This paper explores some ways in which Immanuel Kant’s ethical theory can be brought to bear on professional and health care ethics. Health care professionals are not mere individuals acting upon their own ends. Rather, their principles of action must be defined in terms of participation in a cooperative endeavor. This generates complex questions as to how well their roles mesh with one another and whether they comprise a well-formed collective agent. We argue that Kant’s ethics therefore, and perhaps surprisingly, requires us to consider the institutions, procedures, and politics that decide who should play what part in a complex collective enterprise. Likewise, professional responsibility involves – alongside a readiness to play one’s individual part – a concern for these collective aspects of healthcare.