This book examines when, how, and why internationalisation affects national economic institutions. It confronts questions at the heart of debates in political economy and comparative politics: What does internationalisation of markets mean? Who are its carriers in domestic arenas? Throughwhich mechanisms does it affect decisions about national institutional reform? What are the patterns of institutional outcomes in the face of internationalisation?To respond to its questions, the book looks at developments in five strategic sectors: securities trading, telecommunications, electricity, airlines, and postal services. It compares four countries, each representing a different 'variety of capitalism', namely Britain, France, Germany, and Italy,over the period between 1965 and 2005. Thus it combines cross-national, historical, and cross-sectoral comparisons.The author distinguishes technological and economic forms of internationalisation from policy forms, namely regulatory change in powerful overseas nations and by the EU. He shows that, contrary to expectations, the first made little impact, whereas regulatory reforms by the US, Britain, and the EU,undermined long-standing national institutions. They did so by aiding governments to build and lead reform coalitions, through increasing fears of regulatory competition, offering occasions for reconsideration of existing institutions and providing legitimation for new ones. Whilst the impacts ofpolicy forms of internationalisation varied across nations, giving rise to diverse reform paths, the overall institutional outcomes were that all four countries adopted increasingly similar reforms of economic institutions. This book rejects the view that technological and economic forms of internationalisation drive institutional change in and of themselves. Instead it shows that policy forms of internationalisation are influential because they become part of domestic decision making and thereby spur reform, even ofdeeply-entrenched national institutions.