Recent philosophical inquiry into the relations thought to metaphysically structure the world has largely focused on the notion of metaphysical grounding, whereas previously analytic metaphysicians tended to talk in terms of ontological dependence. This raises the question of how metaphysical grounding and ontological dependence relate to one another. In this article, I sketch a picture of grounding as a form of metaphysically substantive sufficient condition and ontological dependence as a form of metaphysically substantive necessary condition, anchored in widely accepted principles (...) for how these relations work. As a case study, I apply this picture to Jack Casey's recent attempt to reduce ontological dependence to a special case of grounding. I argue that Casey's account fails and I show how the picture of grounding and ontological dependence presented here helps us diagnose where the account goes wrong, as well as how it makes sense of the phenomena Casey's account struggles with without having to resort to any ad hoc maneuvers. Thinking of grounding as a form of metaphysically substantive sufficient condition and ontological dependence as a form of metaphysically substantive necessary condition is thus shown to help sharpen our understanding of these phenomena and provide minimal constraints on any purported reductive account of one of the phenomena in terms of the other. (shrink)