Clinical trials in xenotransplantation (XTx) that have just started to fulfil a long delayed promise should certainly be performed under the same guarantees for the subjects involved as any other experimentation in human medicine. The most important is the absolute respect for their fundamental rights and freedoms, especially for their autonomy, which is expressed through their informed consent as essential requirement for the carrying out of any clinical trial. This chapter focuses on the legal and ethical adaption of the clinical trial’s general rules to the particular conditions of xenografting. They are mainly related to the possibility that transmissible xenogeneic agents come into being and become a risk for third parties, even for the whole society. This aspect makes XTx different from any other therapy in (bio)medicine. According to most literature and norm proposals, such xenogeneic infection risk would justify important changes in clinical trial regulation: last but not least, it could mean fundamental right limitations for the xenografted subjects. However, an analysis of the present ethical and legal background at national and international levels shows that such special treatment would be awkwardly acceptable. Information and recommendations on XTx and on its chances and risks when consenting to the trial would be more advisable than right constraining approaches.