Important progress has been made in recent years in the valuation of social costs of energy and transport. This progress has encouraged the insight that systems of "Green Accounting" considering social costs and policy instruments for the internalization of social costs are necessary tools to realize the worldwide goal of sustainable development. This workshop report provides an excellent survey of the latest results of social costs in the energy and transport sector. Further, the theoretical framework of social costs is extended to a broader concept of sustainable development. Finally, concepts and first experiences of the internalization of social costs e.g. through least cost planning or an ecological tax reform are reviewed.