Power and choice represent two fundamental forces that govern human behavior. Scholars have largely treated power as an interpersonal construct involving control over other individuals, whereas choice has largely been treated as an intrapersonal construct that concerns the ability to select a preferred course of action. Although these constructs have historically been studied separately, we propose that they share a common foundation — that both are rooted in an individual's sense of personal control. Because of this common underlying basis, we hypothesized that power and choice are substitutable; that is, we predicted that the absence of one would increase the desire for the other, which, when acquired, would serve to satisfy the broader need for control. We also predicted that choice and power would exhibit a threshold effect, such that once one source of control had been provided (e.g., power), the addition of the other (e.g., choice) would yield diminishing returns. Six experiments provide evidence supporting these predictions.