In this chapter, we provide essential background information that is necessary to understand what is at stake in the process of pension market integration. National pension systems are under pressure due to unfavorable demographic developments, financial constraints, and new social risks that are not covered by many traditional pension plans. These pressures politicize workplace pensions in new ways and differently across divergent types of pension regimes. This creates dilemmas for would-be reformers in Europe. On the one hand, the EU-wide harmonization of workplace pension regulations is attractive for large corporations in Europe because compliance with a single regulatory framework is easier and more cost-effective than compliance with twenty-seven different regulatory systems. Individuals also stand to gain from pension market integration since they would no longer lose pension benefits and rights if they moved across borders. On the other hand, even a partial harmonization of pension regulations at the EU level produces winners and losers since certain pension regimes are inherently better suited to accommodate EU-mandated change than others. Thus, the creation of a single pension market represents a classic cooperation problem: converging on common rules is desirable in principle, but deep divisions exist over objective and means of harmonization. Countries facing high costs of adjusting to EU directives will seek to keep the pain of reform to a minimum. This makes any common policy hard to adopt.