This paper discusses the structural and regulatory changes that are affecting electricity sectors around the world. The direction of change is toward promoting competition in the supply of generation services, restructuring of electricity supply enterprises to clearly separate the provision of competitive generation services from monopoly transmission and distribution services, and the application of new regulations governing access to the transmission and distribution networks and the associated costs of the services provided by these networks. The potential impacts of these changes on electricity costs and prices, economic development, the distribution of income, the choice of generating technologies, research and development and the environment are discussed. Differences in the current performance and the likely future impacts of electricity sector restructuring on developing and developed countries are discussed.