Why has autonomy been a leading idea in philosophical writing on bioethics, and why has trust been marginal? In this important book, Onora O'Neill suggests that the conceptions of individual autonomy so widely relied on in bioethics are philosophically and ethically inadequate, and that they undermine rather than support relations of trust. She shows how Kant's non-individualistic view of autonomy provides a stronger basis for an approach to medicine, science and biotechnology, and does not marginalize untrustworthiness, while also explaining why trustworthy individuals and institutions are often undeservingly mistrusted. Her arguments are illustrated with issues raised by practices such as the use of genetic information by the police or insurers, research using human tissues, uses of new reproductive technologies, and media practices for reporting on medicine, science and technology. Autonomy and Trust in Bioethics will appeal to a wide range of readers in ethics, bioethics and related disciplines.