There is no evidence up to now that the currently available plasma hepatitis B vaccine transmits the agent of AIDS. To support further the safety of this vaccine we examined 137 vaccinees for the presence of antibodies to LAV/HTLV-III. Three groups had received Merck, Sharp and Dohme hepatitis B vaccine (two groups of 25 Air Force cadets vaccinated with investigational lots and 18 multiply transfused children vaccinated with a commercial lot); another two groups (50 Air Force cadets and 19 multiply transfused) were vaccinated with two commercial lots of Institut Pasteur vaccine. Sera were collected before inoculation, 7 and 24 months later. Enzyme linked immunosorbent assay was used for the detection of antibodies to LAV/HTLV-III. Positive sera were tested again by Western Blot and Radioimmune Precipitation Assay to exclude non-specific binding. Antibodies to LAV/HTLV-III were not detected in any of the sera examined, providing evidence for safety. We believe that these data increase the acceptance of hepatitis B vaccine.