The idea that payment for research participation can be coercive appears widespread among research ethics committee members, researchers, and regulatory bodies. Yet analysis of the concept of coercion by philosophers and bioethicists has mostly concluded that payment does not coerce, because coercion necessarily involves threats, not offers. In this article we aim to resolve this disagreement by distinguishing between two distinct but overlapping concepts of coercion. Consent-undermining coercion marks out certain actions as impermissible and certain agreements as unenforceable. By contrast, (...) coercion as subjection indicates a way in which someone’s interests can be partially set back in virtue of being subject to another’s foreign will. While offers of payment do not normally constitute consent-undermining coercion, they do sometimes constitute coercion as subjection. We offer an analysis of coercion as subjection and propose three possible practical responses to worries about the coerciveness of payment. (shrink)