The centuries-old Westphalian state system has never resolved the tension between the principle of the sovereign equality of states and the idea that great powers enjoy certain privileges and bear special responsibilities. Here, a team of American and European scholars makes one of the best efforts yet to identify the norms of hegemonic and great-power responsibility by examining three “problem areas” in contemporary world politics: nonproliferation, climate change, and international financial regulation. They find that problem solving in the post–Cold War international system has been accomplished not by appeals to the sovereign equality of states nor by the outright imposition of order by dominant countries. Rather, states have sought to establish a middle ground, in which the United States and other great powers are given more say over rules and institutions but are expected, in return, to make costly commitments and shoulder disproportionate burdens. It is a classic bargain: great powers are granted the legitimacy to exercise power on the global stage, but the price is a willingness to act—at least at the margins and consistent with their self-interest—for the common good.