Introducing a new medical technique, procedure or drug to the public via clinical trials is risky at the best of times. When the trial involves a biotechnology which holds out the promise of prolonging, if not saving, life the push to move from the laboratory to clinical trials may be hard to resist. In this article I explore whether the regulatory scheme for clinical trials in the UK is able to accommodate developing technologies by considering how the current legal and ethical frameworks determine when a procedure such as xenotransplantation should proceed to trials. In particular, I discuss whether basing our regulatory schemes on the principles espoused in the Declaration of Helsinki offer sufficient protection to those who may be affected by xenotransplant trials – the recipient, their health-care workers, close contacts and, unusually, the wider public. I question whether it is possible for a technology to be approved for clinical trials when allowing such trials may benefit the individual but ultimately negatively impact on society as a whole.