Since their origins in seventeenth-century Sweden, population registers have been kept at local level, and computerization has now made it possible to establish national registers in most of the 30 European countries analysed in this article. As a result of these registers, the production of demographic statistics has entered a new era, with many advantages but also ethical controversies. New questions arise, such as the definition of residents, double counting and data confidentiality. This article describes and compares the operational principles of central registers in various countries, and how individual data are extracted in order to produce demographic statistics. It is now possible to regularly monitor the individual demographic trajectories of the entire population at national level, and to reveal interactions between the demographic behaviours of individuals in a single household. Given the many opportunities afforded by longitudinal analysis, support from researchers would be particularly beneficial, and efforts must be made to facilitate access to individual data.