This thesis analyses the EU´s external energy security policy through a comparative analysis of the energy relations between the EU and important producers of natural gas; Russia, Norway, the Mediterranean, Gulf and Caspian region. In order to detect variation in the policy, three strategies the EU can pursue in order to enhance its energy security are derived based on the debate between realism, economic and institutional liberalism around necessary means to strengthen an energy consumer’s supply security. The analysis reveals that the EU relates itself differently to the producers in terms of what strategy it makes use of and the effort it puts behind each of the instruments; as such there is variation in the external energy security policy of the EU. Overall, the EU has put most effort into those strategies that aim at market creation and institutionalisation of the relationship. This was expected given the nature of the EU as a foreign policy actor, and the status of energy policy at Community level. Nevertheless, the pattern is a bit more nuanced as several political strategic instruments also are detected. It was assumed that certain characteristics of the producers, such as regime type, level of resource richness, degree of interdependence with the EU and conflict level would contribute to an explanation of this variation. Yet, the comparative analysis reveals that they are not adequate as explanatory factors, and other factors have been pointed to, such as perceptions of supplier role, transit potential, geographical proximity, strategic importance in terms of security, crisis management and diversification, along with resource richness to some degree at the regional level. The findings indicate that the EU aims to enhance its energy security along several dimensions, and that various external factors can contribute to explain its external energy security policy.