thirty-two risk factors analyzed for possession of HBV serum markers, the significant factors, in order of importance, were: age, intravenous drug use while not incarcerated, intravenous drug use while incarcerated, race, education, military service history and duration of any imprisonments. Mass immunization of inmates against HBV does not seem warranted due to the small contribution of incarceration to overall risk. At high risk are inmates with long sentences or those who use intravenous drugs in prison. A serological screening and immunization program can be targeted with the logistic model. Tables include information on seroepidemiology of Hepatitis A, 26 references. (Author abstract modified)