Liberal international relations theory posits that the behaviour of states is affected both by domestic interests and other states with which they are linked in significant patterns of interdependence. This article examines the relevance of this proposition to states' behaviour in the most powerful institution in the furthest reaching example of regional integration in the world today: the Council of the European Union. Compared to previous research, more detailed evidence is analysed in this article on the substance of the political debates that preceded Council votes. It is found that states' disagreement with both discretionary and nondiscretionary decision outcomes affects the likelihood that they dissent at the voting stage. Moreover, in line with the theory posited here, the behaviour of states' significant trading partners has a particularly marked effect on the likelihood that they will dissent.