Both US and EU Preferential Trade Agreements (PTAs) nowadays consistently contain social standards to protect workers and the environment. But while the US pursues a sanction-based approach, the EU solely relies on dialogue and cooperation mechanisms. This book attempts to explain what has led the US and the EU to pursue such diverging approaches. In a structured comparison, this study analyses the US' and the EU's PTA negotiations with Central America, Peru and Colombia, and South Korea. Empirical findings suggest that the constellation of societal preferences was fairly similar in the US and Europe. However, the different institutional frameworks in the US and the EU translated these societal demands into different policy outcomes. In short, the features of the US' domes-tic political processes were much more favourable to the formation of sanction-based social standards than the consensus-oriented style of policymaking in the EU.