Personnel at high risk of acquiring hepatitis B in two university-affiliated teaching hospitals were offered immunization against this disease. Of the 1,193 employees, 454 (38%) requested immunization. Individuals who declined or deferred immunization were sent questionnaires requesting the reasons for their decisions. Responses to the questionnaire were received from 487 of 674 personnel (72%). Most respondents (>90%) indicated that they: 1) were aware of being at risk of acquiring hepatitis B, and 2) recognized the potential danger of the disease. A majority of respondents (56%) indicated that they had decided not to be immunized because they wanted to wait until more was known about the vaccine. Concern about specific side effects (eg. Guillain-Barre syndrome or acquired immunodeficiency syndrome) was cited much less often as a reason for declining immunization. Nearly one-fifth of questionnaire respondents either did not know the date of their last tetanus-diphtheria immunization or had not received a booster within the past decade.