Abstract
As clinical trials in xenotransplantation commence, the question of whether participants may withdraw from research is being intensely debated. Some authors argue that xenotransplant recipients should be subject to lifelong monitoring because of the potential risk of zoonotic or xenozoonotic infections affecting third parties. Others maintain that the right to withdraw from research participation is a fundamental principle of medical ethics that must not be compromised. To clarify this tension, historical precedents have been examined, and the applicability of so-called Ulysses contracts to xenotransplantation has been critically assessed. The practical answer is more straightforward than the theoretical debate suggests: xenotransplant recipients, like allotransplant recipients, require continuous medical supervision. Lifelong immunosuppression and regular follow-up are essential to preserve transplant function and, ultimately, the patient's life.