Many regions of the world feel the pressure to interconnect electric power systems internationally. Regional integrations of the electricity sector have become part of free trade and common market initiatives, though the steps individual national jurisdictions take towards developing integrated systems vary. In this article. we review three regions concerned with common market initiatives and at different stages of integration processes that involve infrastructural, regulatory, and commercial decisions. First, we examine the North European countries in the Nordic Council, then countries in the Southern Cone of South America in MERCOSUR, and finally Mexico. the United States and Canada, linked under NAFTA. This comparative Study highlights the potential, but also the many hurdles, that electricity sector integrations face. The study suggests a framework for measuring the level of electricity sector integration that could be applied to other regions. (C) 2003 Elsevier Ltd. All rights reserved.