PURPOSE: Although the term "responsibility" plays a central role in bioethics and public health, its meaning and implications are often unclear. This paper defends the importance of a more systematic conception of responsibility to improve moral philosophical as well as descriptive analysis. METHODS: We start with a formal analysis of the relational conception of responsibility and its meta-ethical presuppositions. In a brief historical overview, we compare global-collective, professional, personal, and social responsibility. The value of our analytical matrix is illustrated by sorting out the plurality of responsibility models in three cases (organ transplantation, advance directives, and genetic testing). RESULTS: Responsibility is a relational term involving at least seven relata. The analysis of the relata allows distinguishing between individual versus collective agency, retrospective versus prospective direction, and liability versus power relations. Various bioethical ambiguities result from insufficient, implicit, or inappropriate ascriptions of responsibility. CONCLUSIONS: A systematic conception of responsibility is an important tool for bioethical reflection. It allows an in-depth understanding and critique of moral claims on a meta-ethical level without presuming one particular normative approach. Considering the concept of responsibility can also help to complement the current bioethical focus on individual autonomy by including the perspectives of other actors, such as family members or social groups.