Portugal and Spain have been at the heart of European history and have played a critical role in European (and world) affairs throughout the centuries. Yet decades of relative isolation under authoritarian regimes in the twentieth century left both countries at the margins of Europe, and they did not take part in the early stages of the process of European integration in the 1950s–70s. Fortunately, the success of processes of democratic transition in both countries in the second half of the 1970s paved the way for full membership in the European Community (EC).I would like to thank the participants in the conference “Towards the Completion of Europe” held at the University of Miami on April 2005, and in particular to Dr. Joaquín Roy for all his advice and support. This is an updated version of a paper that I presented at the conference published in Royo 2006. I would like to thank Jeffrey Kopstein, Ramón de Miguel, Kalypso Nicolaidis, George Ross, and Francisco Seixas da Costa for their valuable comments during the last roundtable of the conference From Isolation to Europe: 15 Years of Spanish and Portuguese Membership in the European Union at the Minda de Gunzburg Center for European Studies, Harvard University, November 2–3, 2001. See also Royo 2003.