This essay asks what it is about the practice of trade that grounds duties of justice between states as trade partners. The answer advanced is that such duties are grounded in the dependence that trade generates. The essay puts forward four conditions that a plausible account of grounding in trade must meet: it must admit of degrees, explain the distinctly international character of trade justice, ground both procedural and distributive duties, and it must be a necessary feature of all trade (...) relationships which generate duties of justice. A dependence account of grounding meets all four conditions, and does so in an intuitively compelling way. While other accounts of what grounds duties of trade justice can meet some of the conditions, none can meet all of them. Relative to rival candidates, then, the dependence account provides a firmer foundation for the ongoing attempts to develop a comprehensive theory of trade justice. (shrink)