What kind of patients may be recruited to early clinical trials of xenotransplantation? This is discussed under the assumption that the risk of viral infection to the public is non-negligible. Furthermore, the conditions imposed by the Helsinki declaration are analysed. The conclusion is that only patients at risk of dying and with no alternative treatment available should be recruited to xenotransplantation trials in the early phase. For some of the less dangerous cell or islet cell xenotransplantation other categories might be (...) recruited. The risk of cell and islet cell xenotransplantation should, however, be weighted against the development of other technologies.In order to safeguard the public, the opt-out clause in the Helsinki declaration should not be fully applied. Legally binding rules on obligatory monitoring and restrictions should be imposed—before clinical trials start. Journal of Medical Ethics. (shrink)