Participation rates of health care workers in voluntary free hepatitis B virus immunization programs are 35% to 40%. University teaching hospital employees at risk for hepatitis B virus and presenting for immunization were surveyed as to vaccine preference. Both plasma-derived and recombinant hepatitis B virus vaccines were available. During a 10-month period, 173 health care workers enrolled in the study. One hundred seventeen received recombinant vaccine, and 56 received plasma-derived vaccine; 66 were immunized postexposure. Concern of a relationship of human immunodeficiency virus to hepatitis B virus plasma-derived vaccine was acknowledged by a small number of health care workers as important in vaccine selection. Recombinant hepatitis B virus vaccine rapidly and substantially supplanted plasma-derived vaccine but did not increase program participation. We suspect that mandatory immunization or proof of immunity will be necessary ifhepatitis B virus protection rates in health care workers are to improve.