Nataliya Esakova performs an analysis of the interdependencies and the nature of cooperation between energy producing, consuming, and transit countries, focusing on the gas sector. For the analysis, the theoretical framework of interdependence theory by Robert O. Keohane and Joseph S. Nye, as well as international regime theory, are applied to the recent developments within the gas relationship between the European Union and Russia over the last decade. The objective of the analysis is to determine whether a fundamental regime change, in terms of international regime theory, is taking place and, if so, which regime change explanation model, in terms of interdependence theory, is likely to apply.