Bioethicists tend to focus on the individual as the relevant moral subject. Yet, in highly complex and socially differentiated healthcare systems a number of social groups, each committed to a common cause, are involved in medical decisions and sometimes even try to influence bioethical discourses according to their own agenda. We argue that the significance of these collective actors is unjustifiably neglected in bioethics. The growing influence of collective actors in the fields of biopolitics and bioethics leads us to pursue (...) the question as to how collective moral claims can be characterized and justified. We pay particular attention to elaborating the circumstances under which collective actors can claim ‘collective agency.’ Specifically, we develop four normative-practical criteria for collective agency in order to determine the conditions that must be given to reasonably speak of ‘collective autonomy’. For this purpose, we analyze patient organizations and families, which represent two quite different kinds of groups and can both be conceived as collective actors of high relevance for bioethical practice. Finally, we discuss some practical implications and explain why the existence of a shared practice of trust is of immediate normative relevance in this respect. (shrink)