Modern trade agreements no longer emphasize basic trade liberalization but instead focus on international policy coordination in a much broader sense. In this review we introduce the emerging literature on the political economy of such deep integration agreements. We organize our discussion around three main points. First, the political conflict surrounding trade agreements is moving beyond the classic antagonism of exporter interests who gain from trade and import-competing interests who lose from trade. Second, there is a more intense popular backlash against deep integration agreements than there was against shallow integration agreements. Finally, the welfare economics of trade agreements has become more complex, in the sense that the goal of achieving freer trade is no longer sufficient as a guide to evaluating the efficiency of international agreements.