This chapter argues that the use of capacities to determine the ethical legitimacy of xenotransplantation procedures is problematic. The impetus to consider xenotransplantation as a viable treatment option in the future remains clearly grounded in the possibility that, even were less controversial sources of organ transplantation to be maximized, there would remain a shortage of organs for transplantation. The ethical acceptability of xenotransplantation is dominated by two issues: whether its use of animals is acceptable and whether its contribution to public health is likely to outweigh any harm it may cause. The legal, ethical and scientific problems associated with xenotransplantation might make the notion of calling a halt appealing, either in the short term or indeed permanently. Both the Nuffield Report and the Kennedy Report recommended the establishment of a National Standing Committee, which was satisfied with the creation of United Kingdom Xenotransplantation Interim Regulatory Authority.