What are the economic effects of the internationalization of infrastructures? We have addressed this question at the 12th Annual International Conference on the Economics of Infrastructures (Delft, May 2009). Internationalization of infrastructures refers to the increasing network interconnections of infrastructures across borders, and, as a consequence, the creation of international organization to operate them, and the development of international institutions to govern them. These proceedings compiles contributions on the industrial sectors of oil and gas, electricity, telecommunications, water and railways. In addition, they include a section on the history and another on future perspectives of the internationalization of infrastructures.