This paper introduces the objectives and basic approach of a collaborative comparative research project on the introduction of national electronic Identity Management Systems (eIDMS) in Member States of the European Union. Altogether eight country case studies have been produced in two waves by researchers in the respective countries, which will be presented in the following articles in this special issue. The studies adopt a common conceptual framework and use the same terminology, which will be presented in this introduction, just as (...) the reasoning for the selection of the particular countries under investigation. The conceptual framework combines elements of actor centred institutionalism with path analysis, looking for path continuation, change or creation in the transition from the previous IDMS to an electronic one and explaining this as choices of actors in certain contexts. Information on the reasons for these choices in the first four cases has been collected from in depth interviews with key actors and in the four other cases from official documents. As the subject of this research is the transition of national identity management systems only countries have been included in which a national ID and a civil registry already exist before the introduction of the electronic elements, thus excluding the UK. (shrink)