The antibody response of immunosuppressed heart transplant recipients to vaccination with the hepatitis B (HB) virus vaccine Hepa Gene 3 (HG-3), containing HB virus pre-S1, pre-S2, and S gene products, was examined. Three heart transplant recipients who had been vaccinated preoperatively against HB responded well to the vaccination. Five of 38 patients (13.2%) vaccinated postoperatively before HG-3 vaccination with the second-generation vaccine Gen-H-B-Vax-D (37 without and 1 with detectable anti-HBs response) and 3 of 24 (12.5%) without previous HB vaccination developed protective anti-HBs titers (greater than 10 U/l) after immunization with the HG-3 vaccine. The low response rate (8/62, 12.9%) found for postoperatively vaccinated patients indicates that heart transplant recipients should be vaccinated against HB before immunosuppressive medication.