In recent years we observed 3 lethal primary varicella infections in adult kidney transplant recipients. Therefore, we wondered how many of our adult renal transplant patients were not protected against varicella zoster virus (VZV), and therefore were at risk for such a primary infection. We also studied the prevalence of VZV seronegativity in the adult patients on our waitlist for kidney transplantation. Finally, we vaccinated these seronegative patients with an attenuated live vaccine. Sera were obtained from 854 transplanted patients, and from 286 candidates on the waitlist for kidney transplantation. We observed that 2.1% of our renal transplant recipients and 3.2% of the patients on the waitlist were seronegative for VZV. We vaccinated 11 seronegative patients on the waitlist twice without side effects. In 7 of 11 patients this resulted in a positive serologic response. In conclusion, the prevalence of VZV seronegativity was low both in renal transplant recipients (2%) and in patients on the waitlist (3%). Vaccination of transplant candidates resulted in a moderate efficiency of 64%.